EVALUATION KIT AVAILABLE

Click here for production status of specific part numbers.

MAXM86161 Single-Supply Integrated Optical Module

for HR and SpO2 Measurement

General Description Benefits and Features

The MAXM86161 is an ultra-low-power, completely inte- ●● Complete Single-Channel Optical Data Acquisition
grated, optical data-acquisition system. On the transmitter System
side, the MAXM86161 has three programmable high- ●● Built-In Algorithm Further Enhances Rejection of Fast
current LED drivers. On the receiver side, MAXM86161 Ambient Transients
consists of a high efficiency PIN photo-diode and an opti-
cal readout channel. The optical readout has a low-noise ●● Optimized Architecture for Reflective Heart Rate and
signal conditioning analog front-end (AFE), including SpO2 Monitoring
19-bit ADC, an industry-lead ambient light cancellation ●● Low Dark Current Noise of < 50pA RMS (Sample-to-
(ALC) circuit, and a picket fence detect and replace Sample Variance)
algorithm. Due to the low power consumption, compact ●● Lower Effective Dark Current Noise Achievable
size, easy, flexible-to-use, and industry lead ambient light through Multiple Sample Modes and On-Chip
rejection capability of the MAXM86161, the device is ideal Averaging
for a wide variety of optical sensing applications such as
●● High-Resolution 19-bit Charge Integrating ADC
heart rate detection and pulse oximetry.
●● Three Low-Noise 8-Bit LED Current DACs
The MAXM86161 operates on a 3.0V to 5.5V VLED
single supply voltage. It supports a standard compatible ●● Excellent Dynamic Range > 89dB in White Card
interface and fully autonomous operation. Each device Loop-Back Test (Sample-to-Sample Variance)
has a large 128-word built-in FIFO. The MAXM86161 is ●● Excellent Ambient Range and Rejection Capability
available in compact 2.9mm x 4.3mm x 1.4mm, 14-pin • > 100μA Ambient Photodetector Current
OLGA package. • > 70dB Ambient Rejection at 120Hz
●● Ultra-Low-Power Operation for Wearable Devices
Applications
• Low-Power Operation, Optical Readout Channel
●● Optimized for In-Ear Applications < 10μA, Typical at 25sps
●● Miniature Package for Mobile Applications • Short Exposure Integration Period of 14.8μs,
●● Optimized Performance to Detect: 29.4μs, 58.7μs, 117.3μs
• Optical Heart Rate • Low Shutdown Current = 1.6µA (typ)
• Oxygen Saturation (SpO2) ●● Miniature 2.9mm x 4.3mm x 1.4mm, 14-pin OLGA
• Continuous Monitoring for HRV Package
●● -40°C to +85°C Operating Temperature Range

Ordering Information appears at end of data sheet.

19-100523; Rev 0; 3/19

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

TABLE OF CONTENTS
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Benefits and Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Simplified Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Package Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Typical Operating Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Pin Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Detailed Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Optical Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
LED Driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
FIFO Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
LED Sequence Control (0x20 to 0x22) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Pseudo-Code Example of Initialize the Optical AFE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Pseudo-Code for Interrupt Handling with FIFO_A_FULL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Pseudo-Code Example of Reading Data from FIFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Optical Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
One LED Pulsing with No Direct Ambient Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
One LED Pulsing with Direct Ambient Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Two LEDs Pulsing Sequentially with Direct Ambient Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
All LEDs Pulsing Sequentially with Direct Ambient Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
ADC Architecture and Transfer Function Non-Linearity (XNL) Trim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Proximity Mode Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Picket Fence Detect-and-Replace Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Layout Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
I2C/SMBus Compatible Serial Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Detailed I2C Timing Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Bit Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
START and STOP Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Early STOP Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Slave Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Acknowledge Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
I2C Write Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
I2C Read Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

www.maximintegrated.com Maxim Integrated │  2

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

TABLE OF CONTENTS (CONTINUED)

Register Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Register Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
INTERRUPT STATUS 1 (0x00) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
INTERRUPT STATUS 2 (0X01) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
INTERRUPT ENABLE 1 (0X02) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
INTERRUPT ENABLE 2 (0X03) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
FIFO WRITE POINTER (0X04) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
FIFO READ POINTER (0X05) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
OVER FLOW COUNTER (0X06) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
FIFO DATA COUNTER (0X07) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
FIFO DATA REGISTER (0X08) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
FIFO CONFIGURATION 1 (0X09) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
FIFO CONFIGURATION 2 (0X0A) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
SYSTEM CONTROL (0X0D) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
PPG SYNC CONTROL (0X10) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
PPG CONFIGURATION 1 (0X11) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
PPG CONFIGURATION 2 (0X12) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
PPG CONFIGURATION 3 (0X13) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
PROX INTERRUPT THRESHOLD (0X14) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
PHOTO DIODE BIAS (0X15) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
PICKET FENCE (0X16) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
LED SEQUENCE REGISTER 1 (0X20) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
LED SEQUENCE REGISTER 2 (0X21) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
LED SEQUENCE REGISTER 3 (0X22) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
LED1 PA (0x23) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
LED2 PA (0x24) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
LED3_PA (0x25) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
LED PILOT PA (0x29) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
LED RANGE 1 (0X2A) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
S1 HI RES DAC1 (0x2C) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
S2 HI RES DAC1 (0x2D) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
S3 HI RES DAC1 (0x2E) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
S4 HI RES DAC1 (0x2F) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
S5 HI RES DAC1 (0x30) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
S6 HI RES DAC1 (0x31) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
DIE TEMPERATURE CONFIGURATION (0X40) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
DIE TEMPERATURE INTEGER (0X41) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
DIE TEMPERATURE FRACTION (0X42) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

www.maximintegrated.com Maxim Integrated │  3

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

TABLE OF CONTENTS (CONTINUED)

DAC CALIBRATION ENABLE (0X50) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
SHA COMMAND (0XF0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
SHA CONFIGURATION (0XF1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
MEMORY CONTROL (0XF2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
MEMORY INDEX (0XF3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
MEMORY DATA (0XF4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
PART ID (0XFF) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

LIST OF FIGURES
Figure 1. Timing for LED1 Pulsing with No Direct Ambient Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Figure 2. Timing for LED1 Pulsing with Direct Ambient Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Figure 3. Timing for LED1 and LED2 Pulsing Sequentially with Direct Ambient Sampling . . . . . . . . . . . . . . . . . . . . . 23
Figure 4. Timing for LED1, LED2, and LED3 Pulsing Sequentially with Direct Ambient Sampling . . . . . . . . . . . . . . . 24
Figure 5. Proximity Function Flow Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Figure 6. Picket Fence Function Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Figure 7. Picket Fences Variables In A PPG Waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Figure 8. Layout Guideline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Figure 9. Detailed I2C Timing Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Figure 10. I2C START, STOP, and REPEATED START Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Figure 11. I2C Acknowledge Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Figure 12. I2C Single Byte Write Transaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Figure 13. I2C Multi-Byte Write Transaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Figure 14. I2C Single Byte Read Transaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Figure 15. I2C Multibyte Read Transaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

LIST OF TABLES
Table 1. LED Sequence Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Table 2. LED Sequence Register Data Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Table 3. FIFO Data, Tag and Sample Counter Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Table 4. FIFO configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 5. Optical FIFO Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Table 6. Slave Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

www.maximintegrated.com Maxim Integrated │  4

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Simplified Block Diagram

VLDO
VREF REFERENCE MAXM86161 LDO_EN

DIGITAL NOISE
AMBIENT CANCELLATION INTB
CANCELLATION
SDA
I2C SCL
128 FIFO
PD INTERFACE GPIO
19-BIT CURRENT ADC

VLED
IR RED GRN

N.C.
N.C. LED DRIVER CONTROLLER
N.C.

PGND GND_ANA
GND_DIG

www.maximintegrated.com Maxim Integrated │  5

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Absolute Maximum Ratings

VLDO to GND_ANA..............................................-0.3V to +2.2V Output Short-Circuit Duration.....................................Continuous
VLDO to GND_DIG...............................................-0.3V to +2.2V Continuous Input Current Into Any Pin
GND_DIG to GND_ANA........................................-0.3V to +0.3V (except LED_DRVx Pins)..............................................±20mA
PGND to GND_ANA..............................................-0.3V to +0.3V Continuous Power Dissipation
SCL, SDA, INTB, GPIO to GND_ANA..................-0.3V to +6.0V (OLGA; Derate 5.5mW/°C above +70°C).......................36mW
LDO_EN to GND_DIG..........................................-0.3V to +6.0V Operating Temperature Range............................ -40°C to +85°C
VLED to PGND......................................................-0.3V to +6.0V Storage Temperature Range............................. -40°C to +105°C
Soldering Temperature (reflow)........................................+260°C

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.

Package Information
PACKAGE TYPE: 14-PIN OLGA
Package Code F142A4+1
Outline Number 21-100309
Land Pattern Number 90-100106
THERMAL RESISTANCE, FOUR-LAYER BOARD:
Junction to Ambient (θJA) 55.49°C/W
Junction to Case (θJC) N/A

For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.

Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer board.
For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.

Electrical Characteristics
(VLED = 5.0V, PPG1_ADC_RGE = 16μA, PPG_SR = 512sps, PPG_TINT = 117.3μs, LED_SETLNG = 6μs, LEDx_RGE = 31mA,
PDBIAS1 = 0x1, TA = 25°C, min/max are from TA = -40°C to +85°C, unless otherwise noted.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
POWER SUPPLY
LED Supply Voltage
VLED Verified during PSRR Test 3.0 5.5 V
(Note 2)
LDO Output Voltage VLDO 1.68 1.8 1.92 V
LEDx_PA = 0x00,
PPG_TINT = Three LED Exposures/
400 600
117.3µs, PPG_SR Sample
Average LED Supply = 100sps
ILED μA
Current LEDx_PA = 0xFF, One LED Exposure/Sample 600
PPG_TINT = Two LED Exposure/Sample 970
117.3µs, PPG_SR
= 100sps Three LED Exposure/Sample 1300

LED Supply Current in LDO_EN = 1, SHDN = 1 1.6 11

ILEDSHDN μA
Shutdown LDO_EN = 0 0.05 0.3
VREF 1.195 1.210 1.220 V

www.maximintegrated.com Maxim Integrated │  6

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Electrical Characteristics (continued)

(VLED = 5.0V, PPG1_ADC_RGE = 16μA, PPG_SR = 512sps, PPG_TINT = 117.3μs, LED_SETLNG = 6μs, LEDx_RGE = 31mA,
PDBIAS1 = 0x1, TA = 25°C, min/max are from TA = -40°C to +85°C, unless otherwise noted.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
READOUT CHANNEL
ADC Resolution 19 bits
Propriety ATE
setup, PPG_TINT PPG1_ADC_RGE = 32μA,
IR ADC Count IRC = 117.3µs, PPG_ LED2_RGE = 124mA -15% 155000 +15% Counts
SR = 512sps, TA = LED2_PA = 0xFF
+25°C
Propriety ATE
setup, PPG_TINT PPG1_ADC_RGE = 16μA,
Green ADC Count GREENC = 117.3µs, PPG_ LED1_RGE = 124mA -15% 135000 +15% Counts
SR = 512sps, TA = LED1_PA = 0xFF
+25°C
Propriety ATE
setup, PPG_TINT PPG1_ADC_RGE = 32μA
Red ADC Count REDC = 117.3µs, PPG_ LED3_RGE = 124mA -15% 200000 +15% Counts
SR = 512sps, TA = LED3_PA = 0xFF
+25°C
Bench test setup,
PPG_TINT = PPG1_ADC_RGE = 32μA,
IR ADC Noise IRSTD 117.3µs, PPG_SR LED2_RGE = 124mA 7 Counts
= 128sps, TA = LED2_PA = 0xFF
+25°C
Bench test setup,
PPG_TINT = PPG1_ADC_RGE = 16μA,
Green ADC Noise GREENSTD 117.3µs, PPG_SR LED1_RGE = 124mA 7 Counts
= 128sps, TA = LED1_PA = 0xFF
+25°C
Bench test setup,
PPG_TINT = PPG1_ADC_RGE1 = 32μA,
Red ADC Noise REDSTD 117.3µs, PPG_SR LED3_RGE = 124mA 8.9 Counts
= 128sps, TA = LED3_PA = 0xFF
+25°C
PPG1_ADC_RGE = 0x0 4.0
ADC Full Scale Input PPG1_ADC_RGE = 0x1 8.0
μA
Current PPG1_ADC_RGE = 0x2 16.0
PPG1_ADC_RGE = 0x3 32.0
PPG_TINT = 0x0 14.8
PPG_TINT = 0x1 29.4
ADC Integration Time tINT μs
PPG_TINT = 0x2 58.7
PPG_TINT = 0x3 117.3
Minimum PPG Sample
PPG_SR = 0x0A 8 sps
Rate

www.maximintegrated.com Maxim Integrated │  7

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Electrical Characteristics (continued)

(VLED = 5.0V, PPG1_ADC_RGE = 16μA, PPG_SR = 512sps, PPG_TINT = 117.3μs, LED_SETLNG = 6μs, LEDx_RGE = 31mA,
PDBIAS1 = 0x1, TA = 25°C, min/max are from TA = -40°C to +85°C, unless otherwise noted.) (Note 1)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Maximum PPG Sample
PPG_SR = 0x13 4096 sps
Rate
Sample Rate Error From nominal as indicated in the PPG_SR table -2 +2 %
LEDx_PA = 0x00, PPG_TINT = 117.8μs,
1 20 Counts
PPG_SR = 100sps, PPG1_ADC_RGE = 4μA
Dark Current Count LED_DCC
LEDx_PA = 0x00, PPG_TINT = 117.8μs,
0.001 0.004 % of FS
PPG_SR = 100sps, PPG1_ADC_RGE = 4μA
Maximum DC Ambient
ALR TA = +25°C 200 μA
Light Rejection
LEDx_PA = 0x00, PPG_TINT = 117.8µs,
Ambient Light Detect
ADD_OFFSET = 0x1, PPG_SR = 100sps, 5 25 Counts
Noise
PPG1_ADC_RGE = 4µA, TA = +25°C.
For IR
Propriety ATE 0.05 1
3V < VLED+ < 5.5V
setup, LEDx_RGE
For Red
= 124mA, LEDx_ 0.05 1 % of FS
4V < VLED+ < 5.5V
PA = 0xFF, TA =
ADC Count - PSRR +25°C to +85°C For Green
PSRRVLED 0.05 1
(VLED) (Note 2) 4.8V < VLED+ < 5.5V
LEDx_RGE =
124mA, Frequency = DC to 100kHz,
40 LSB
PPG_TINT = 100mVP-P
120μs
LED DRIVER
LED Current Resolution 8 Bits
LEDx_RGE = 0x0 31
Full Scale LED Current LEDx_RGE = 0x1 62
ILED LEDx_PA = 0xFF mA
(Note 3) LEDx_RGE = 0x2 93
LEDx_RGE = 0x3 124
LEDx_RGE = 0x0 160 253
LEDx_PA = 0xFF,
95% of the LEDx_RGE = 0x1 317
Minimum Output Voltage VOL mV
desired LED LEDx_RGE = 0x2 495
current
LEDx_RGE = 0x3 700
LED1 Driver Compliance
LED1COMP 180 mV
Interrupt
IR LED CHARACTERISTICS (NOTE 4)
Centroid Wavelength λcentroid IF = 100mA, tp = 10ms, TA = +25°C 880 nm
Forward Voltage VF IF = 100mA, tp = 10ms, TA = +25°C 1.6 1.9 V
Radiant Power Φe IF = 100mA, TA = +25°C 38 mW
Maximum Junction Tem-
TJ 115 °C
perature

www.maximintegrated.com Maxim Integrated │  8

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Electrical Characteristics (continued)

(VLED = 5.0V, PPG1_ADC_RGE = 16μA, PPG_SR = 512sps, PPG_TINT = 117.3μs, LED_SETLNG = 6μs, LEDx_RGE = 31mA,
PDBIAS1 = 0x1, TA = 25°C, min/max are from TA = -40°C to +85°C, unless otherwise noted.) (Note 1)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

RED LED CHARACTERISTICS (NOTE 4)
Centroid Wavelength λcentroid IF = 20mA, TA = +25°C 660 nm
Forward Voltage VF IF = 20mA, tp =5ms, TA = +25°C 2.1 2.5 V
Radiant Power Φe IF = 20mA, TA = +25°C 9 mW
Maximum Junction Tem-
TJ 115 °C
perature
GREEN LED CHARACTERISTICS (NOTE 4)
Centroid Wavelength λcentroid IF = 150mA, tp = 10ms, TA = +25°C 520 535 nm
Forward Voltage VF IF = 150mA, tp = 5ms, TA = +25°C 3.0 3.35 3.8 V
Radiant Power Φe IF = 150mA, TA = +25°C 25 mW
Maximum junction tem-
TJ 150 °C
perature
PHOTODIODE (NOTE 4)
Wavelength of Peak
860 nm
Sensitivity
Spectral Bandwidth 420 to
nm
Range 1020
DIGITAL I/O CHARACTERISTICS (SDA, SCL, INTB, GPIO, LDO_EN)
Open Drain Output Low
VOL_OD SDA, INTB, GPIO, ISINK = 6mA 0.4 V
Voltage
SDA and SCL 0.4
Input Voltage Low VIL V
LDO_EN 0.3
SDA and SCL 1.4
Input Voltage High VIH V
LDO_EN 1.1
Input Hysteresis VHYS SDA and SCL 400 mV
VIN = 0V, TA = +25°C 0.01 1
Input Leakage Current IIN μA
VIN = 5.5V, TA = +25°C 0.01 1
Input Capacitance CIN 10 pF
I2C TIMING CHARACTERISTICS (NOTE 5)
I2C Write Address C4 Hex
I2C Read Address C5 Hex
Serial Clock Frequency fSCL 0 400 kHz
Bus Free Time Between
STOP and START Con- tBUF 1.3 µs
ditions
Hold Time START and
Repeat START Condi- tHD_STA 0.6 µs
tion
SCL Pulse-Width Low tLOW 1.3 µs

www.maximintegrated.com Maxim Integrated │  9

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Electrical Characteristics (continued)

(VLED = 5.0V, PPG1_ADC_RGE = 16μA, PPG_SR = 512sps, PPG_TINT = 117.3μs, LED_SETLNG = 6μs, LEDx_RGE = 31mA,
PDBIAS1 = 0x1, TA = 25°C, min/max are from TA = -40°C to +85°C, unless otherwise noted.) (Note 1)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

SCL Pulse-Width High tHIGH 0.6 µs
Setup Time for a Re-
tSU_STA 0.6 µs
peated START Condition
Data Hold Time tHD_DAT 0 900 ns
Data Setup Time tSU_DAT 100 ns
Setup Time for STOP
tSU_STO 0.6 µs
Condition
Pulse Width of Sup-
tSP 0 50 ns
pressed Spike
Bus Capacitance CB 400 pF
SDA and SCL Receiving 20 +
tR 300 ns
Rise Time 0.1CB
SDA and SCL Receiving 20 +
tF 300 ns
Fall Time 0.1CB
SDA Transmitting Fall 20 +
tTF 300 ns
Time 0.1CB
GPIO External Sync Low GPIO_CTRL = 10 5 μs
tPLGPIO
Pulse Width GPIO_CTRL = 2 64 μs

Note 1: All devices are 100% production tested at TA = +25°C. Specifications over temperature limits are guaranteed by
MaximIntegrated’s bench or proprietary automated test equipment (ATE) characterization.
Note 2: VLED should be set to accommodate the maximum LED forward voltage and the output compliance of the LED driver.
Note 3: The LED current is trim in production to meet the IR, GREEN, and RED ADC counts. Actual values can vary by up to ±50%.
Values shown here are for 0% trim.
Note 4: For design guidance only. Not production tested. Tested in die form only.
Note 5: For design guidance only. Not production tested.

www.maximintegrated.com Maxim Integrated │  10

 MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Typical Operating Characteristics

(VLED = 5.0V, GND = PGND = 0V, TA = +25°C, unless otherwise noted)

LED1 - 530nm LED2 - 880nm LED3 - 660nm

SIGNAL-TO-NOISE RATIO vs. ADC INPUT CURRENT SIGNAL-TO-NOISE RATIO vs. ADC INPUT CURRENT SIGNAL-TO-NOISE RATIO vs. ADC INPUT CURRENT
PPG1_ADC_RGE = 32µA PPG1_ADC_RGE = 32µA PPG1_ADC_RGE = 32µA
toc01 toc03 toc02
90 90 90
117.3µs 117.3µs
117.3µs
85 85 85
58.7µs 58.7µs
58.7µs

SIGNAL-TO-NOISE RATIO (dB)

SIGNAL-TO-NOISE RATIO (dB)

SIGNAL-TO-NOISE RATIO (dB)

80 80 80
29.4µs 29.4µs 29.4µs
75 75 75
14.8µs 14.8µs 14.8µs
70 70 70

65 65 65

60 60 60

55 55 55

50 50 50

45 45 45
0.1 1 10 0.1 1 10 0.1 1 10
ADC INPUT CURRENT (µA) ADC INPUT CURRENT (µA) ADC INPUT CURRENT (µA)

LED 2D - RADIATION PATTERN LED 2D - RADIATION PATTERN PHOTODIODE FIELD OF VIEW

HORIZONTAL VERTICAL HORIZONTAL AND VERTICAL
toc04 toc05
1.2 1.2 1.2
toc06

LED 3 - 660nm
LED 1 - 530nm VERTICAL HORIZONTAL
1.0 1.0 1.0
LED 2 - 880nm
RELATIVE INCIDENT POWER

LED 1 - 530nm
RELATIVE INTENSITY
RELATIVE INTENSITY

0.8 0.8 0.8

0.6 0.6 0.6

0.4 0.4 0.4

LED 2 -
0.2 880nm 0.2 0.2

LED 3 - 660nm
0.0 0.0 0.0
-90 -70 -50 -30 -10 10 30 50 70 90 -90 -70 -50 -30 -10 10 30 50 70 90 -90 -70 -50 -30 -10 10 30 50 70 90
RADIATION ANGLE (º) RADIATION ANGLE (º) ROTATION ANGLE (º)

PHOTODIODE RELATIVE
SPECTRAL RESPONSIVITY PHOTODIODE DARK CURRENT
toc07 toc08
1.2 600
RELATIVE SPECTRAL RESPONSIVITY

1.0 500 ADC_8µA

DARK CURRENT (pA)

0.8 400
ADC_4µA

0.6 300

0.4 200
ADC_16µA ADC_32µA
0.2 100

0.0 0
400 600 800 1000 10 30 50 70 90 110
WAVELENGTH (nm) INTEGRATION TIME (µs)

www.maximintegrated.com Maxim Integrated │  11

 MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Typical Operating Characteristics (continued)

(VLED = 5.0V, GND = PGND = 0V, TA = +25°C, unless otherwise noted)

LED-PHOTODIODE CROSSTALK AMBIENT LIGHT REJECTION

AT 124mA AMBIENT REJECTION vs. FREQUENCY EXPOSURE SHIFT vs. AMBIENT INPUT
toc09 toc10 toc11
120 0 4.0
LED 3 - 660nm 117.3µs 117.3µs
-10 3.5 LED SETTLING = 6µs
100
PHOTODIODE CURRENT (nA)

AMBIENT REJECTION (dB)

-20 3.0

EXPOSURE SHIFT (nA)

80
LED 2 - 880nm -30 2.5
14.8µs
60 -40 2.0

-50 1.5
40 117.3µs
-60 1.0 LED SETTLING = 12µs
LED 1 - 530nm
20
-70 0.5

0 -80 0.0
10 30 50 70 90 110 10 100 1000 10000 0 1 10 100
INTEGRATION TIME (µs) FREQUENCY OF AMBIENT(Hz) INPUT CURRENT DUE TO AMBIENT (µA)

LED LINEARITY AFE POWER DISSIPATION SYSTEM POWER DISSIPATION WITH 1 LED
RELATIVE LUMINOUS INTENSITY LP_BOOST = 1, GPIO MODE = 0 LP_BOOST = 1, LEDx_PA = 124mA
toc12 toc13 toc14
1.1 900 18
117.3µs 117.3µs
1 800 16
0.9 LED 3 - 700 14
0.8 660nm
NORMALIZED AT 125mA

58.7µs
600 12
0.7
POWER (mW)
POWER (µW)

LED 1 - 500 29.4µs 10

0.6 58.7µs
530nm
0.5 400 8
14.8µs
LED 2 -
0.4
880nm 300 6 29.4µs
0.3
200 4
0.2
0.1 100 2 14.8µs

0 0 0
0 20 40 60 80 100 120 0 100 200 300 0 100 200 300
DC FORWARD CURRENT (mA) SAMPLING RATE (Hz) SAMPLING RATE (Hz)

VLED DC PSRR VLED AC PSRR

PD CURRENT = 31µA PD CURRENT = 31µA
toc 15
0.10 toc16
200
0.09 180 14.8µs
0.08
PEAK-TO-PEAK COUNTS/50mV

160
ABSOLUTE % CHANGE/V

0.07 140 29.4µs

0.06 120
0.05 100
0.04 80 58.7µs
0.03 60
0.02 40
117.3µs
0.01 20
0.00 0
14.6 29.2 58.6 117.1 0.1 10 1000 100000 10000000
TINT (µs) SAMPLING RATE (Hz)

www.maximintegrated.com Maxim Integrated │  12

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Pin Configuration

SDA 1 14 INTB

SCL 2 13 GPIO

LDO_EN 3 12 VREF
MAXM86161

VLDO 4 11 GND_ANA

VLED 5 10 GND_DIG

N.C. 6 9 PGND

N.C. 7 8 N.C.

Pin Description
PIN NAME FUNCTION
POWER
5 VLED LED Power Supply Input. Connect to external voltage supply. Bypass with a 10μF capacitor to PGND.
9 PGND LED Power Return. Connect to GND.
10 GND_DIG Digital Logic and Digital Pad Return. Connect to GND_ANA.
11 GND_ANA Analog Power Return. Connect to GND.
CONTROL INTERFACE
1 SDA SDA Input/Output. Input/output for I2C data.
2 SCL SCL Input. I2C clock.
LDO Enable Input. Pull HIGH to turn on the internal LDO. Pull LOW to turn off the internal LDO. When
3 LDO_EN
pulled LOW, part in shut down.
13 GPIO General Purpose Input/Output. Open-drain when programmed as output (active-low).
14 INTB Open Drain Interrupt.
REFERENCE
4 VLDO Internal LDO output. Bypass with a 1μF capacitor to GND_ANA.
12 VREF Internal Reference Decoupling Point. Bypass with a 1µF capacitor to GND_ANA.
LED DRIVER
6
7 N.C. No Connection. Internally connected to LEDx, Solder to PCB for mechanical stability.
8

www.maximintegrated.com Maxim Integrated │  13

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Detailed Description and changing residual ambient light from the sensor
The MAXM86161 is a complete, integrated, optical data measurements.
acquisition system, ideal for optical pulse oximetry and The MAXM86161 supports dynamic power down mode
heart-rate detection applications. It has been designed (low power mode) in which the power consumption is
for the demanding requirements of mobile and wearable decreased between samples. This mode is only support-
devices, requiring minimal external hardware components ed for sample rates 256sps and below. For more details
to be integrated into a wearable device. The MAXM86161 on the power consumption at each sample rate, please
includes high-resolution optical readout signal process- refer to the Electrical Characteristics table.
ing channels with robust ambient light cancellation and
high-current LED driver DACs to form a complete optical
LED Driver
readout signal chain. The MAXM86161 integrates three precision LED driver
current DACs that modulate LED pulses for a variety of
The module is fully adjustable through software registers
optical measurements. The LED current DACs have 8 bits
and the digital output data is stored in a 128-word FIFO
of dynamic range with four programmable full-scale rang-
within the IC. The FIFO allows the MAXM86161 to be
es of 31mA, 62mA, 94mA, and 124mA. The LED drivers
connected to a microcontroller or processor on a shared
are low dropout current sources allowing for low-noise,
bus where the data is not being read continuously from
power-supply independent LED currents to be sourced at
the MAXM86161 registers. It operates in fully autono-
the lowest supply voltage possible, minimizing LED power
mous modes for low-power battery applications.
consumption. The LED pulse width can be programmed
The MAXM86161 consists of a single optical readout from 14.8μs to 117.3μs to allow the algorithms to optimize
channel. MAXM86161 has three LED drivers and is well SpO2 and HR accuracy at the lowest dynamic power con-
suited for a wide variety of optical sensing applications. sumption dictated by the application.
The module operates on a 3.0V to 5.5V VLED single
FIFO Configuration
supply voltage. It has flexible timing and shutdown con-
figurations as well as control of individual blocks so an The FIFO has 128 sample depth and is designed to sup-
optimized measurement can be made at minimum power port various data types, as shown in Table 2. Each sample
levels. width is 3 bytes, which includes a 5-bit tag width. The
tag embedded in the FIFO_DATA is used to identify the
Optical Subsystem source of each sample data. The description of each tag
The optical subsystem in MAXM86161 is composed is as shown in Table 3.
of ambient light cancellation (ALC), a continuous-time Index to the data within a sample identifies the input
sigma-delta ADC, and proprietary discrete time filter. ALC to the PPG channels, and follows the order in the LED
incorporates a proprietary scheme to cancel ambient- Sequence Control registers (Table 1).
light-generated photo diode currents, allowing the sensor
to work in high ambient light conditions. The optical ADC LED Sequence Control (0x20 to 0x22)
has programmable full-scale ranges of 4μA to 32μA. The The data format in the FIFO as well as the sequenc-
internal ADC is a continuous time, oversampling sigma- ing of exposures are controlled by the LED Sequence
delta converter with 19-bit resolution. The ADC output Registers using LEDC1 through LEDC6. There are six LED
data rate can be programmed from 8sps (samples per Sequence Data Types available as shown in Table 2. The
second) to 4096sps. The MAXM86161 includes a propri- exposure sequence cycles through the LED Sequence
etary discrete time filter to reject 50Hz/60Hz interference bit fields starting from LEDC1 to LEDC6. The first LED
Sequence field set to NONE (0000) ends the sequence.

Table 1. LED Sequence Control Registers

ADDRESS REGISTER NAME DEFAULT VALUE B7 B6 B5 B4 B3 B2 B1 B0
0x20 LED Sequence Register 1 00 LEDC2[3:0] LEDC1[3:0]
0x21 LED Sequence Register 2 00 LEDC4[3:0] LEDC3[3:0]
0x22 LED Sequence Register 3 00 LEDC6[3:0] LEDC5[3:0]

www.maximintegrated.com Maxim Integrated │  14

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Table 2 lists the codes for exposures selected in the LED There are seven registers that control how the FIFO is
Sequence Control Registers. configured and read out. These registers are illustrated
Table 3 shows the format of the FIFO data along with in Table 4.
the associated tag. In a sample, if a picket fence event is
detected, the predicted value is pushed to the FIFO along
with its tag (PPFx_LEDCx_DATA).

Table 2. LED Sequence Register Data Type

LEDCN[3:0]; (N = 1 – 6) DATA TYPE
0000 NONE
0001 LED1
0010 LED2
0011 LED3
0100 Reserved
0101 Reserved
0110 Reserved
0111 Reserved
1000 Pilot on LED1
1001 DIRECT AMBIENT
1010 Reserved
1011 Reserved
1100 Reserved
1101 Reserved
1110 Reserved
1111 Reserved

Table 3. FIFO Data, Tag and Sample Counter Format

FIFO_DATA[23:19]; FIFO_DATA[18:0];
COMMENTS
TAG] DATA TYPE
00001 PPG1_LEDC1_DATA If LEDC1 is nonzero
00010 PPG1_LEDC2_DATA If LEDC1 and LEDC2 are nonzero
00011 PPG1_LEDC3_DATA If LEDC1, LEDC2, and LEDC3 are nonzero
00100 PPG1_LEDC4_DATA If LEDC1, LEDC2, LEDC3, and LEDC4 are nonzero
00101 PPG1_LEDC5_DATA If LEDC1, LEDC2, LEDC3, LEDC4, and LEDC5 are nonzero
00110 PPG1_LEDC6_DATA If LEDC1, LEDC2, LEDC3, LEDC4, LEDC5, and LEDC6 are nonzero
00111 PPG2_LEDC1_DATA PPG2 not available
01000 PPG2_LEDC2_DATA PPG2 not available
01001 PPG2_LEDC3_DATA PPG2 not available
01010 PPG2_LEDC4_DATA PPG2 not available
01011 PPG2_LEDC5_DATA PPG2 not available
01100 PPG2_LEDC6_DATA PPG2 not available

www.maximintegrated.com Maxim Integrated │  15

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Table 3. FIFO Data, Tag and Sample Counter Format (continued)

FIFO_DATA[23:19]; FIFO_DATA[18:0];
COMMENTS
TAG] DATA TYPE
01101 PPF1_LEDC1_DATA If LEDC1 is nonzero (Picket Fence event)
01110 PPF1_LEDC2_DATA If LEDC1 and LEDC2 are nonzero (Picket Fence event)
01111 PPF1_LEDC3_DATA If LEDC1, LEDC2, and LEDC3 are nonzero (Picket Fence event)
10000 Reserved
10001 Reserved
10010 Reserved
10011 PPF2_LEDC1_DATA PPG2 not available
10100 PPF2_LEDC2_DATA PPG2 not available
10101 PPF2_LEDC3_DATA PPG2 not available
10110 Reserved
10111 Reserved
11000 Reserved
11001 PROX1_DATA Only PILOT LED1 for LEDC1 is used
11010 PROX2_DATA PPG2 not available
11011 Reserved
11100 Reserved
11101 Sub-DAC Update This tag indicates that the sub-DAC had updated on this conversion
11110 INVALID_DATA This tag indicates that there was an attempt to read an empty FIFO
11111 TIME_STAMP If TIME_STAMP_EN = 1, this is TIME_STAMP

Table 4. FIFO configuration

REGISTER DEFAULT
ADDRESS B7 B6 B5 B4 B3 B2 B1 B0
NAME VALUE
FIFO Write
0X04 00 — FIFO_WR_PTR[6:0]
Pointer
FIFO Read
0X05 00 — FIFO_RD_PTR[6:0]
Pointer
Overflow
0X06 00 — OVF_COUNTER[6:0]
Counter
FIFO Data
0X07 00 FIFO_DATA_COUNT[7:0]
Counter
FIFO Data
0X08 00 FIFO_DATA[7:0]
Register
FIFO
0X09 00 — FIFO_A_FULL[6:0]
Configuration 1
FIFO TIME_ FLUSH_ FIFO_ A_FULL_
0X0A 00 — — FIFO_RO -
Configuration 2 STAMP_EN FIFO STAT_CLR TYPE

www.maximintegrated.com Maxim Integrated │  16

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Write Pointer (register 0X04) FIFO Data (register 0X08)

FIFO_WR_PTR[6:0] points to the FIFO location where the FIFO_DATA[7:0] is a read-only register used to retrieve
next item is written. This pointer advances for each item data from the FIFO. It is important to burst read the item
pushed on to the FIFO by the internal conversion process. from the FIFO. Each item is three bytes. So burst read-
The write pointer is a 7-bit counter and wraps around to ing three bytes at FIFO_DATA register using the serial
count 0x00 on the next item after count 0x7F. interface advances the FIFO_RD_PTR. The format and
Read Pointer (register 0X05) data type of the data stored in the FIFO is determined by
the tag associated with the data. The readout from the
FIFO_RD_PTR[6:0] points to the location from where the FIFO follows a progression defined by the LED Sequence
next item from the FIFO is read using the serial interface. Control registers as well. This configuration is best illus-
This advances each time an item is read from the FIFO. trated by a few examples.
The read pointer can be both read and written to. This
allows an item to be reread from the FIFO if it has not Assume it is desired to perform an SpO2 measurement
already been overwritten. The read pointer is updated and also monitor the ambient level on the photodiode to
from a 7-bit counter and wraps around to count 0x00 from adjust the IR and red LED intensity. To perform this mea-
count 0x7F. surement, configure the following registers.
Overflow Counter (register 0X06) LED SEQUENCE CONTROL
OVF_COUNTER[6:0] logs the number of items lost if the LEDC1 = 0x2 LED2 exposure
FIFO is not read in a timely fashion. This counter holds/ LEDC2 = 0x3 LED3 exposure
saturates at count value 0x7F. When a complete item is LEDC3 = 0x9 DIRECT AMBIENT exposure
popped from the FIFO (when the read pointer advances),
LEDC4 = 0x0 NONE
the OVF_COUNTER is reset to zero. This counter is
essentially a debug tool. It should be read immediately LEDC5 = 0x0 NONE
before reading the FIFO in order to check if an overflow LEDC6 = 0x0 NONE
condition has occurred. PPG CONFIGURATION
FIFO Data Counter (register 0x07) PPG1_ADC_RGE[1:0] PPG1 Gain Range Control
FIFO_DATA_COUNT[7:0] is a read-only register which PPG_TINT[1:0] LED Pulse Width Control
holds the number of items available in the FIFO for the PPG_SR[3:0] Sample Rate
host to read. This increments when a new item is pushed
LED PULSE AMPLITUDE
to the FIFO and decrements when the host reads an item
from the FIFO. LED2_PA[7:0] LED2 Drive Current
LED3_PA[7:0] LED3 Drive Current

www.maximintegrated.com Maxim Integrated │  17

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

When done so the sample sequence and the data format in the FIFO follows the following time/location sequence.
tag 1, PPG1 LED2 data
tag 2, PPG1 LED3 data
tag 3, PPG1 Ambient data
tag 1, PPG1 LED2 data
tag 2, PPG1 LED3 data
tag 3, PPG1 Ambient data
.
.
.
tag 1, PPG1 LED2 data
tag 2, PPG1 LED3 data
tag 3, PPG1 Ambient data

where,
PPGm LED1 data = Ambient corrected exposure data from LED1 in PPGm channel,
PPGm LED2 data = Ambient corrected exposure data from LED2 in PPGm channel
PPGm Ambient data = Direct ambient sample in PPGm channel
m = 1 of PPG1 channel
To calculate the number of available items when the INT signal is seen, one can perform the following pseudo-code:
read the OVF_COUNTER register
read the FIFO_DATA_COUNT register
if OVF_COUNTER == 0 //no overflow occurred
NUM_AVAILABLE_SAMPLES = FIFO_DATA_COUNT
else
NUM_AVAILABLE_SAMPLES = 128 // overflow occurred and data has been lost
endif

www.maximintegrated.com Maxim Integrated │  18

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Table 6 shows the FIFO data format depends on the A_FULL_TYPE (0x0A)
data type being stored. Optical data, whether full ambient The A_FIFO_TYPE bit defines the behavior of the A_
corrected LED exposure, ambient corrected proximity or FULL interrupt. If the A_FIFO_TYPE bit is set low, the
direct ambient sampled data is left-justified, as shown in A_FULL interrupt gets asserted when the A_FULL con-
Table 5. Bits F23:F19 of the FIFO word contains the tag dition is detected and cleared by status register read,
that identifies the data. but reasserts for every sample if the A_FULL condition
FIFO_A_FULL (0x09) persists. If the A_FIFO_TYPE bit is set high, the A_FULL
The FIFO_A_FULL[6:0] field in the FIFO Configuration interrupt gets asserted only when a new A_FULL condi-
1 register (0x09) sets the watermark for the FIFO and tion is detected. The interrupt gets cleared on the Interrupt
determines when the A_FULL bit in the Interrupt_Status Status 1 register read, and does not reassert for every
register (0x00) gets asserted. The A_FULL bit is set when sample until a new A_FULL condition is detected.
the FIFO contains 128 minus FIFO_A_FULL[6:0] items. FIFO_STAT_CLR (0x0A)
When the FIFO is almost full, if the A_FULL_EN mask The FIFO_STAT_CLR bit defines whether the A-FULL
bit in the Interrupt_Enable register (0x03) is set, then interrupt should get cleared by the FIFO_DATA register
A_FULL bit gets asserted in the Interrupt Status 1 register read. If FIFO_STAT_CLR is set low, A_FULL and DATA_
and this bit is routed to the INT pin on the serial interface. RDY interrupts do not get cleared by the FIFO_DATA
This condition should prompt the applications processor register read but get cleared by the status register read.
to read samples off of the FIFO before it fills. The A_FULL If FIFO_STAT_CLR is set high, the A_FULL and DATA_
bit is cleared when the status register is read. RDY interrupts get cleared by a FIFO_DATA register read
The application processor can read both the FIFO_WR_ or a status register read.
PTR and FIFO_RD_PTR to calculate the number of items FLUSH_FIFO (0x0A)
available in the FIFO, or just read the OVF_COUNTER
and FIFO_DATA_COUNT registers, and read as many The FIFO Flush bit is used for flushing the FIFO. The
items as it needs to empty the FIFO. Alternatively, if FIFO becomes empty and the FIFO_WR_PTR[6:0],
the applications always responds much faster than FIFO_RD_PTR[6:0], FIFO_DATA_COUNT[7:0] and
the selected sample rate, it could just read 128 minus OVF_COUNTER[6:0] get reset to zero. FLUSH_FIFO is
FIFO_A_FULL[6:0] items when it gets A_FULL interrupt a self-clearing bit.
and be assured that all data from the FIFO are read.​ TIME_STAMP_EN (0x0A)
FIFO_RO (0x0A) When the TIME_STAMP_EN bit is set to 1, the 19 bits
The FIFO_RO bit in the FIFO Configuration 2 register time stamp gets pushed to the FIFO along with its tag for
(0x0A) determines whether samples get pushed on to every 8 samples. This time stamp is useful for aligning
the FIFO when it is full. If push is enabled when FIFO is data from two devices after the host reads the FIFOs of
full, old samples are lost. If FIFO_RO is not set, the new those devices. When the TIME_STAMP_EN bit is set to 0,
sample is dropped and the FIFO is not updated. the sample counter is not pushed to FIFO.

Table 5. Optical FIFO Data Format

FIFO DATA FORMAT (FIFO_DATA[23:0])
TAG (TAG[4:0]) ADC VALUE (FIFO_DATA[18:0])
F23 F22 F21 F20 F19 F18 F17 F16 F15 F14 F13 F12 F11 F10 F9 F8 F7 F6 F5 F4 F3 F2 F1 F0
T4 T3 T2 T1 T0 O18 O17 O16 O15 O14 O13 O12 O11 O10 O9 O8 O7 O6 O5 O4 O3 O2 O1 O0

Table 6. Slave Address

WRITE READ
I2C Slave Address 0xC4 0xC5

www.maximintegrated.com Maxim Integrated │  19

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Pseudo-Code Example of Initialize the Optical AFE

The following pseudo-code shows an example of configuring MAXM86161 for an SpO2 applications, where LED2 and
LED3 are IR and red LED, respectively.
DEVICE OPEN
START;
// AFE Initialization
WRITE RESET[0] to 0x1; // Soft Reset (Register 0x0D[0])
DELAY 1ms;
WRITE SHDN[0] to 0x1; // Shutdown (Register 0x0D[1])
READ Interrupt_Status_1; // Clear Interrupt (Register 0x00)
READ Interrupt_Status_2; // Clear Interrupt (Register 0x01)
WRITE PPG_TINT[1:0] to 0x3; // Pulse Width = 123.8ms (Register 0x11[1:0])
WRITE PPG1_PPG1_ADC_RGE1:0] to 0x2; // ADC Range = 16μA (Register 0x11[3:2])

WRITE SMP_AVE[2:0] to 0x0; // Sample Averaging = 1 (Register 0x12[2:0])

WRITE PPG_SR[4:0] to 0x00; // Sample Rate = 25sps (Register 0x12[7:3])
WRITE LED_SETLNG[1:0] to 0x3; // LED Settling Time = 12ms (Register 0x13[7:6])
WRITE PDBIAS11[2:0] to 0x01; // PD 1 Biasing for Cpd = 0~65pF (Register 0x15[2:0])

WRITE LED1_RGE[1:0] to 0x3; // LED Driver 1 Range = 124mA (Register 0x15[2:0])

WRITE LED2_RGE[1:0] to 0x3; // LED Driver 2 Range = 124mA (Register 0x15[2:0])
WRITE LED1_DRV[1:0] to 0x20; // LED 1 Drive Current = 15.36mA (Register 0x23[7:0])
WRITE LED2_DRV[1:0] to 0x20; // LED 2 Drive Current = 15.36mA (Register 0x24[7:0])
WRITE LP_Mode[0] to 0x1; // Low Power mode enabled
// FIFO Configuration
WRITE FIFO_A_FULL[6:0] to 0xF; // FIFO INT triggered condition (Register 0x09[6:0])
WRITE FIFO_RO to 0x1; // FIFO Roll Over enabled (Register 0x0A[1])
WRITE A_FULL_EN to 0x1; // FIFO_A_FULL interrupt enabled (Register 0x02[7])
WRITE LEDC1[3:0] to 0x2; // LED2 exposure configured in time slot 1
WRITE LEDC2[3:0] to 0x3; // LED3 exposure configured in time slot 2
WRITE LEDC3[3:0] to 0x0;
WRITE LEDC4[3:0] to 0x0;
WRITE LEDC5[3:0] to 0x0;
WRITE LEDC6[3:0] to 0x0;
WRITE SHDN[0] to 0x0; // Start Sampling STOP;

www.maximintegrated.com Maxim Integrated │  20

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Pseudo-Code for Interrupt Handling with FIFO_A_FULL

The following pseudo-code shows an example on handling the Interrupt when using the A_FULL Interrupt.
Interrupt handlervoid irqHandler(void)
{
uint8_t intStatus;
//Read Status
ReadReg(0x00, &intStatus);
if ( intStatus& 0x80 ) { //A FULL RDY
device_data_read(); //Data Read Routine
}
Pseudo-Code Example of Reading Data from FIFO
Example pseudo-code for reading data from FIFO when using a single photodiode channel and two LED channels.
void device_data_read(void) {
uint8_t sampleCnt;
uint8_t regVal;
uint8_t dataBuf[128*2*3]; //128 FIFO samples, 2 channel, 3 byte/channel
int led1[32];
int led2[32];
ReadReg(0x07, &sampleCnt);
//Read FIFO
ReadFifo(dataBuf, sampleCnt * 3);
int i = 0;
for ( i = 0; i < sampleCnt; i++ ) {
led1[i] = ((dataBuf[i*6+0] << 16 ) | (dataBuf[i*6+1] << 8) | (dataBuf[i*6+2]))
& 0x7ffff;
led2[i] = ((dataBuf[i*6+3] << 16 ) | (dataBuf[i*6+4] << 8) | (dataBuf[i*6+5]))
& 0x7ffff;
}
}
Example pseudo-code for reading data from FIFO when using dual photodiode channels and two LED channels.
void device_data_read(void) {
uint8_t sampleCnt;
uint8_t regVal;
uint8_t dataBuf[128*2*2*3]; //128 FIFO samples, 2 channel, 2 PD, 3 byte/channel
int led1A[32];
int led1B[32];
int led2A[32];
int led2B[32];
ReadReg(0x07, &sampleCnt);

www.maximintegrated.com Maxim Integrated │  21

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

//Read FIFO
ReadFifo(dataBuf, sampleCnt * 3);
int i = 0;
for ( i = 0; i < sampleCnt; i++ ) {
led1A[i] = ((dataBuf[i*12+0] << 16 ) | (dataBuf[i*12+1] << 8) | (dataBuf[i*12+2]))
& 0x7ffff; // LED1, PD1
led1B[i] = ((dataBuf[i*12+3] << 16 ) | (dataBuf[i*12+4] << 8) | (dataBuf[i*12+5]))
& 0x7ffff; // LED1, PD2
led2A[i] = ((dataBuf[i*12+6] << 16 ) | (dataBuf[i*12+7] << 8) | (dataBuf[i*12+8]))
& 0x7ffff; // LED2, PD1
led2B[i] = ((dataBuf[i*12+9] << 16 ) | (dataBuf[i*12+10] << 8) | (dataBuf[i*12+11]))
& 0x7ffff; // LED2, PD2
}
}

Optical Timing ent measurement can be used to adjust the LED drive
The MAXM86161 optical controller is capable of being level to compensate for increased noise levels when high
configured to make a variety of measurements. Each LED interfering ambient signals are present.
exposure is ambient light compensated before the ADC The following optical timing diagrams illustrate several
conversion. possible measurement configurations.
The controller can be configured to pulse one, two, or One LED Pulsing with No Direct Ambient Sampling
three LED drivers sequentially so as to make measure-
The optical timing diagram below represents just LED1
ments at multiple wavelengths as is done in pulse oximetry
pulsing during the exposure time with no direct ambient
measurements or simultaneously to drive multiple LEDs
sampling enabled. This timing mode would be used when
such as is done with heart rate measurements on the
heart rate is being measured with a single green LED. In
wrist.
this mode, a single optical sampled value appears suc-
The controller is also configurable to measure direct cessively in the FIFO.
ambient level for every exposure sample. The direct ambi-

tPW
LED1_DRV
tSAMPLE

LED2_DRV

LED3_DRV
tLED_SETLNG

LED1 LED1
PD_SAMPLE EXPOSURE EXPOSURE
SAMPLE SAMPLE

tINT
NOTE: LED IS ON WHEN LEDx_DRV IS LOW

Figure 1. Timing for LED1 Pulsing with No Direct Ambient Sampling

www.maximintegrated.com Maxim Integrated │  22

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

One LED Pulsing with Direct Ambient Sampling Two LEDs Pulsing Sequentially with Direct
The optical timing diagram below represents just LED1 Ambient Sampling
pulsing during the exposure time with direct ambient The timing diagram below illustrates the optical timing
sampling enabled. This timing mode would be used when when both LED1 and LED2 are enabled to pulse sequen-
heart rate is being measured with a single green LED. In tially. Direct ambient sampling is also enabled. This tim-
this mode, a single optical sampled value, followed by the ing mode would be used when SpO2 is being measured
ambient sampled value appears successively in the FIFO. with IR and red LEDs. When SpO2 is being measured
with IR and red LEDs, the optical sampled value for each
LED appears successively, followed by the direct ambient
sampled value in the FIFO.

tPW
LED1_DRV
tSAMPLE

LED2_DRV

LED3_DRV
tLED_SETLNG

LED1 DIRECT LED1

PD_SAMPLE EXPOSURE AMBIENT EXPOSURE
SAMPLE SAMPLE SAMPLE

tINT tINT
NOTE: LED IS ON WHEN LEDx_DRV IS LOW

Figure 2. Timing for LED1 Pulsing with Direct Ambient Sampling

tPW
LED1_DRV
tSAMPLE

tPW
LED2_DRV

LED3_DRV
tLED_SETLNG tLED_SETLNG

LED1 LED2 DIRECT LED1

PD_SAMPLE EXPOSURE EXPOSURE AMBIENT EXPOSURE
SAMPLE SAMPLE SAMPLE SAMPLE

tINT tINT tINT

NOTE: LED IS ON WHEN LEDx_DRV IS LOW

Figure 3. Timing for LED1 and LED2 Pulsing Sequentially with Direct Ambient Sampling

www.maximintegrated.com Maxim Integrated │  23

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

All LEDs Pulsing Sequentially with Direct In addition to algorithmically reducing the sub-DAC tran-
Ambient Sampling sitions, the MAXM86161 incorporates a self-calibration
The optical timing diagram below illustrates the three scheme that can be used to further reduce the sub-DAC
LEDs pulsing sequentially, followed by a direct ambient XNL errors. To run self-calibration, the following setup
sample. This timing mode would be used when the heart procedure should be used:
rate on a green LED is combined with an SpO2 measure- 1) Write 0x00 to the following register addresses: 0x02,
ment using IR and RED LEDs. 0x03, 0x0D, 0x10, 0x12, 0x13, 0x20.
ADC Architecture and Transfer Function 2) Set the PPG1_ADC_RGE and PPG_TINT bit fields in
Non-Linearity (XNL) Trim the PPG_Configuration1 register 0x11 to the values
MAXM86161 is comprised of a 16-bit current integrat- required for the intended application.
ing incremental delta-sigma analog-to-digital converter 3) Set the START_CAL bit to one on the DAC Calibra-
(ADC), wrapped in a 5-bit subranging digital-to-analog tion Enable register 0x50.
converter (DAC). The subranging DAC is scaled to have 4) Wait for 200ms for the self-calibration procedure to
two bits of redundancy, resulting in an overall dynamic complete.
range of 19 bits.
5) Monitor the CAL_DAC_Complete bit in the DAC
The native delta-sigma ADC linearity is exceptional. Calibration Enable register to go high, indicating the
However, the subranging DAC uses a unary architecture calibration procedure is complete.
which has some mismatch between unit current sources
6) Check the CAL_DAC1_OOR and bits in the DAC
of the DAC and the ADC reference current. This mismatch
Calibration Enable register to verify that self-
results in some transfer function nonlinearity (XNL) errors
calibration has completed successfully.
when the sub-DAC code transitions. For this reason, the
sub-ranging DAC algorithm is designed to minimize DAC 7) Configure the registers 0x02, 0x03, 0x0D, 0x10, 0x12,
transitions by introducing large hysteresis through the and 0x13 in any order for the application intended.
overlapping sub-DAC ranges. Consequently, under nor- 8) Finally, write register 0x20 to start the MAXM86161
mal PPG operation, the sub-DAC does not transition and measurement sequence.
the linearity of the converter signal is driven entirely by the
linear native delta-sigma ADC.

tPW
LED1_DRV
tSAMPLE

tPW
LED2_DRV

tPW
LED3_DRV
tLED_SETLNG tLED_SETLNG tLED_SETLNG

LED1 LED2 LED3 DIRECT LED1

PD_SAMPLE EXPOSURE EXPOSURE EXPOSURE AMBIENT EXPOSURE
SAMPLE SAMPLE SAMPLE SAMPLE SAMPLE

tINT tINT tINT tINT

NOTE: LED IS ON WHEN LEDx_DRV IS LOW

Figure 4. Timing for LED1, LED2, and LED3 Pulsing Sequentially with Direct Ambient Sampling

www.maximintegrated.com Maxim Integrated │  24

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

To further support dealing with the residual sub-DAC MAXM86161 power to a minimum during situations where
XNL error, which appears as a small offset shift when the there is no reflective returned signal. It is also intended to
sub-DAC transitions, an optional FIFO tag value can be reduce the emitted light to a minimum or even below that
enabled. This optional FIFO tag is enabled through the perceivable by the human eye.
DAC_CODE_CHG_TAG bit in the PPG_Sync_Control When the proximity mode is enabled and the measure-
register (0x10). When enabled, the FIFO outputs a tag ment assigned to LEDC1 with the LED current in PILOT_
value of 0x1D on every conversion on which the sub-DAC PA exceeds the PROX_INT_THRESH, the MAXM86161
transitions. This tag value overrides the normal outputted also generates a Proximity Detect Interrupt (register
tag for that conversion, thus allowing the conversion on 0x01[4]). In such an event, MAXM86161 switches to nor-
which the sub-DAC update occurred to be located in the mal mode, changing the sample rate to that assigned in
FIFO. One application of this feature would be to trigger PPG Configuration 2 register (0x12) bit field PPG_SR and
special backend software handling for the conversions on the LED current assigned to the measurement of LEDC1.
which the sub-DAC update occurs to compensate for the Thus, the MAXM86161 is able to switch to proximity
residual error. mode and back to normal mode without microprocessor
Proximity Mode Function interaction.
The MAXM86161 includes an optical proximity function The threshold applied to PROX_INT_THRESH should be
which could significantly reduce energy consumption and well below that of a usable signal at the maximum LED
extend battery life when the sensor is not in contact with current applied to LEDC1 but high enough to not be trig-
the skin. Proximity mode is enabled by setting the PROX_ gered by noise from distant objects. Further, the current
INT_EN bit field to 1 in the Interrupt Enable 2 register assigned to PILOT_PA should be much lower than that
(0x02[4]), setting a threshold in the PROX_INT_THRESH assigned to LEDx_PA in normal mode. This ensures that
register (0x14) and assigning an LED current in the the signal obtained from LEDC1 drops significantly when
PILOT_PA (0x29). Proximity mode also requires that LED entering proximity mode; thus, providing enough hyster-
Sequence Register 1, field LEDC1 (address [3:0]) to be esis to eliminate multiple interrupts being generated at the
assigned to a specific measurement and that measure- proximity-normal mode transition.
ment is correctly connected to a light source. The LEDC1 To guarantee that MAXM86161 successfully transitions
measurement is used to detect the optical presents of a from proximity mode to normal mode, the PROX_INT_
reflecting object in proximity mode and thus must be valid THRESH should be low enough and the PILOT_PA high
for proximity mode to work. enough to ensure that the device mounted on the darkest
When enabled, the Proximity Detect Interrupt (register of skins returns a signal above the PROX_INT_THRESH
0x01[4]) is asserted and proximity mode is entered when at the PILOT_PA current.
the value of the measurement assigned to LEDC1 drops Note that proximity mode is only available to LEDC1 mea-
below the PROX_INT_THRESH. When entering proximity surements that are made with PD1_IN optical channel
mode, the MAXM86161 drops the current to the LED(s) without an external mux. When proximity mode is active,
assigned to LEDC1 to PILOT_PA value, reduce the sam- LEDC2 to LEDC6 is ignored. The threshold applied to the
ple rate to 8sps and operates in Low Power mode. The PROX_INT_THRESH register are in units of 2048LSBs.
intent is to both reduce the consumed LED current and

www.maximintegrated.com Maxim Integrated │  25

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

SENSOR INITIALIZED
WITH PROX MODE ON
(PROX_INT_EN = 1)

PROX MODE
(LED ASSIGNED TO
LEDC1 TURNED ON
BASED ON PILOT_PA
SETTINGS) Note1
REMAINS IN
PROX MODE
NO

ADC COUNT
> PROXIMITY MODE
THRESHOLD? Note2

YES (OBJECT DETECTED)

PROX_INT
ASSERTED EXIT PROX MODE
+
PROX_INT CLEARED BY
READING INTERRUPT STATUS 1
ENTER THE NORMAL
REGISTER +
DATA ACQUISITIONNote3 FIFO_DATA FLUSHED
RE-ENTER
PROX MODE HOST READ OUT
FIFO_DATA

NO

ADC COUNT
< PROXIMITY MODE
THRESHOLD? Note2 ENTER PROX MODE
+
PROX_INT CLEARED BY
READING INTERRUPT STATUS 1
REGISTER
PROX_INT +
ASSERTED FIFO_DATA FLUSHED

Note 1: SAMPLE RATE = 8sps, AND OPERATES IN LOW POWER MODE DURING PROX MODE.
Note 2: PROXIMITY MODE THRESHOLD = PROX_INT_THRESH * 2048
Note 3: CONFIGURATIONS AS DEFINED IN LEDx_PA[7:0] AND PPG_SR[4:0]

Figure 5. Proximity Function Flow Diagram

Picket Fence Detect-and-Replace Function passes under a bridge and into a dark shadow. In these
Under typical situations, the rate of change of ambient light situations, it is possible for the MAXM86161 ambient light
is such that the ambient signal level during exposure can correction (ALC) circuit to fail and produce an erroneous
be accurately predicted and high levels of ambient rejec- estimation of the ambient light during the exposure inter-
tion are obtained. However, it is possible to have situations val. The MAXM86161 has a built-in algorithm called the
where the ambient light level changes extremely rapidly, picket fence function that corrects the final PPG results in
for example when in a car with direct sunlight exposure case of ALC circuit failure due to these extreme conditions.

www.maximintegrated.com Maxim Integrated │  26

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

The picket fence function works on the basis that the IIR_INIT_VALUE bits control the initial values for the IIR
extreme conditions causing a failure of the ALC are low-pass filter when the algorithm is initialized.
rare events. These events resulting in a large deviation When a picket fence event is detected, the option of how
from the past sample history of a normal PPG riding to extrapolate the correct point is again controlled by the
on a motion effect signal, which normally would change PF_ORDER bit. This point can be identical as the previ-
relatively slowly with respect to the sampling interval. ous point (PF_ORDER = 0) or a least square fit extrapo-
Under these conditions, it is possible to detect sample lation based on the previous four ADC converted points
values that are well outside the normal sample-to-sample (PF_ORDER = 1).
deviation and replace those samples with an extrapolated
value based on the relatively recent history of samples. Figure 6 illustrates the function in block diagram form. If
the picket fence algorithm is enabled (bit PF_ENABLE
The picket fence function is enabled by setting PF_ = 1), the input from the ADC, s(n) generates p(n) in a
ENABLE (0x16[7]) bit to 1. The power-on reset default way that is dependent on the value of the PF_ORDER
of MAXM86161 has the picket fence function disabled. bit. Value s(n) is subtracted from p(n) and turned into a
The function begins with detecting a picket fence event. positive number d(n) and fed into the IIR low pass filter
Detection is done by taking the absolute value of the dif- producing value lpf(n). The output of the low-pass filter
ference between the present ADC converted value at a lpf(n) is then multiplied by a user constant, THRESHOLD_
predicted point, called an estimation error, and comparing SIGMA_MULT to produce the picket fence threshold,
this estimation error to a threshold. If the estimation error PFT(n). The value d(n) is then compared to this threshold
exceeds the threshold, then the present ADC converted and if greater than the PFT(n), the point s(n) is replaced
point is considered a picket fence event. with the point p(n).
The predicted point referred to above is computed in one This scheme essentially produces a threshold that tracks
of two ways, set by the value in the PF_ORDER (0x16[6]) the past returned optical signal with a bandwidth based
bit. If PF_ORDER = 0 the predicted point is simply the on the past historical change sample-to-sample. Figure 7
previous ADC converted point. If PF_ORDER = 1 the pre- below illustrates graphically how the threshold detection
dicted point is a least square fit extrapolation based on the scheme works on a real PPG signal. Note that the black
previous four picket fence outputs, which under normal trace is the real ADC sample point, the red traces are the
circumstances is identical to the ADC converted inputs. output of the low-pass filter of the error estimation mir-
The threshold used in detecting a picket fence event is a rored around the ADC points, and the blue traces are the
low passed version of the running estimation error com- threshold values.
puted above times a multiplier. The multiplier used is set The recommended settings for the picket fence algorithm
by the THRESHOLD_SIGMA_MULT (0x16[1:0]) bits and are the default power on reset values for all registers but
can be 4, 8, 16, or 32 times the running low-passed filter THRESHOLD_SIGMA_MULT bits. Here it is recommend-
output of the estimation error. ed that the 32x value 0x3 is used so only large excursions
The low-pass filter function is controlled by two param- are classified as picket fence events. Lower values of
eters, the IIR_TC (0x16[5:4]) bits and IIR_INIT_VALUE THRESHOLD_SIGMA_MULT can cause the algorithm to
(0x16[3:2]) bits. The IIR_TC bits control the filters time go off track with extremely noisy waveforms.
constant and are adjustable from 8 to 64 samples. The

www.maximintegrated.com Maxim Integrated │  27

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

s(n) p(n) Note1

INPUT SAMPLE PREDICTED SAMPLE
IIR_INIT_VALUE

- IIR LOW-FILTER

IIR_TC

d(n) Note2 lpf(n)

THRESHOLD_SIGMA_MULT

PICKET EVENT
PICKET FENCE
NOT DETECTED NO d(n) > PFT ?
THRESHOLD, PFT(n)
DOUT=s(n)

YES

PICKET EVENT
DETECTED
DOUT=p(n)

Note 1: If PG_ORDER = 0, p(n) = s(n-1). If PG_ORDER = 1, p(n) = s(n - 1) + 0.5s(n - 2) - 0.5s(n - 4)

Note 2: d(n) = ABS [ p(n) - s(n) ]

Figure 6. Picket Fence Function Flow

# 10
5 Picket Fence Algorithm Variables

Raw PPG
1.46 PPG+Estimation
PPG-Estimation
PPG+Threshod
PPG-Threshold
1.44

1.42

1.4

1.38
ADC Codes (LSB)

1.36

1.34

1.32 Transient That Does Qualify

As A Picket Fence Event

Figure 7. Picket Fences Variables

1.3 In A PPG Waveform

1.28 Transient That Does Qualify

As A Picket Fence Event

www.maximintegrated.com Maxim Integrated │  28

18 20 22 24 26 28 30 32 34
Time (sec)
MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Layout Guidelines 4) VREF and VLDO pins should be decoupled to the

MAXM86161 is a high dynamic range analog front-end PCB GND plane with a 1.0μF ceramic capacitor. The
(AFE) and its performance can be adversely impacted by voltage on the VREF pin is nominally 1.21V and that
the physical printed circuit board (PCB) layout. See the for VLDO is nominally 1.8V, so a 6.3V rated ceramic
below layout recommendations for detail. capacitor should be adequate for this purpose.
1) All bypass capacitors should be placed as close to 5) Shield the vias with board ground plane.
the part as possible. 6) Use short and low resistance trace for VLED and all
2) All LEDx_DRV pins should be soldered down for GND.
mechanical stability (the Maxim layout example has 7) All decoupling capacitors use individual vias to the
three TPs for debug purposes only). PCB GND plane to avoid coupling between decou-
3) GND_ANA, GND_DIG, and PGND should be pled supplies when sharing vias.
shorted to a single PCB GND plane. These three
pins have been assigned along a single column so
they can be easily shorted

Figure 8. Layout Guideline

www.maximintegrated.com Maxim Integrated │  29

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

I2C/SMBus Compatible Serial Interface Bit Transfer

The MAXM86161 features an I2C/SMBus compatible, One data bit is transferred during each SCL cycle. The
2-wire serial interface consisting of a serial data line data on SDA must remain stable during the high period
(SDA) and a serial clock line (SCL). SDA and SCL facili- of the SCL pulse. Changes in SDA while SCL is high are
tate communication between the MAXM86161 and the control signals (see the START and STOP Conditions
master at clock rates up to 400kHz. section).
Figure 9 shows the 2-wire interface timing diagram. The START and STOP Conditions
master generates SCL and initiates data transfer on the SDA and SCL idle high when the bus is not in use. A mas-
bus. The master device writes data to the MAXM86161 ter initiates communication by issuing a START condition.
by transmitting the proper slave address followed by the A START condition is a high-to-low transition on SDA with
register address and then the data word. Each transmit SCL high. A STOP condition is a low-to-high transition on
sequence is framed by a START (S) or REPEATED SDA while SCL is high (Figure 10). A START condition
START (Sr) condition and a STOP (P) condition. Each from the master signals the beginning of a transmission
word transmitted to the MAXM86161 is 8 bits long and to the MAXM86161. The master terminates transmission,
is followed by an acknowledge clock pulse. A master and frees the bus, by issuing a STOP condition. The bus
reading data from the MAXM86161 transmits the proper remains active if a REPEATED START condition is gener-
slave address followed by a series of nine SCL pulses. ated instead of a STOP condition.
The MAXM86161 transmits data on SDA in sync with
the master-generated SCL pulses. The master acknowl- Early STOP Conditions
edges receipt of each byte of data. Each read sequence The MAXM86161 recognizes a STOP condition at any
is framed by a START (S) or REPEATED START (Sr) point during data transmission except if the STOP condi-
condition, a not acknowledge, and a STOP (P) condition. tion occurs in the same high pulse as a START condition.
SDA operates as both an input and an open-drain output. For proper operation, do not send a STOP condition dur-
A pullup resistor is required on SDA. SCL operates only ing the same SCL high pulse as the START condition.
as an input. A pullup resistor is required on SCL if there
Slave Address
are multiple masters on the bus, or if the single master
has an open-drain SCL output. Series resistors in line with The slave address is defined as the seven most sig-
SDA and SCL are optional. Series resistors protect the nificant bits (MSBs) followed by the read/write bit. For
digital inputs of the MAXM86161 from high voltage spikes the MAXM86161 the seven most significant bits are
on the bus lines, and minimize crosstalk and undershoot 0b1100010X. Where X is determined by the read/write bit.
of the bus signals. For read mode, set the read/write bit to 1. For write mode,
set the read/write bit to 0. The address is the first byte of
Detailed I2C Timing Diagram information sent to the IC after the START condition.
The detailed timing diagram of various electrical charac-
teristics is shown in Figure 9.

SDA
tSU, STA
tBUF
tSU, DAT tHD, STA tSU, STO
tSP
tLOW tHD, DAT

SCL

tHIGH
tR tF
tHD, STA

START REPEATED START STOP START

CONDITION CONDITION CONDITION CONDITION

Figure 9. Detailed I2C Timing Diagram

www.maximintegrated.com Maxim Integrated │  30

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Acknowledge Bit event of an unsuccessful data transfer, the bus master

The acknowledge bit (ACK) is a clocked 9th bit that the retries communication. The master pulls down SDA dur-
MAXM86161 uses to handshake receipt of each byte of ing the 9th clock cycle to acknowledge receipt of data
data when in write mode (Figure 11). The MAXM86161 when the MAXM86161 is in read mode. An acknowledge
pulls down SDA during the entire master-generated 9th is sent by the master after each read byte to allow data
clock pulse if the previous byte is successfully received. transfer to continue. A not-acknowledge is sent when the
Monitoring ACK allows for detection of unsuccessful data master reads the final byte of data from the MAXM86161
transfers. An unsuccessful data transfer occurs if a receiv- followed by a STOP condition.
ing device is busy or if a system fault has occurred. In the

S Sr P

SCL

SDA

Figure 10. I2C START, STOP, and REPEATED START Conditions

SDA
tSU, STA
tBUF
tSU, DAT tHD, STA tSU, STO
tSP
tLOW tHD, DAT

SCL

tHIGH
tR tF
tHD, STA

START REPEATED START STOP START

CONDITION CONDITION CONDITION CONDITION

Figure 11. I2C Acknowledge Bit

www.maximintegrated.com Maxim Integrated │  31

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

I2C Write Data Format The second byte transmitted from the master configures
A write to the MAXM86161 includes transmission of a the MAXM86161 internal register’s address pointer. The
START condition, the slave address with the R/W bit set pointer tells the MAXM86161 where to write the next byte
to 0, one byte of data to configure the internal register of data. An acknowledge pulse is sent by the MAXM86161
address pointer, one or more bytes of data, and a STOP upon receipt of the address pointer data.
condition. Figure 12 illustrates the proper frame format The third byte sent to the MAXM86161 contains the data
for writing one byte of data to the MAXM86161. Figure 13 that is written to the chosen register. An acknowledge
illustrates the frame format for writing n-bytes of data to pulse from the MAXM86161 signals receipt of the data
the MAXM86161. byte. The address pointer auto increments to the next
The slave address with the R/W bit set to 0 indicates that register address after each received data byte. This auto-
the master intends to write data to the MAXM86161. The increment feature allows a master to write to sequential
MAXM86161 acknowledges receipt of the address byte registers within one continuous frame. The master sig-
during the master-generated 9th SCL pulse. nals the end of transmission by issuing a STOP condition.
The auto-increment feature is disabled when there is an
attempt to write to the FIFO_DATA register.

R/W
S 1 1 0 0 0 1 1 ACK A7 A6 A5 A4 A3 A2 A1 A0 ACK
=0

SLAVE ID REGISTER ADDRESS

D7 D6 D5 D4 D3 D2 D1 D0 ACK P

DATA BYTE

S = START CONDITION
P= STOP CONDITION
ACK = ACKNOWLEDGE BY THE RECEIVER INTERNAL ADDRESS POINTER AUTO-INCREMENT(FOR
WRITING MULTIPLE BYTES)

Figure 12. I2C Single Byte Write Transaction

www.maximintegrated.com Maxim Integrated │  32

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

R/W
S 1 1 0 0 0 1 1 ACK A7 A6 A5 A4 A3 A2 A1 A0 ACK
=0

SLAVE ID REGISTER ADDRESS

D7 D6 D5 D4 D3 D2 D1 D0 ACK D7 D6 D5 D4 D3 D2 D1 D0 ACK …..

DATA BYTE 1 DATA BYTE 2

D7 D6 D5 D4 D3 D2 D1 D0 ACK D7 D6 D5 D4 D3 D2 D1 D0 ACK P

DATA BYTE n-1 DATA BYTE n

S = START CONDITION
P= STOP CONDITION INTERNAL ADDRESS POINTER AUTO-INCREMENT(FOR
ACK = ACKNOWLEDGE BY THE RECEIVER WRITING MULTIPLE BYTES)

Figure 13. I2C Multi-Byte Write Transaction

I2C Read Data Format The address pointer can be preset to a specific register
Send the slave address with the R/W bit set to 1 to initiate before a read command is issued. The master presets the
a read operation. The MAXM86161 acknowledges receipt address pointer by first sending the MAXM86161 slave
of its slave address by pulling SDA low during the 9th SCL address with the R/W bit set to 0 followed by the register
clock pulse. A START command followed by a read com- address. A REPEATED START condition is then sent fol-
mand resets the address pointer to register 0x00. lowed by the slave address with the R/W bit set to 1. The
MAXM86161 then transmits the contents of the specified
The first byte transmitted from the MAXM86161 is the
register. The address pointer auto-increments after trans-
contents of register 0x00. Transmitted data is valid on the
mitting the first byte.
rising edge of SCL. The address pointer auto-increments
after each read data byte. This auto-increment feature The master acknowledges receipt of each read byte
allows all registers to be read sequentially within one during the acknowledge clock pulse. The master must
continuous frame. The auto-increment feature is disabled acknowledge all correctly received bytes except the last
when there is an attempt to read from the FIFO_DATA byte. The final byte must be followed by a not acknowledge
register. A STOP condition can be issued after any num- from the master and then a STOP condition. Figure 14
ber of read data bytes. If a STOP condition is issued fol- illustrates the frame format for reading one byte from the
lowed by another read operation, the first data byte to be MAXM86161. Figure 15 illustrates the frame format for
read is from register 0x00. reading multiple bytes from the MAXM86161.

www.maximintegrated.com Maxim Integrated │  33

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

R/W
S 1 1 0 0 0 1 1 ACK A7 A6 A5 A4 A3 A2 A1 A0 ACK
=0

SLAVE ID REGISTER ADDRESS

R/W
Sr 1 1 0 0 0 1 1 ACK D7 D6 D5 D4 D3 D2 D1 D0 NACK P
=1

SLAVE ID DATA BYTE

S = START CONDITION
Sr = REPEATED START CONDITION
P= STOP CONDITION
ACK = ACKNOWLEDGE BY THE RECEIVER
NACK = NOT ACKNOWLEDGE

Figure 14. I2C Single Byte Read Transaction

R/W
S 1 1 0 0 0 1 1 ACK A7 A6 A5 A4 A3 A2 A1 A0 ACK
=0

SLAVE ID REGISTER ADDRESS

R/W
Sr 1 1 0 0 0 1 1 ACK D7 D6 D5 D4 D3 D2 D1 D0 AM
=1

SLAVE ID DATA 1

D7 D6 D5 D4 D3 D2 D1 D0 AM D7 D6 D5 D4 D3 D2 D1 D0 NACK P

DATA n-1 DATA n

S = START CONDITION
Sr = REPEATED START CONDITION
P= STOP CONDITION
ACK = ACKNOWLEDGE BY THE RECEIVER
NACK = NOT ACKNOWLEDGE
AM = ACKNOWLEDGE BY THE MASTER

Figure 15. I2C Multibyte Read Transaction

www.maximintegrated.com Maxim Integrated │  34

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Register Map
ADDRESS NAME MSB LSB
STATUS
DIE_
DATA_ ALC_ PROX_ LED_ PWR_
0x00 Interrupt Status 1[7:0] A_FULL TEMP_ –
RDY OVF INT COMPB RDY
RDY
SHA_
0x01 Interrupt Status 2[7:0] – – – – – – –
DONE
DIE_
A_ DATA_ ALC_ LED_
PROX_ TEMP_
0x02 Interrupt Enable 1[7:0] FULL_ RDY_ OVF_ OMPB_ – –
INT_EN RDY_
EN EN EN EN
EN
SHA_
0x03 Interrupt Enable 2[7:0] – – – – – – – DONE_
EN
FIFO
0x04 FIFO Write Pointer[7:0] – FIFO_WR_PTR[6:0]
0x05 FIFO Read Pointer[7:0] – FIFO_RD_PTR[6:0]
0x06 Over Flow Counter[7:0] – OVF_COUNTER[6:0]
0x07 FIFO Data Counter[7:0] FIFO_DATA_COUNT[7:0]
0x08 FIFO Data Register[7:0] FIFO_DATA[7:0]
0x09 FIFO Configuration 1[7:0] – FIFO_A_FULL[6:0]
TIME_ FIFO_ A_
FLUSH_ FIFO_
0x0A FIFO Configuration 2[7:0] – – STAMP_ STAT_ FULL_ –
FIFO RO
EN CLR TYPE
SYSTEM CONTROL
SIN-
LP_
0x0D System Control[7:0] – – – – GLE_ SHDN RESET
MODE
PPG
PPG CONFIGURATION
DAC_
TIME_ SW_
CODE_
0x10 PPG Sync Control[7:0] STAMP_ – FORCE_ GPIO_CTRL[3:0]
CHG_
EN SYNC
TAG
ALC_ ADD_
PPG1_PPG1_
0x11 PPG Configuration 1[7:0] DIS- OFF- – PPG_TINT[1:0]
ADC_RGE[1:0]
ABLE SET
0x12 PPG Configuration 2[7:0] PPG_SR[4:0] SMP_AVE[2:0]
DIG_
BURST_
0x13 PPG Configuration 3[7:0] LED_SETLNG[1:0] FILT_ – – BURST_RATE[1:0]
EN
SEL
0x14 Prox Interrupt Threshold[7:0] PROX_INT_THRESH[7:0]
0x15 Photo Diode Bias[7:0] – – – PDBIAS1[2:0]
PPG PICKET FENCE DETECT AND REPLACE
PF_EN- PF_OR- IIR_INIT_VAL- THRESHOLD_
0x16 Picket Fence[7:0] IIR_TC[1:0]
ABLE DER UE[1:0] SIGMA_MULT[1:0]

www.maximintegrated.com Maxim Integrated │  35

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Register Map (continued)

ADDRESS NAME MSB LSB
LED SEQUENCE CONTROL
0x20 LED Sequence Register 1[7:0] LEDC2[3:0] LEDC1[3:0]
0x21 LED Sequence Register 2[7:0] LEDC4[3:0] LEDC3[3:0]
0x22 LED Sequence Register 3[7:0] LEDC6[3:0] LEDC5[3:0]
LED PULSE AMPLITUDE
0x23 LED1 PA[7:0] LED1_DRV[7:0]
0x24 LED2 PA[7:0] LED2_DRV[7:0]
0x25 LED3_PA[7:0] LED3_DRV[7:0]
0x29 LED PILOT PA[7:0] PILOT_PA[7:0]
0x2A LED Range 1[7:0] – – LED3_RGE[1:0] LED2_RGE[1:0] LED1_RGE[1:0]
PPG1_HI_RES_DAC
S1_
HRES_
0x2C S1 HI RES DAC1[7:0] – S1_HRES_DAC1[5:0]
DAC1_
OVR
S2_
HRES_
0x2D S2 HI RES DAC1[7:0] – S2_HRES_DAC1[5:0]
DAC1_
OVR
S3_
HRES_
0x2E S3 HI RES DAC1[7:0] – S3_HRES_DAC1[5:0]
DAC1_
OVR
S4_
HRES_
0x2F S4 HI RES DAC1[7:0] – S4_HRES_DAC1[5:0]
DAC1_
OVR
S5_
HRES_
0x30 S5 HI RES DAC1[7:0] – S5_HRES_DAC1[5:0]
DAC1_
OVR
S6_
HRES_
0x31 S6 HI RES DAC1[7:0] – S6_HRES_DAC1[5:0]
DAC1_
OVR
DIE TEMPERATURE
Die Temperature TEMP_
0x40 – – – – – – –
Configuration[7:0] EN
0x41 Die Temperature Integer[7:0] TEMP_INT[7:0]
0x42 Die Temperature Fraction[7:0] – – – – TEMP_FRAC[3:0]
DAC CALIBRATION
CAL_
CAL_
DAC_ START_
0x50 DAC Calibration Enable[7:0] – – DAC1_ – – –
Com- CAL
OOR
plete

www.maximintegrated.com Maxim Integrated │  36

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Register Map (continued)

ADDRESS NAME MSB LSB
SHA256
0xF0 SHA Command[7:0] SHA_CMD[7:0]
SHA_ SHA_
0xF1 SHA Configuration[7:0] – – – – – –
EN START
MEMORY
MEM_ BANK_
0xF2 Memory Control[7:0] – – – – – –
WR_EN SEL
0xF3 Memory Index[7:0] MEM_IDX[7:0]
0xF4 Memory Data[7:0] MEM_DATA[7:0]
PART ID
0xFE Revision ID[7:0] – – – – – – – –
0xFF Part ID[7:0] PART_ID[7:0]

Register Details
INTERRUPT STATUS 1 (0x00)
BIT 7 6 5 4 3 2 1 0
LED_ DIE_TEMP_
Field A_FULL DATA_RDY ALC_OVF PROX_INT – PWR_RDY
COMPB RDY
Reset 0x0 0x0 0x0 0x0 0x0 0x0 – 0x0
Access Type Read Only Read Only Read Only Read Only Read Only Read Only – Read Only

A_FULL
This is a read-only bit. This bit is cleared by reading the Interrupt Status 1 Register. It is also cleared when FIFO_DATA
register is read if FIFO_STAT_CLR = 1.

VALUE ENUMERATION DECODE

0 OFF Normal Operation
Indicates that the FIFO buffer will overflow the threshold set by FIFO_A_FULL[6:0] on the next
1 ON
sample.

DATA_RDY
This is a read-only bit and it is cleared by reading the Interrupt Status 1 register (0x00). It is also cleared by reading
the FIFO_DATA register if FIFO_STAT_CLR = 1

VALUE ENUMERATION DECODE

0 OFF Normal Operation
1 ON This interrupt triggers when there is a new data in the FIFO.

www.maximintegrated.com Maxim Integrated │  37

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

ALC_OVF
This is a read-only bit. The interrupt is cleared by reading the Interrupt Status 1 register (0x00).

VALUE ENUMERATION DECODE

0 OFF Normal Operation
This interrupt triggers when the ambient light cancellation function of the photodiode has
1 ON reached its maximum limit due to overflow, and therefore, ambient light is affecting the output of
the ADC.

PROX_INT
If PROX_INT_EN is 0, then the prox mode is disabled and the exposure sequence configured in LED Sequence Control Registers
begins immediately. This bit is cleared when the Interrupt Status 1 Register is read.

VALUE ENUMERATION DECODE

0 OFF Normal Operation
Indicates that the ADC reading of the LED configured in LEDC1 has crossed the proximity
1 ON
threshold.

LED_COMPB
LED is not compliant. At the end of each sample, if the LED Driver is not compliant, LED_COMPB interrupt is asserted
if LED_COMPB_EN is set to 1. It is a read-only bit and is cleared when the status register is read.

VALUE ENUMERATION DECODE

0 COMPLIANT LED driver is compliant
1 NOT_COMPLIANT LED driver is not compliant

DIE_TEMP_RDY
This is a read-only bit and it is automatically cleared when the Temperature data is read or when the Interrupt Status 1
Register is read.

VALUE ENUMERATION DECODE

0 OFF Normal Operation
1 ON Indicates that the TEMP ADC has finished its current conversion.

PWR_RDY
This is a read-only bit and it indicates that VDD has gone below UVLO Threshold. This bit is not triggered by a soft
reset. This bit is cleared when Interrupt Status 1 Register is read, or by setting SHDN bit to 1.

VALUE ENUMERATION DECODE

0 OFF Normal Operation
1 ON Indicates that VBATT went below the UVLO threshold.

www.maximintegrated.com Maxim Integrated │  38

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

INTERRUPT STATUS 2 (0X01)

BIT 7 6 5 4 3 2 1 0
Field – – – – – – – SHA_DONE
Reset – – – – – – – 0x0
Access Type – – – – – – – Read Only

SHA_DONE
SHA256 Authentication Done status bit is set to 1 when the Authentication Algorithm completes. This is a read-only bit
and it gets cleared when the Status Register is read.

VALUE ENUMERATION DECODE

0x0 SHA Authentication not done
0x1 SHA Authentication done

INTERRUPT ENABLE 1 (0X02)

BIT 7 6 5 4 3 2 1 0
DATA_ ALC_OVF_ PROX_INT_ LED_ DIE_TEMP_
Field A_FULL_EN – –
RDY_EN EN EN COMPB_EN RDY_EN
Reset 0x0 0x0 0x0 0x0 0x0 0x0 – –
Access Type Write, Read Write, Read Write, Read Write, Read Write, Read Write, Read – –

A_FULL_EN

VALUE ENUMERATION DECODE

0 DISABLE A_FULL interrupt is disabled
1 ENABLE A_FULL interrupt in enabled

DATA_RDY_EN

VALUE ENUMERATION DECODE

0 DISABLE DATA_RDY interrupt is disabled
1 ENABLE DATA_RDY interrupt is enabled.

ALC_OVF_EN
VALUE ENUMERATION DECODE
0 DISABLE ALC_OVF interrupt is disabled
1 ENABLE ALC_OVF interrupt in enabled

www.maximintegrated.com Maxim Integrated │  39

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

PROX_INT_EN
When this is enabled, the exposure programmed in the LEDC1 Sequence register is used for proximity detection. If the
ADC reading for this exposure is below 2048 times the threshold programmed in PROX_INT_THRESH register, the
device is in proximity mode, otherwise it is in normal mode.
When the device is in proximity mode, the sample rate used is 8Hz, and the device starts data acquisition in pilot
mode, using only one exposure of the LED programmed in LEDC1 register, and the LED current programmed in
PILOT_PA register.
When the device is in normal mode, the sample rate used is as defined under PPG_SR register, and the device starts
data acquisition in normal mode, using all the exposures programmed in the LED Sequence registers and appropriate
LED currents.
PROX_INT interrupt is asserted when the devices enters proximity mode or normal mode if the PROX_INT_EN is pro-
grammed to 1.

VALUE ENUMERATION DECODE

0 DISABLE Proximity mode and PROX_INT interrupt are disabled
1 ENABLE Proximity mode and PROX_INT interrupt are enabled

LED_COMPB_EN

VALUE ENUMERATION DECODE

0 DISABLE LED_COMPB interrupt is disabled
1 ENABLE LED_COMPB interrupt is enabled

DIE_TEMP_RDY_EN

VALUE ENUMERATION DECODE

0 DISABLE DIE_TEMP_RDY interrupt is disabled
1 ENABLE DIE_TEMP_RDY interrupt is enabled

INTERRUPT ENABLE 2 (0X03)

BIT 7 6 5 4 3 2 1 0
SHA_
Field – – – – – – –
DONE_EN
Reset – – – – – – – 0x0
Access Type – – – – – – – Write, Read

SHA_DONE_EN
Enable SHA_DONE interrupt

VALUE ENUMERATION DECODE

0x0 DISABLE SHA_DONE interrupt disabled
0x1 ENABLE SHA_DONE interrupt enabled

www.maximintegrated.com Maxim Integrated │  40

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

FIFO WRITE POINTER (0X04)

BIT 7 6 5 4 3 2 1 0
Field – FIFO_WR_PTR[6:0]
Reset – 0x0
Access Type – Read Only

FIFO_WR_PTR
This points to the location where the next sample is to be written. This pointer advances for each sample pushed on to
the circular FIFO.
Refer to the FIFO Configuration for details.
FIFO READ POINTER (0X05)
BIT 7 6 5 4 3 2 1 0
Field – FIFO_RD_PTR[6:0]
Reset – 0x0
Access Type – Write, Read

FIFO_RD_PTR
The FIFO Read Pointer points to the location from where the processor gets the next sample from the FIFO using the
serial interface. This advances each time a sample is popped from the circular FIFO.
The processor can also write to this pointer after reading the samples. This allows rereading (or retrying) samples from
the FIFO. However writing to FIFO_RD_PTR can have adverse effects if it results in the FIFO being almost full.
Refer to the FIFO Configuration for details.
OVER FLOW COUNTER (0X06)
BIT 7 6 5 4 3 2 1 0
Field – OVF_COUNTER[6:0]
Reset – 0x0
Access Type – Read Only

OVF_COUNTER
When FIFO is full any new samples will result in new or old samples getting lost depending on FIFO_RO. OVF_
COUNTER counts the number of samples lost. It saturates at 0x7F.
Refer to the FIFO Configuration for details.
FIFO DATA COUNTER (0X07)
BIT 7 6 5 4 3 2 1 0
Field FIFO_DATA_COUNT[7:0]
Reset 0x0
Access Type Read Only

www.maximintegrated.com Maxim Integrated │  41

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

FIFO_DATA_COUNT
This is a read-only register which holds the number of items available in the FIFO for the host to read. This increments
when a new item is pushed to the FIFO, and decrements when the host reads an item from the FIFO.
Refer to the FIFO Configuration for details.
FIFO DATA REGISTER (0X08)
BIT 7 6 5 4 3 2 1 0
Field FIFO_DATA[7:0]
Reset 0x0
Access Type Read Only

FIFO_DATA
This is a read-only register and is used to get data from the FIFO. Refer to the FIFO Configuration for details.

FIFO CONFIGURATION 1 (0X09)

BIT 7 6 5 4 3 2 1 0
Field – FIFO_A_FULL[6:0]
Reset – 0x3F
Access Type – Write, Read

FIFO_A_FULL
These bits indicate how many new samples can be written to the FIFO before the interrupt is asserted. For example, if
set to 0xF, the interrupt triggers when there is 15 empty space left (113 entries), and so on.
Refer to the FIFO Configuration for details.

FIFO_A_FULL[6:0] FREE SPACE BEFORE INTERRUPT # OF SAMPLES IN FIFO

0 0 128
1 1 127
2 2 126
3 3 125
— — —
126 126 2
127 127 1

FIFO CONFIGURATION 2 (0X0A)

BIT 7 6 5 4 3 2 1 0
FLUSH_ FIFO_ A_FULL_
Field – – – FIFO_RO –
FIFO STAT_CLR TYPE
Reset – – – 0x0 0x0 0x0 0x0 –
Access Type – – – Write, Read Write, Read Write, Read Write, Read –

www.maximintegrated.com Maxim Integrated │  42

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

FLUSH_FIFO
When this bit is set to ‘1’, the FIFO gets flushed, FIFO_WR_PTR and FIFO_RD_PTR are reset to zero and FIFO_
DATA_COUNT becomes 0. The contents of the FIFO are lost.
FIFO_FLUSH is a self-clearing bit.
Refer to the FIFO Configuration for details.
FIFO_STAT_CLR
This defines whether the A-FULL interrupt should get cleared by FIFO_DATA register read.
Refer to the FIFO Configuration for details.

VALUE ENUMERATION DECODE

A_FULL and DATA_RDY interrupts do not get cleared by the FIFO_DATA register read.
0 RD_DATA_NOCLR
They get cleared by status register read.
A_FULL and DATA_RDY interrupts get cleared by FIFO_DATA register read or status
1 RD_DATA_CLR
register read.

A_FULL_TYPE
This defines the behavior of the A_FULL interrupt.

VALUE ENUMERATION DECODE

A_FULL interrupt gets asserted when the A_FULL condition is detected. It is cleared by
0 AFULL_RPT
status register read, but reasserts for every sample if the A_FULL condition persists.
A_FULL interrupt gets asserted only when the A_FULL condition is detected. The interrupt
1 AFULL_ONCE gets cleared on status register read, and does not reassert for every sample until a new
A_FULL condition is detected.

FIFO_RO
Push enable when FIFO is full:
This bit controls the behavior of the FIFO when the FIFO becomes completely filled with data.
Push to FIFO is enabled when FIFO is full if FIFO_RO = 1 and old samples are lost. Both FIFO_WR_PTR increments
for each sample after the FIFO is full. FIFO_RD_PTR also increments for each sample pushed to the FIFO.
Push to FIFO is disabled when FIFO is full if FIFO_RO = 0 and new samples are lost. FIFO_WR_PTR does not incre-
ment for each sample after the FIFO is full.
When the device is in PROX mode, push to FIFO is enabled independent of FIFO_RO setting.
Refer to the FIFO Configuration for details.

VALUE ENUMERATION DECODE

0 OFF The FIFO stops on full.
1 ON The FIFO automatically rolls over on full.

www.maximintegrated.com Maxim Integrated │  43

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

SYSTEM CONTROL (0X0D)

BIT 7 6 5 4 3 2 1 0
SINGLE_
Field – – – – LP_MODE SHDN RESET
PPG
Reset – – – – 0x0 0x0 0x0 0x0
Access Type – – – – Write, Read Write, Read Write, Read Write, Read

SINGLE_PPG
Use one PPG Channel.
In Single PPG devices, this bit is ignored. In Dual PPG devices, if this bit is 0, use two PPG channels, otherwise use
only PPG1 channel.

VALUE ENUMERATION DECODE

0x0 DUAL_PPG Both PPG channels are enabled
0x1 SINGLE_PPG Only PPG1 channel is enabled

LP_MODE
In low power mode, the sensor can be dynamically powered down between samples to conserve power. This dynamic
power down mode option only supports samples rates of 256sps and below. This mode is not available for higher sample rates.

VALUE ENUMERATION DECODE

0 OFF Dynamic power down is disabled.
Dynamic power down is enabled. The device automatically enters low power mode be-
1 ON
tween samples for sample rates 256sps and below.

SHDN
The part can be put into a power-save mode by setting this bit to one. While in power-save mode, all configuration reg-
isters retain their values, and write/read operations function as normal. All interrupts are cleared to zero in this mode.

VALUE ENUMERATION DECODE

0 OFF The part is in normal operation. No action taken.
The part can be put into a power-save mode by writing a ‘1’ to this bit. While in this mode
all configuration registers remain accessible and retain their data. ADC conversion data
contained in the registers are previous values. Writeable registers also remain accessible
1 ON
in shutdown. All interrupts are cleared. In this mode, the oscillator is shutdown and the
part draws minimum current. If this bit is asserted during an active conversion, then the
conversion is aborted.

www.maximintegrated.com Maxim Integrated │  44

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

RESET
When this bit is set, the part undergoes a forced power-on-reset sequence. All configuration, threshold and data
registers including distributed registers are reset to their power-on-state. This bit then automatically becomes ‘0’ after
the reset sequence is completed.

VALUE ENUMERATION DECODE

0 OFF The part is in normal operation. No action taken.
The part undergoes a forced power-on-reset sequence. All configuration, threshold and
1 ON data registers including distributed registers are reset to their power-on-state. This bit then
automatically becomes ‘0’ after the reset sequence is completed.

PPG SYNC CONTROL (0X10)

BIT 7 6 5 4 3 2 1 0
DAC_ SW_
TIME_
Field CODE_ – FORCE_ GPIO_CTRL[3:0]
STAMP_EN
CHG_TAG SYNC
Reset 0x0 0b0 – 0x0 0x0
Access Type Write, Read Write, Read – Write, Read Write, Read

TIME_STAMP_EN
Enable pushing TIME_STAMP to FIFO. Refer to the FIFO Configuration for details.

VALUE ENUMERATION DECODE

0x0 DISABLE TIME_STAMP is not pushed to FIFO
0x1 ENABLE TIME_STAMP is pushed to FIFO for a block of eight samples.

DAC_CODE_CHG_TAG
Override Tag with 0x1D in the FIFO when the subranging DAC code changes for the expsoure data.

VALUE ENUMERATION DECODE

0x0 FIFO has the original tags for each exposure
If DAC code for any exposure has changed in the current sample, the tag in the FIFO DATA
0x1
for that exposure is 0x1D (decimal 29).

www.maximintegrated.com Maxim Integrated │  45

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

SW_FORCE_SYNC
Writing a 1 to this bit, aborts current sample and starts a new sample. This is a self clearing bit.
GPIO_CTRL
The table below shows how the two GPIO ports are controlled for different modes of operation.
When two devices are configured to work as master-slave device pairs, they have to be configured identically for the
following configuration register fields:
●● PPG_SR
●● PPG_TINT
●● SMP_AVE
●● TIME_STAMP_EN
●● FIFO_A_FULL
●● FIFO_ROLLS_ON_FULL
Number of LED Sequence Registers (LEDC1 to LEDC6) programmed should be the same in both the devices. In
Exposure Trigger mode, if Ambient is programmed in one of the registers, it needs to be in the same LEDCx register in
both the devices.
GPIO_CTRL register for both the devices should be programmed to be either Sample Trigger or Exposure Trigger.
It is also important to configure the slave first and then the master.
DATA_RDY or A_FULL interrupt should be enabled only on the master. When interrupt is asserted read the master first
and then the slave. Read the same number of items from both devices.
Refer to the GPIO Configuration for details.

GPIO_ GPIO
COMMENT
CTRL [3:0] FUNCTION
GPIO1 is active if any of the LEDCn[3:0] states A, B, or C are enabled in the exposure se-
Tristate or
0000 quence. If LEDCn[3:0] state A, B, or C is not enabled in the exposure sequence, GPIO1 is in
Mux Control
three strate unless externally pulled up.
GPIO1 is defined as a sample trigger input (slave). This input can come from an external
Input
0010 source or from another MAXM86161 in master sample mode. Exposure timing is controlled
Sample Trigger
by an internal oscillator.
GPIO1 is defined as an exposure trigger input (slave). This input can come from an external
Input
0110 source or from another MAXM86161 in master sample mode. Both sample and exposure
Exposure Trigger
timing is controlled by the GPIO1 input.
Input
GPIO1 is defined as a start of sample sync input. The falling edge of GPIO1 causes the
1001 HW_FORCE_
present sample sequence to be terminated.
SYNC
GPIO1 is defined as start of powerup sequence for one sample. The falling edge of GPIO1
Input
starts the powerup sequence followed by the exposure sequence as programmed in the
1010 Sample Sync
LEDCn[3:0] registers. After the sample data is pushed to the FIFO, the device fully shuts
ONE_SHOT
down and waits for the next Sample Sync pulse on GPIO1.

www.maximintegrated.com Maxim Integrated │  46

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

PPG CONFIGURATION 1 (0X11)

BIT 7 6 5 4 3 2 1 0
ALC_DIS- ADD_OFF-
Field – PPG1_ADC_RGE[1:0] PPG_TINT[1:0]
ABLE SET
Reset 0x0 0 0x0 0x0 0x3
Access Type Write, Read Write, Read Write, Read Write, Read Write, Read

ALC_DISABLE

VALUE ENUMERATION DECODE

0 OFF ALC is enabled
1 ON ALC is disabled

ADD_OFFSET
ADD_OFFSET is an option designed for dark current measurement. Adding offset to the PPG Data allows the dark
current measurement without clipping the signal below 0.
When ADD_OFFSET is set to 1, an offset is added to the PPG Data to be able to measure the dark current. The offset
is 8192 counts if PPG_SR is programmed for single pulse mode. The offset is 4096 counts if PPG_SR is programmed
for dual pulse mode.

PPG2_PPG1_ADC_RGE
These bits set the ADC range of the SPO2 sensor as shown in the table below.

PPG_PPG1_ADC_RGE[1:0] LSB (pA) FULL SCALE (nA)

00 7,8125 4096
01 15.625 8192
10 31.25 16384
11 62.5 32768

PPG1_PPG1_ADC_RGE
These bits set the ADC range of the SPO2 sensor as shown in the table below.

PPG_PPG1_ADC_RGE[1:0] LSB (pA) FULL SCALE (nA)

00 7,8125 4096
01 15.625 8192
10 31.25 16384
11 62.5 32768

www.maximintegrated.com Maxim Integrated │  47

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

PPG_TINT
These bits set the pulse width of the LED drivers and the integration time of PPG ADC as shown in the table below.
tPW = tTINT + tLED_SETLNG + 0.5μs

PPG_TINT[1:0] TPW, PULSE WIDTH (μs) TTINT, INTEGRATION TIME (μs) RESOLUTION BITS
00 21.3 14.8 19
01 35.9 29.4 19
10 65.2 58.7 19
11 123.8 117.3 19

PPG CONFIGURATION 2 (0X12)

BIT 7 6 5 4 3 2 1 0
Field PPG_SR[4:0] SMP_AVE[2:0]
Reset 0x11 0x0
Access Type Write, Read Write, Read

PPG_SR
These bits set the effective sampling rate of the PPG sensor as shown in the table below. The default on-chip sampling
clock frequency is 32768Hz.
Note: If a sample rate is set that cannot be supported by the selected pulse width and number of exposures per
sample, then the highest available sample rate is automatically set. The user can read back this register to confirm the
sample rate.

SAMPLING CLOCK FREQUENCY 32768Hz 32000Hz

PPG_SR[4:0] Samples per Second Samples per Second Pulses Per Sample, N
0x00 24.995 24.409 1
0x01 50.027 48.855 1
0x02 84.021 82.051 1
0x03 99.902 97.561 1
0x04 199,805 195.122 1
0x05 399.610 390.244 1
0x06 24.995 24.409 2
0x07 50.027 48.855 2
0x08 84.021 82.051 2
0x09 99.902 97.561 2
0x0A 8.000 7.8125 1
0x0B 16.000 15.625 1
0x0C 32.000 31.250 1
0x0D 64.000 62.500 1
0x0E 128.000 125.000 1

www.maximintegrated.com Maxim Integrated │  48

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

SAMPLING CLOCK FREQUENCY 32768Hz 32000Hz

0x0F 256.000 250.000 1
0x10 512.000 500.000 1
0x11 1024.000 1000.000 1
0x12 2048.000 2000.000 1
0x13 4096.000 4000.000 1
0x14-1F Reserved Reserved Reserved

Maximum Sample rates (sps) supported for all the Integration Time (PPG_TINT) and Number of Exposures:

NUMBER OF EXPO- PPG_TINT = 3

PPG_TINT = 0 (14.8μs) PPG_TINT = 1 (29.4μs) PPG_TINT = 2 (58.7μs)
SURE PER SAMPLE (117.3μs)
1 Exposure, N=1 4096 2048 2048 1024
2 Exposures, N=1 2048 1024 1024 512
3 Exposures, N=1 1024 1024 512 512
4 Exposures, N=1 1024 512 512 400
5 Exposures, N=1 512 512 512 256
6 Exposures, N=1 512 512 400 256
1 Exposure, N=2 100 100 100 100
2 Exposures, N=2 100 84 84 84
3 Exposures, N=2 50 50 50 50
4 Exposures, N=2 25 25 25 25
5 Exposures, N=2 25 25 25 25
6 Exposures, N=2 25 25 25 25

SMP_AVE
To reduce the amount of data throughput, adjacent samples (in each individual channel) can be averaged and deci-
mated on the chip by setting this register.
These bits set the number of samples that are averaged on chip before being written to the FIFO.

SMP_AVE[2:0] SAMPLE AVERAGE

000 1 (no averaging)
001 2
010 4
011 8
100 16
101 32
110 64
111 128

www.maximintegrated.com Maxim Integrated │  49

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

When BURST_EN is 1, SMP_AVE defines the number of conversions per burst. Depending on the BURST_RATE
programmed and the PPG_SR used, it might not be possible to accommodate some of SMP_AVE values. In that case,
SMP_AVE takes the highest value that can be accommodated. If SMP_AVE = 0 cannot be accommodated, burst mode
is disabled.
Note: PPG_SR itself depends on Number of conversions per sample (LEDC1 to LEDC6) and the LED Integration time
(PPG_TINT).
The following table shows the maximum SMP_AVE allowed for various configurations of BURST_RATE and PPG_SR:

BURST_RATE = 0 BURST_RATE = 1 BURST_RATE = 2 BURST_RATE = 3

PPG_SR USED
(8Hz) (32Hz) (84Hz) (256Hz)
0 (25Hz, N = 1) 1 DIS DIS DIS
1 (50Hz, N = 1) 2 0 DIS DIS
2 (84Hz, N = 1) 3 1 DIS DIS
3 (100Hz, N = 1) 3 1 DIS DIS
4 (200Hz, N = 1) 4 2 0 DIS
5 (400Hz, N = 1) 5 3 1 DIS
6 (25Hz, N = 2) 1 DIS DIS DIS
7 (50Hz, N = 2) 2 0 DIS DIS
8 (84Hz, N = 2) 3 1 DIS DIS
9 (100Hz, N = 2) 3 1 DIS DIS
A (8Hz, N = 1) DIS DIS DIS DIS
B (16Hz, N = 1) 0 DIS DIS DIS
C (32Hz, N = 1) 1 DIS DIS DIS
D (64Hz, N = 1) 2 0 DIS DIS
E (128Hz, N = 1) 3 1 0 DIS
F (256Hz, N = 1) 4 2 1 DIS
10 (512Hz, N = 1) 5 3 2 DIS
11 (1024Hz, N = 1) 6 4 3 0
12 (2048Hz, N = 1) 7 5 4 1
13 (4096Hz, N = 1) 7 6 5 2

PPG CONFIGURATION 3 (0X13)

BIT 7 6 5 4 3 2 1 0
DIG_FILT_
Field LED_SETLNG[1:0] – – BURST_RATE[1:0] BURST_EN
SEL
Reset 0x1 0x0 – – 0x0 0x0
Access Type Write, Read Write, Read – – Write, Read Write, Read

www.maximintegrated.com Maxim Integrated │  50

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

LED_SETLNG
Delay from rising edge of LED to start of ADC integration. This allows for the LED current to settle before the start of
ADC integration.

TLED_SETLNG, LED_SETLNG[1:0] DELAY (μs)

00 4.0
01 6.0 (default)
10 8.0
11 12.0

DIG_FILT_SEL
Select Digital Filter Type

VALUE ENUMERATION DECODE

0x0 Use CDM
0x1 Use FDM

BURST_RATE

VALUE ENUMERATION DECODE

0x0 8 Hz
0x1 32 Hz
0x2 84 Hz
0x3 256 Hz

BURST_EN
When Burst Mode is disabled, PPG data conversions are continuous at the sample rate defined by PPG_SR register,
When Burst mode is enabled, a burst of PPG data conversions occur at the sample rate defined by PPG_SR register.
Number of conversion in the burst is defined by the SMP_AVE register. Average data from the burst of data conversions
is pushed to the FIFO. The burst repeats at the rate defined in BURST_RATE[2:0] register. If the number of conversions
cannot be accommodated, the device uses the next highest number of conversions.
If the effective PPG_SR is too slow to accommodate the burst rate programmed, BURST_EN is automatically set to 0,
and the device runs in continuous mode.
Each data conversion cycle is a sequence of conversions defined in the LEDC1 to LEDC6 registers.

VALUE ENUMERATION DECODE

0x0 Disable Burst Conversion mode
0x1 Enable Burst Conversion Mode

www.maximintegrated.com Maxim Integrated │  51

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

PROX INTERRUPT THRESHOLD (0X14)

BIT 7 6 5 4 3 2 1 0
Field PROX_INT_THRESH[7:0]
Reset 0x00
Access Type Write, Read

PROX_INT_THRESH
This register sets the LED1 ADC count that triggers the transition between proximity mode and normal mode. The thresh-
old is defined as the 8 MSB bits of the ADC count. For example, if PROX_INT_THRESH[7:0] = 0x01, then an ADC value
of 2048 (decimal) or higher triggers the PROX interrupt. If PROX_INT_THRESH[7:0] = 0xFF, then only a saturated ADC
triggers the interrupt.
Please see the Proximity Mode Function section in the detailed description for more details on the operation of proximity
mode.
PHOTO DIODE BIAS (0X15)
BIT 7 6 5 4 3 2 1 0
Field – PDBIAS2[2:0] – PDBIAS1[2:0]
Reset – 0x0 – 0x0
Access Type – Write, Read – Write, Read

PDBIAS2
See the Photo Diode Biasing for more information.

PDBIAS2[2:0] PHOTO DIODE CAPACITANCE

0x001 0pF to 65pF
0x101 65pF to 130pF
0x110 130pF to 260pF
0x111 260pF to 520pF
All other values Not recommended

PDBIAS1
See the Photo Diode Biasing for more information.

PDBIAS1[2:0] PHOTO DIODE CAPACITANCE

0x001 0pF to 65pF
0x101 65pF to 130pF
0x110 130pF to 260pF
0x111 260pF to 520pF
All other values Not recommended

www.maximintegrated.com Maxim Integrated │  52

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

PICKET FENCE (0X16)

BIT 7 6 5 4 3 2 1 0
PF_EN- THRESHOLD_SIGMA_
Field PF_ORDER IIR_TC[1:0] IIR_INIT_VALUE[1:0]
ABLE MULT[1:0]
Reset 0x0 0x1 0x00 0x00 0x00
Access Type Write, Read Write, Read Write, Read Write, Read Write, Read

PF_ENABLE
Refer to the Picket Fence Detect-and-Replace Function for details.
PF_ENABLE set to 1 enabled the picket-fence detect and replace method.

VALUE ENUMERATION DECODE

0 OFF Disable (default)
1 ON Enable Detect and Replace

PF_ORDER
PF_ORDER determines which prediction method is used: the last sample or a linear fit to the previous four samples.
Refer to the Picket Fence Detect-and-Replace Function for details.

VALUE ENUMERATION DECODE

0 OFF Last Sample (1 point)
1 ON Fit 4 points to a line for prediction (default)

IIR_TC
IIR_TC[1:0] determines the IIR filter bandwidth where the lowest setting has the narrowest bandwidth of a first-order
filter.
Refer to Picket Fence Detect-and-Replace Function for details.

IIR_TC[1:0] COEFFICIENT SAMPLES TO 90%

00 1/64 146
01 1/32 72
10 1/16 35
11 1/8 17

IIR_INIT_VALUE
This IIR filter estimates the true standard deviation between the actual and predicted sample and tracks the ADC
Range setting.
Refer to the Picket Fence Detect-and-Replace Function for details.

IIR_INIT_VALUE[1:0] CODE
00 64
01 48
10 32
11 24

www.maximintegrated.com Maxim Integrated │  53

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

THRESHOLD_SIGMA_MULT
GAIN resulting from the SIGMA_MULT[1:0] setting determines the number of standard deviations of the delta between
the actual and predicted sample beyond which a picket-fence event is triggered.
Refer to the Picket Fence Detect-and-Replace Function for details.

THRESHOLD_SIGMA_MULT[1:0] GAIN
00 4
01 8
10 16
11 32

LED SEQUENCE REGISTER 1 (0X20)

BIT 7 6 5 4 3 2 1 0
Field LEDC2[3:0] LEDC1[3:0]
Reset 0x0 0x0
Access Type Write, Read Write, Read

LEDC2
These bits set the data type for LED Sequence 2 of the FIFO.
See the FIFO Configuration for more information.
LEDC1
These bits set the data type for LED Sequence 1 of the FIFO.
See the FIFO Configuration for more information.
LED SEQUENCE REGISTER 2 (0X21)
BIT 7 6 5 4 3 2 1 0
Field LEDC4[3:0] LEDC3[3:0]
Reset 0x0 0x0
Access Type Write, Read Write, Read

LEDC4
These bits set the data type for LED Sequence 4 of the FIFO.
See the FIFO Configuration for more information.
LEDC3
These bits set the data type for LED Sequence 3 of the FIFO.
See the FIFO Configuration for more information.
LED SEQUENCE REGISTER 3 (0X22)
BIT 7 6 5 4 3 2 1 0
Field LEDC6[3:0] LEDC5[3:0]
Reset 0x0 0x0
Access Type Write, Read Write, Read

www.maximintegrated.com Maxim Integrated │  54

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

LEDC6
These bits set the data type for LED Sequence 6 of the FIFO.
See the FIFO Configuration for more information.
LEDC5
These bits set the data type for LED Sequence 5 of the FIFO.
See the FIFO Configuration for more information.
LED1 PA (0x23)
BIT 7 6 5 4 3 2 1 0
Field LED1_DRV[7:0]
Reset 0x00
Access Type Write, Read

LED1_DRV
These bits set the nominal drive current of LED 1 as shown in the table below.

LEDX_RGE[1:0] 00 01 10 11
LEDx_PA[7:0] LED Current (mA) LED Current (mA) LED Current (mA) LED Current (mA)
00000000 0.00 0.00 0.00 0.00
00000001 0.12 0.24 0.36 0.48
00000010 0.24 0.48 0.73 0.97
00000011 0.36 0.73 1.09 1.45
............
11111100 30.6 61.3 91.9 122.5
11111101 30.8 61.5 92.3 123.0
11111110 30.9 61.8 92.6 123.5
11111111 31.0 62.0 93.0 124.0
LSB 0.12 0.24 0.36 0.48

LED2 PA (0x24)
BIT 7 6 5 4 3 2 1 0
Field LED2_DRV[7:0]
Reset 0x00
Access Type Write, Read

www.maximintegrated.com Maxim Integrated │  55

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

LED2_DRV
These bits set the nominal drive current of of LED 2. See LED1_DRV for description.
LED3_PA (0x25)
BIT 7 6 5 4 3 2 1 0
Field LED3_DRV[7:0]
Reset 0x00
Access Type Write, Read

LED3_DRV
These bits set the nominal drive current of of LED 2. See LED1_DRV for description.

LED PILOT PA (0x29)

BIT 7 6 5 4 3 2 1 0
Field PILOT_PA[7:0]
Reset 0x00
Access Type Write, Read

PILOT_PA
The purpose of PILOT_PA[7:0] is to set the LED power during the PROX mode, as well as in Multi-LED mode. These
bits set the nominal drive current for the pilot mode as shown in the table below.
When LEDx is used, the respective LEDx_RGE[1:0] is used to control the range of the LED driver in conjunction with
PILOT_PA[7:0]. For instance, if LED1 is used in the PILOT mode, then, LED1_RGE[1:0] together with PILOT_PA[7:0]
will be used to set the LED1 current.

LEDX_RGE[1:0] 00 01 10 11
PILOT_PA[7:0] LED Current (mA) LED Current (mA) LED Current (mA) LED Current (mA)
00000000 0.00 0.00 0.00 0.00
00000001 0.12 0.24 0.36 0.48
00000010 0.24 0.48 0.73 0.97
00000011 0.36 0.73 1.09 1.45
............
11111100 30.6 61.3 91.9 122.5
11111101 30.8 61.5 92.3 123.0
11111110 30.9 61.8 92.6 123.5
11111111 31.0 62.0 93.0 124.0
LSB 0.12 0.24 0.36 0.48

www.maximintegrated.com Maxim Integrated │  56

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

LED RANGE 1 (0X2A)

BIT 7 6 5 4 3 2 1 0
Field – – LED3_RGE[1:0] LED2_RGE[1:0] LED1_RGE[1:0]
Reset – – 0x00 0x00 0x00
Access Type – – Write, Read Write, Read Write, Read

LED3_RGE
Range selection of the LED current. Please refer to LED1_PA[7:0] for more details.
LEDX_RGE[1:0]
LED CURRENT(mA)
(X = 1 TO 6)
00 31
01 62
10 93
11 124

LED2_RGE
Range selection of the LED current. Please refer to LED3_RGE[1:0] for more details.
LED1_RGE
Range selection of the LED current. Please refer to LED3_RGE[1:0] for more details.

S1 HI RES DAC1 (0x2C)

BIT 7 6 5 4 3 2 1 0
S1_HRES_
Field – S1_HRES_DAC1[5:0]
DAC1_OVR
Reset 0x0 – 0x00
Access Type Write, Read – Write, Read

S1_HRES_DAC1_OVR

VALUE ENUMERATION DECODE

0 OFF The high resolution DAC for PPG1 is controlled by the chip.
This allows the high resolution DAC for PPG1 used in exposure 1 to be controlled by the soft-
1 ON
ware.

S1_HRES_DAC1
If S1_ HI_RES_DAC1_OVR = 1, then bits S1_HRES_DAC1[5:0] set the high-resolution DAC code used in PPG1 ADC.
This allows the algorithm to control ADC subranging.
If S1_ HI_RES_DAC1_OVR = 0, then bits S1_HRES_DAC1[5:0] have no effect on the PPG1 ADC.
S2 HI RES DAC1 (0x2D)
BIT 7 6 5 4 3 2 1 0
S2_HRES_
Field – S2_HRES_DAC1[5:0]
DAC1_OVR
Reset 0x0 – 0x00
Access Type Write, Read – Write, Read

www.maximintegrated.com Maxim Integrated │  57

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

S2_HRES_DAC1_OVR

VALUE ENUMERATION DECODE

0 OFF The high resolution DAC for PPG1 is controlled by the chip.
This allows the high resolution DAC for PPG1 used in exposure 2 to be controlled by the soft-
1 ON
ware.

S2_HRES_DAC1
If S2_ HI_RES_DAC1_OVR = 1, then bits S2_HRES_DAC1[5:0] set the high resolution DAC code used in PPG1 ADC.
This allows the algorithm to control ADC subranging
If S2_ HI_RES_DAC1_OVR = 0, then bits S2_HRES_DAC1[5:0] have no effect on the PPG1 ADC
S3 HI RES DAC1 (0x2E)
BIT 7 6 5 4 3 2 1 0
S3_HRES_
Field – S3_HRES_DAC1[5:0]
DAC1_OVR
Reset 0x0 – 0x0
Access Type Write, Read – Write, Read

S2_HRES_DAC1_OVR

VALUE ENUMERATION DECODE

0x0 OFF The high resolution DAC for PPG1 is controlled by the chip.
This allows the high resolution DAC for PPG1 used in exposure 3 to be controlled by the
0x1 ON
software.

S3_HRES_DAC1
If S3_ HI_RES_DAC1_OVR = 1, then bits S3_HRES_DAC1[5:0] set the high resolution DAC code used in PPG1 ADC.
This allows the algorithm to control ADC subranging.
If S3_ HI_RES_DAC1_OVR = 0, then bits S3_HRES_DAC1[5:0] have no effect on the PPG1 ADC.
S4 HI RES DAC1 (0x2F)
BIT 7 6 5 4 3 2 1 0
S4_HRES_
Field – S4_HRES_DAC1[5:0]
DAC1_OVR
Reset 0b0 – 0x0
Access Type Write, Read – Write, Read

S4_HRES_DAC1_OVR

VALUE ENUMERATION DECODE

0x0 OFF The high resolution DAC for PPG1 is controlled by the chip.
This allows the high resolution DAC for PPG1 used in exposure 4 to be controlled by the
0x1 ON
software.

www.maximintegrated.com Maxim Integrated │  58

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

S4_HRES_DAC1
If S4_ HI_RES_DAC1_OVR = 1, then bits S4_HRES_DAC1[5:0] set the high resolution DAC code used in PPG1 ADC.
This allows the algorithm to control ADC subranging
If S4_ HI_RES_DAC1_OVR = 0, then bits S4_HRES_DAC1[5:0] have no effect on the PPG1 ADC

S5 HI RES DAC1 (0x30)

BIT 7 6 5 4 3 2 1 0
S5_HRES_
Field – S5_HRES_DAC1[5:0]
DAC1_OVR
Reset 0b0 – 0x0
Access Type Write, Read – Write, Read

S5_HRES_DAC1_OVR

VALUE ENUMERATION DECODE

0x0 OFF The high resolution DAC for PPG1 is controlled by the chip.
This allows the high resolution DAC for PPG1 used in exposure 5 to be controlled by the
0x1 ON
software.

S5_HRES_DAC1
If S5_ HI_RES_DAC1_OVR = 1, then bits S5_HRES_DAC1[5:0] set the high resolution DAC code used in PPG1 ADC.
This allows the algorithm to control ADC subranging
If S5_ HI_RES_DAC1_OVR = 0, then bits S5_HRES_DAC1[5:0] have no effect on the PPG1 ADC

S6 HI RES DAC1 (0x31)

BIT 7 6 5 4 3 2 1 0
S6_HRES_
Field – S6_HRES_DAC1[5:0]
DAC1_OVR
Reset 0b0 – 0x0
Access Type Write, Read – Write, Read

S6_HRES_DAC1_OVR

VALUE ENUMERATION DECODE

0x0 OFF The high resolution DAC for PPG1 is controlled by the chip.
This allows the high resolution DAC for PPG1 used in exposure 6 to be controlled by the
0x1 ON
software.

www.maximintegrated.com Maxim Integrated │  59

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

S6_HRES_DAC1
If S6_ HI_RES_DAC1_OVR = 1, then bits S6_HRES_DAC1[5:0] set the high resolution DAC code used in PPG1 ADC.
This allows the algorithm to control ADC subranging
If S6_ HI_RES_DAC1_OVR = 0, then bits S6_HRES_DAC1[5:0] have no effect on the PPG1 ADC

DIE TEMPERATURE CONFIGURATION (0X40)

BIT 7 6 5 4 3 2 1 0
Field – – – – – – – TEMP_EN
Reset – – – – – – – 0x0
Access Type – – – – – – – Write, Read

TEMP_EN
The bit gets cleared after temperature measurement completes.

VALUE ENUMERATION DECODE

0x0 Idle
0x1 Start one temperature measurement

DIE TEMPERATURE INTEGER (0X41)

BIT 7 6 5 4 3 2 1 0
Field TEMP_INT[7:0]
Reset 0x0
Access Type Read Only

TEMP_INT
This register stores the integer temperature data in 2s compliment form. For example, 0x00 = 0°C (typ), 0x7F = 127°C
(typ) and 0x80 = -128°C (typ)
Note: TEMP_INT and TEMP_FRAC registers should be read using the Serial Interface in burst mode to ensure that they
belong to the same sample.
DIE TEMPERATURE FRACTION (0X42)
BIT 7 6 5 4 3 2 1 0
Field – – – – TEMP_FRAC[3:0]
Reset – – – – 0x0
Access Type – – – – Read Only

www.maximintegrated.com Maxim Integrated │  60

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

TEMP_FRAC
This register store the fractional temperature data in increments of 0.0625°C. 0x1 = 0.0625°C and 0xF = 0.9375°C.
Note: TINT and TFRAC registers should be read using the Serial Interface in burst mode to ensure that they belong to
the same sample.

DAC CALIBRATION ENABLE (0X50)

BIT 7 6 5 4 3 2 1 0
CAL_DAC_ CAL_ CAL_ START_
Field – – – –
Complete DAC2_OOR DAC1_OOR CAL
Reset – 0b0 0b0 0b0 – 00 – –
Access Type – Read Only Read Only Read Only – Write, Read – –

CAL_DAC_Complete
High after DAC Calibration completes. It gets reset when calibration is restarted using the START_CAL bit

VALUE ENUMERATION DECODE

0x0 Calibration not complete or reset.
0x1 Calibration complete.

CAL_DAC2_OOR
High if any DAC2 Calibration Coefficient is out of range (OOR)

VALUE ENUMERATION DECODE

0x0 In Range
0x1 Any DAC2 Coefficient is out of range (OOR)

CAL_DAC1_OOR
High if any DAC1 Calibration Coefficient is out of range (OOR)

VALUE ENUMERATION DECODE

0x0 In Range
0x1 Any DAC1 Coefficient is out of range (OOR)

START_CAL
Start DAC1 and DAC2 calibration. This bit clears after calibration.
SHA COMMAND (0XF0)
BIT 7 6 5 4 3 2 1 0
Field SHA_CMD[7:0]
Reset 0x0
Access Type Write, Read

www.maximintegrated.com Maxim Integrated │  61

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

SHA_CMD

VALUE ENUMERATION DECODE

0x35 MAC with ROM ID
0x36 MAC without ROM ID
Others Reserved

SHA CONFIGURATION (0XF1)

BIT 7 6 5 4 3 2 1 0
SHA_
Field – – – – – – SHA_EN
START
Reset – – – – – – 0x0 0x0
Access Type – – – – – – Write, Read Write, Read

SHA_EN
Authentication is performed using a FIPS 180-3 compliant SHA-256 one-way hash algorithm on a 512-bit message block.
The message block consists of a 160-bit secret, a 160-bit challenge, and 192 bits of constant data. Optionally, the 64-bit
ROM ID replaces 64 of the 192 bits of constant data used in the hash operation. 16 bits out of the 160-bit secret and 16
bits of ROM ID are programmable - 8 bits each in metal and 8 bits each in OTP bits.
The host and the MAXM86161 both calculate the result based on a mutually known secret. The result of the hash opera-
tion is known as the message authentication code (MAC) or message digest. The MAC is returned by the MAXM86161
for comparison with the host’s MAC. Note that the secret is never transmitted on the bus; thus, it cannot be captured by
observing bus traffic. Each authentication attempt is initiated by the host system by writing a 160-bit random challenge
into the SHA memory address space 0x00h to 0x09h. The host then issues the compute MAC or compute MAC with
ROM ID command. The MAC is computed per FIPS 180-3, and stored in address space 0x00h to 0x0Fh overwriting the
challenge value.
Note that the results of the authentication attempt are determined by host verification. Operation of the MAXM86161 is
not affected by authentication success or failure.
Sequence of operation is as follows:
1) Enable SHA_DONE Interrupt
2) Enable SHA_EN bit
3) Write 160 bit random challenge value to RAM using registers MEM_IDX and MEM_DATA.
4) Write command, with ROM ID (0x35) or without ROM ID (0x36) to SHA_CMD register.
5) Write 1 to SHA_START and 1 to SHA_EN bit.
6) Wait for SHA_DONE interrupt.
7) Read 256 MAC value from RAM using registers MEM_IDX and MEM_DATA.
8) Compare MAC from MAXM86161 wth Host’s precalculated MAC.
9) Check PASS or FAIL
10) Disable SHA_EN bit (Write 0 to SHA_EN bit).

www.maximintegrated.com Maxim Integrated │  62

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

VALUE ENUMERATION DECODE

0x0 Authentication is disabled
0x1 Authentication is enabled

SHA_START
The bit gets cleared after authentication completes. The valid command (0x35 or 0x36) should be written to the SHA_
CMD register and challenge value should be written to the RAM by Host before writing 1 to this bit.
MEMORY CONTROL (0XF2)
BIT 7 6 5 4 3 2 1 0
MEM_WR_
Field – – – – – – BANK_SEL
EN
Reset – – – – – – 0x0 0x0
Access Type – – – – – – Write, Read Write, Read

MEM_WR_EN
Enable write access to Memory via.

VALUE ENUMERATION DECODE

0x0 Writing to Memory via is disabled.
0x1 Writing to Memory via is enabled

BANK_SEL
Selects the memory bank for reading and writing.
Burst reading or writing the memory past 0xFF automatically increments BANK_SEL to 1.

VALUE ENUMERATION DECODE

0x0 Select Bank 0, address 0x00 to 0xFF
0x1 Select Bank 1, address 0x100 to 0x17f

MEMORY INDEX (0XF3)

BIT 7 6 5 4 3 2 1 0
Field MEM_IDX[7:0]
Reset 0x0
Access Type Write, Read

www.maximintegrated.com Maxim Integrated │  63

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

MEM_IDX
Index to Memory for reading and writing. The Memory is 384 bytes, and is divided into two banks: Bank 0 from 0x00 to
0xFF and Bank 1 from 0x100 to 0x17F. The bank is selected by the BANK_SEL register bit. MEM_IDX is the starting
address for burst writing to or reading from memory. Burst accessing the memory past 0xFF accesses Bank 1. The
memory address saturates at 0x17F.
MEMORY DATA (0XF4)
BIT 7 6 5 4 3 2 1 0
Field MEM_DATA[7:0]
Reset 0x0
Access Type Write, Read, Dual

MEM_DATA
Data to be written or Data read from Memory
Reading this register does not automatically increment the register address. So burst reading this register reads the
same register over and over, but the address to the Memory autoincrements until BANK_SEL becomes 1 and MEM_IDX
becomes 0x7F.

PART ID (0XFF)
BIT 7 6 5 4 3 2 1 0
Field PART_ID[7:0]
Reset 0x36
Access Type Read Only

PART_ID
This register stores the Part identifier for the chip.
0x36

www.maximintegrated.com Maxim Integrated │  64

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Ordering Information
PART NUMBER TEMP RANGE PIN-PACKAGE
MAXM86161EFD+ -40°C to +85°C 4.3mm x 2.9mm x 1.4mm 14-Pin OLGA
MAXM86161EFD+T -40°C to +85°C 4.3mm x 2.9mm x 1.4mm 14-Pin OLGA
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.

www.maximintegrated.com Maxim Integrated │  65

MAXM86161 Single-Supply Integrated Optical Module
for HR and SpO2 Measurement

Revision History
REVISION REVISION PAGES
DESCRIPTION
NUMBER DATE CHANGED
0 3/19 Initial release —

For pricing, delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html.

Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.

Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. © 2019 Maxim Integrated Products, Inc. │  66
Mouser Electronics

Authorized Distributor

Click to View Pricing, Inventory, Delivery & Lifecycle Information:

Maxim Integrated:
MAXM86161EFD+