Si 4844- B20

B R O A D C AST A NALOG T UNING D IGITAL D ISPLAY

A M /FM /S W R ADIO R E CEIVER
Features
 Worldwide FM band support  Bass/Treble support
(64–109 MHz)  Minimal BOM components with no
 Worldwide AM band support manual alignment
(504–1750 kHz)  Excellent real-world performance
 SW band support  China TV channels audio carrier
(2.3–28.5 MHz) reception in FM band
 Selectable support for all AM/FM  EN55020 compliant
regional bands  Two AAA batteries with 2.0 to 3.6 V
 Enhance FM/SW band coverage supply voltage
2-wire control interface Ordering Information:
  Wide range of ferrite loop sticks and
See page 21.
 Mono/Stereo and valid station air loop antenna support
indicator  24-pin SSOP package
 Digital volume support  RoHS compliant
Pin Assignments

Applications
Si4844-B20 (SSOP)
 Table and portable radios  Modules for consumer electronics
 Stereos  Entertainment systems LNA_EN 1 24 LOUT
 Mini/micro systems  Toys, lamps, and any application IRQ 2 23 ROUT
 Boom boxes needing an AM/FM/SW radio TUNE1 3 22 DBYP
 Clock radios  Mini HiFi TUNE2 4 21 VDD2
 iPhone docking BAND 5 20 VDD1
NC 6 19 XTALI
Description NC 7 18 XTALO
FMI 8 17 SCLK
The Si4844-B is the analog-tuned digital-display digital CMOS AM/FM/SW radio RFGND 9 16 SDIO
receiver IC that integrates the complete receiver function from antenna input to audio NC 10 15 RST
output. Working with the host MCU (I2C-compatible 2-wire control interface),
NC 11 14 GND
frequencies and stereo/mono information can be displayed on LCD while the analog-
AMI 12 13 GND
tune features are kept. Si4844-B is pin-to-pin compatible with the current Si484x-A
tuner. Sharing all the advanced features of the Si484x-A, Si4844-B can support a wider
range of FM and SW bands. The Si4844-B also supports China TV channels audio This product, its features, and/or its
reception in FM band. The superior control algorithm integrated in the Si4844-B architecture is covered by one or more of
provides a easy and reliable control interface while eliminating all the manual-tuned the following patents, as well as other
external components used in a traditional solution.
patents, pending and issued, both
foreign and domestic: 7,127,217;
Functional Block Diagram 7,272,373; 7,272,375; 7,321,324;
7,355,476; 7,426,376; 7,471,940;
Si4844-B
Si4830/34 7,339,503; 7,339,504.
AMI ADC DAC LOUT
AM
RFGND LNA DSP
ANT
ADC DAC ROUT
FM
ANT AGC
FMI
0/90
TUNE1/2

ADC
XTALI AFC CONTROL INTERFACE BAND

2.0~3.6V VDD1/2
XTAL
REG
OSC
SCLK
IRQ

SDIO
RST

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Si 4844- B2 0

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 Si4844-B20
TA B L E OF C ONTENTS

Section Page
1. Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Typical Application Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3. Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4. Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.2. FM Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.3. AM Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.4. SW Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.5. Frequency Tuning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.6. Band Select . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.7. Bass and Treble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
4.8. Volume Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.9. Stereo Audio Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.10. Stereo DAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.11. Soft Mute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
4.12. Reference Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.13. Reset, Powerup, and Powerdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.14. Memorizing Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.15. Programming with Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5. Commands and Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6. Pin Description: Si4844-B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7. Ordering Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
8. Package Outline: Si4844-B20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
9. PCB Land Pattern: Si4844-B20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
10. Top Marking: Si4844-B20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
11. Additional Reference Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Document Change List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

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Si 4844- B2 0
1. Electrical Specifications

Table 1. Recommended Operating Conditions1,2

Parameter Symbol Test Condition Min Typ Max Unit

Supply Voltage3 VDD 2 — 3.6 V

Power Supply Powerup Rise Time VDDRISE 10 — — µs

Notes:
1. Typical values in the data sheet apply at VDD = 3.3 V and 25 °C unless otherwise stated.
2. All minimum and maximum specifications in the data sheet apply across the recommended operating conditions for
minimum VDD = 2.7 V.
3. Operation at minimum VDD is guaranteed by characterization when VDD voltage is ramped down to 2.0 V. Part
initialization may become unresponsive below 2.3 V.

Table 2. DC Characteristics
(VDD = 2.7 to 3.6 V, TA = –15 to 85 °C)

Parameter Symbol Test Condition Min Typ Max Unit

FM Mode
Supply Current1 IFM — 21.0 — mA

Supply Current2 IFM Low SNR level — 21.5 — mA

AM/SW Mode
Supply Current1 IAM — 20.0 — mA

Supplies and Interface

VDD Powerdown IDDPD — 10 — µA
Current
Notes:
1. Specifications are guaranteed by characterization.
2. LNA is automatically switched to higher current mode for optimum sensitivity in weak signal conditions.

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 Si4844-B20

Table 3. Reset Timing Characteristics

(VDD = 2.7 to 3.6 V, TA = –15 to 85 °C)

Parameter Symbol Min Typ Max Unit

RSTB Pulse Width tPRST 100 — — µs

2-wire bus idle time after RSTB rises tSDIO 100 — — µs

2-wire bus idle time before RSTB rises, and VDD valid time tSRST 100 — — µs
before RSTB rises
RSTB low time before VDD becomes invalid tRRST 0 — — µs

Notes:
1. RSTB must be held low for at least 100 µs after the voltage supply has been ramped up.
2. RSTB needs to be asserted (pulled low) prior to the supply voltage being ramped down.

tSRST tPRST
VDD tRRST
tSDIO tSDIO

RSTB

SCLK

Normal Normal
POWER_UP POWER_UP
Operation Operation
SDIO

Figure 1. Reset Timing

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Table 4. 2-Wire Control Interface Characteristics1,2,3

(VDD = 2.7 to 3.6 V, TA = –15 to 85 °C)

Parameter Symbol Test Condition Min Typ Max Unit

SCLK Frequency fSCLK 0 — 400 kHz

SCLK Low Time tLOW 1.3 — — µs

SCLK High Time tHIGH 0.6 — — µs

SCLK Input to SDIO  Setup (START) tSU:STA 0.6 — — µs

SCLK Input to SDIO  Hold (START) tHD:STA 0.6 — — µs

SDIO Input to SCLK  Setup tSU:DAT 100 — — ns

SDIO Input to SCLK  Hold4,5 tHD:DAT 0 — 900 ns

SCLK input to SDIO  Setup (STOP) tSU:STO 0.6 — — µs

STOP to START Time tBUF 1.3 — — µs

SDIO Output Fall Time tf:OUT — 250 ns

Cb
20 + 0.1 -----------
1pF

SDIO Input, SCLK Rise/Fall Time tf:IN — 300 ns

tr:IN Cb
20 + 0.1 -----------
1pF

SCLK, SDIO Capacitive Loading Cb — — 50 pF

Input Filter Pulse Suppression tSP — — 50 ns

Notes:
1. When VD = 0 V, SCLK and SDIO are low impedance.
2. When selecting 2-wire mode, the user must ensure that a 2-wire start condition (falling edge of SDIO while SCLK is
high) does not occur within 300 ns before the rising edge of RST.
3. When selecting 2-wire mode, the user must ensure that SCLK is high during the rising edge of RST, and stays high
until after the first start condition.
4. The Si484x delays SDIO by a minimum of 300 ns from the VIH threshold of SCLK to comply with the minimum tHD:DAT
specification.
5. The maximum tHD:DAT has only to be met when fSCLK = 400 kHz. At frequencies below 400 kHz, tHD:DAT may be
violated as long as all other timing parameters are met.

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 Si4844-B20

tSU:STA tHD:STA tLOW tHIGH tr:IN tf:IN tSP tSU:STO tBUF

70%
SCLK
30%

70%
SDIO
30%

START tHD:DAT tSU:DAT tf:IN,

tr:IN STOP START
tf:OUT

Figure 2. 2-Wire Control Interface Read and Write Timing Parameters

SCLK

A6-A0,
SDIO D7-D0 D7-D0
R/W

START ADDRESS + R/W ACK DATA ACK DATA ACK STOP

Figure 3. 2-Wire Control Interface Read and Write Timing Diagram

Table 5. FM Receiver Characteristics1,2

(VDD = 2.7 to 3.6 V, TA = –15 to 85 °C)

Parameter Symbol Test Condition Min Typ Max Unit

Input Frequency fRF 64 — 109 MHz

Sensitivity with Headphone Network3 (S+N)/N = 26 dB — 2.2 — µV EMF

Notes:
1. Additional testing information is available in “AN603: Si4822/26/27/40/44 DEMO Board Test Procedure.”
Volume = maximum for all tests. Tested at RF = 98.1 MHz.
2. To ensure proper operation and receiver performance, follow the guidelines in “AN602: Si4822/26/27/40/44 Antenna,
Schematic, Layout, and Design Guidelines.” Skyworks will evaluate schematics and layouts for qualified customers.
3. Frequency is 64~109 MHz.
4. Guaranteed by characterization.
5. VEMF = 1 mV.
6. FMOD = 1 kHz, MONO, and L = R unless noted otherwise.
7. f = 22.5 kHz.
8. |f2 – f1| > 2 MHz, f0 = 2 x f1 – f2.
9. BAF = 300 Hz to 15 kHz, A-weighted.
10. At LOUT and ROUT pins.
11. f = 75 kHz.
12. Tested in Digital Volume Mode.

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Si 4844- B2 0
Table 5. FM Receiver Characteristics1,2 (Continued)
(VDD = 2.7 to 3.6 V, TA = –15 to 85 °C)

Parameter Symbol Test Condition Min Typ Max Unit

LNA Input Resistance4,5 — 4 — k

LNA Input Capacitance4,5 — 5 — pF

AM Suppression4,5,6,7 m = 0.3 — 50 — dB

Input IP34,8 — 105 — dBµV EMF

Adjacent Channel Selectivity4 ±200 kHz — 50 — dB

Alternate Channel Selectivity4 ±400 kHz — 65 — dB

Audio Output Voltage5,6,7,12 — 80 — mVRMS

Audio Mono S/N5,6,7,9,10 — 55 — dB

Audio Stereo S/N3,4,5,7,9,10 — 55 — dB

Audio Frequency Response Low4 –3 dB — — 30 Hz

Audio Frequency Response High4 –3 dB 15 — — kHz

Audio Stereo Separation5,11 — 40 — dB

Audio THD5,6,11 — 0.1 0.5 %

Audio Output Load Resistance4,10 RL Single-ended 10 — — k

Audio Output Load Capacitance4,10 CL Single-ended — — 50 pF

Notes:
1. Additional testing information is available in “AN603: Si4822/26/27/40/44 DEMO Board Test Procedure.”
Volume = maximum for all tests. Tested at RF = 98.1 MHz.
2. To ensure proper operation and receiver performance, follow the guidelines in “AN602: Si4822/26/27/40/44 Antenna,
Schematic, Layout, and Design Guidelines.” Skyworks will evaluate schematics and layouts for qualified customers.
3. Frequency is 64~109 MHz.
4. Guaranteed by characterization.
5. VEMF = 1 mV.
6. FMOD = 1 kHz, MONO, and L = R unless noted otherwise.
7. f = 22.5 kHz.
8. |f2 – f1| > 2 MHz, f0 = 2 x f1 – f2.
9. BAF = 300 Hz to 15 kHz, A-weighted.
10. At LOUT and ROUT pins.
11. f = 75 kHz.
12. Tested in Digital Volume Mode.

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 Si4844-B20

Table 6. AM/SW Receiver Characteristics1, 2

(VDD = 2.7 to 3.6 V, TA = –15 to 85 °C)

Parameter Symbol Test Condition Min Typ Max Unit

Input Frequency fRF Medium Wave (AM) 504 — 1750 kHz

Short Wave (SW) 2.3 — 28.5 MHz

Sensitivity3,4,5 (S+N)/N = 26 dB — 30 — µV EMF

Large Signal Voltage Handling5 THD < 8% — 300 — mVRMS

Power Supply Rejection Ratio5 ΔVDD = 100 mVRMS, 100 Hz — 40 — dB

Audio Output Voltage3,6,8 — 60 — mVRMS

Audio S/N3,4,6 — 55 — dB

Audio THD3,6 — 0.1 0.5 %

Antenna Inductance5,7 180 — 450 µH

Notes:
1. Additional testing information is available in “AN603: Si4822/26/27/40/44 DEMO Board Test Procedure.”
Volume = maximum for all tests. Tested at RF = 520 kHz and RF = 6 MHz.
2. To ensure proper operation and receiver performance, follow the guidelines in ““AN602: Si4822/26/27/40/44 Antenna,
Schematic, Layout, and Design Guidelines.” Skyworks will evaluate schematics and layouts for qualified customers.
3. FMOD = 1 kHz, 30% modulation, 2 kHz channel filter.
4. BAF = 300 Hz to 15 kHz, A-weighted.
5. Guaranteed by characterization.
6. VIN = 5 mVrms.
7. Stray capacitance on antenna and board must be < 10 pF to achieve full tuning range at higher inductance levels.
8. Tested in Digital Volume Mode.

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Si 4844- B2 0

Table 7. Reference Clock and Crystal Characteristics

(VDD = 2.7 to 3.6 V, TA = –15 to 85 °C)

Parameter Symbol Test Condition Min Typ Max Unit

Reference Clock
XTALI Supported Reference Clock 31.130 32.768 40,000 kHz
Frequencies*
Reference Clock Frequency Tolerance for –100 — 100 ppm
XTALI
REFCLK_PRESCALE 1 4095
REFCLK 31.130 32.768 34.406 kHz

Crystal Oscillator
Crystal Oscillator Frequency — 32.768 — kHz
Crystal Frequency Tolerance –100 — 100 ppm
Board Capacitance — — 3.5 pF
*Note: The Si4844-B20 divides the RCLK input by REFCLK_PROSCALE to obtain REFCLK. There are some RCLK
frequencies between 31.130 kHz and 40 MHz that are not supported. For more details, see Table 9 of “AN610: Si48xx
ATDD Programming Guide.”

Table 8. Thermal Conditions

Parameter Symbol Min Typ Max Unit

Thermal Resistance* JA — 80 — °C/W

Ambient Temperature TA –15 25 85 °C

Junction Temperature TJ — — 92 °C

*Note: Thermal resistance assumes a multi-layer PCB with the exposed pad soldered to a topside PCB pad.

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 Si4844-B20

Table 9. Absolute Maximum Ratings 1, 2

Parameter Symbol Value Unit

Supply Voltage VDD –0.5 to 5.8 V

Input Current3 IIN 10 mA

Operating Temperature TOP –40 to 95 C

Storage Temperature TSTG –55 to 150 C
RF Input Level4 0.4 VPK

Notes:
1. Permanent device damage may occur if the above Absolute Maximum Ratings are exceeded. Functional operation
should be restricted to the conditions as specified in the operational sections of this data sheet. Exposure beyond
recommended operating conditions for extended periods may affect device reliability.
2. The Si4844-B devices are high-performance RF integrated circuits with certain pins having an ESD rating of < 2kV
HBM. Handling and assembly of these devices should only be done at ESD-protected workstations.
3. For input pins RST, SDIO, SCLK, XTALO, XTALI, BAND, TUNE2, TUNE1, IRQ, and LNA_EN.
4. At RF input pins, FMI, and AMI.

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Si 4844- B2 0
2. Typical Application Schematic

TUNE1

R1
203k 1%

SW

TUNE1
FMI

S1 R2

2.5k/100M
VR1 50k 1%
B1 100k BAND 1 2
3 AM
4
AM antenna

R3
ANT1

180k 1%
IRQ To host MCU
C5
AMI
FM
LNA_EN
0.47u 12

11

10

1
RFGND

BAND

LNA_EN
AMI

NC

NC

FMI

NC

NC

TUNE2

TUNE1

IRQ
R4
67k 1%

C5
U1
AMI
0.47u Optional
XTALO

XTALI

ROUT
VDD1

VDD2

LOUT
ANT2

DBYP
SDIO

SCLK
GND

GND

RST

RFGND
13

14

15

T1
16

17

18

19

20

21

22

23

24
LOUT
C4
Optional: AM air loop antenna ROUT
C1 0.1u
0.1u
VDD
2.0 TO 3.6V
VDD
2.0 TO 3.6V
RESET
SDIO
To host MCU
SCLK
Y1

32.768KHz

C3 C2
22p 22p

Optional

Notes:
1. Place C4 close to VDD2 and DBYP pins.
2. All grounds connect directly to GND plane on PCB.
3. Pin 6 and 7 leave floating.
4. To ensure proper operation and receiver performance, follow the guidelines in “AN602: Si4822/26/27/40/44 Antenna,
Schematic, Layout, and Design Guidelines.” Skyworks will evaluate the schematics and layouts for qualified customers.
5. Pin 8 connects to the FM antenna interface and pin 12 connects to the AM antenna interface.
6. Place Si484x as close as possible to antenna jack and keep the FMI and AMI traces as short as possible.
7. Recommend keeping the AM ferrite loop antenna at least 5 cm away from the Si4844-B.
8. Keep the AM ferrite loot antenna away from the MCU, audio amplifier, and other circuits which have AM interference.
9. Place the transformer T1 away from any sources of interference and even away from the I/O signals of the Si4844-B.

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 Si4844-B20
3. Bill of Materials

Table 10. Si4844-B20 Bill of Materials

Component(s) Value/Description Supplier
C1 Reset capacitor 0.1 µF, ±20%, Z5U/X7R Murata
C4 Supply bypass capacitor, 0.1 µF, ±20%, Z5U/X7R Murata
C5 Coupling capacitor, 0.47 µF, ±20%, Z5U/X7R Murata
B1 Ferrite bead 2.5 k/100 MHz Murata
VR1 Variable resistor (POT), 100 k, ±10% Kennon
U1 Si4844-B AM/FM/SW Analog Tune Digital Display Radio Tuner Skyworks
ANT1 Ferrite stick,180–450 μH Jiaxin
Optional Components
Crystal load capacitors, 22 pF, ±5%, COG
C2, C3 Venkel
(Optional: for crystal oscillator option)
Y1 32.768 kHz crystal (Optional: for crystal oscillator option) Epson or equivalent
ANT2 Air loop antenna, 10-20 μH various
S1 Band switch Any, depends on customer
R1 Resistor, 203 k, ±1% Venkel
R2 Resistor, 50 k, ±1% Venkel
R3 Resistor, 180 k, ±1% Venkel
R4 Resistor, 67 k, ±1% Venkel

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Si 4844- B2 0
4. Functional Description

Figure 4. Si4844-B Functional Block Diagram

4.1. Overview Like other successful audio products from Skyworks,
Si4844-B offers unmatched integration and PCB space
The Si4844-B is the analog-tuned digital-display digital
savings with minimum external components and small
CMOS AM/FM/SW radio receiver IC that integrates the
board area on a single side PCB. The high integration
complete receiver function from antenna input to audio
and complete system production test simplifies design-
output. Working with an external MCU with LCD/LED
in, increases system quality, and improves
driver, Si4844-B can output the AM/FM/SW
manufacturability. The receiver has very low power
frequencies, band, Bass/Treble and stereo/mono
consumption, runs off two AAA batteries, and delivers
information to display on LCD/LED, while using a simple
the performance benefits of high performance digital
potentiometer at the front end for analog-tune.
radio experience with digital display to the legacy
Leveraging Skyworks' proven and patented digital low
analog-tuned radio market.
intermediate frequency (low-IF) receiver architecture,
the Si4844-B delivers superior RF performance and The Si4844-B provides good flexibility in using the chip.
interference rejection in AM, FM and SW bands. The The frequency range of FM/AM/SW bands,
Si4844-B is pin-to-pin compatible with the current mono/stereo threshold, de-emphasis value, AM tuning
Si484x-A tuning. The Si4844-B shares the advanced step, AM soft mute level/rate, and Bass/Treble can be
features of the Si484x-A and can support a wider range either configured by the MCU or by using external
of FM and SW bands. It also supports China TV hardware to make a selection. The reference clock of
channels and audio reception in the FM band. The the FM tuner can be provided either by the crystal or by
superior control algorithm integrated in Si4844-B the host MCU within tolerance.
provides an easy and reliable control interface while Si4844-B also has flexibility in selecting bands and
eliminating all the manually tuned external components configuring band properties, enabling masked Host
used in traditional solutions. MCU for multiple projects, and reducing the cost of
development. Four tuning preferences are available to
meet different tuning preference requirements.

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 Si4844-B20
4.2. FM Receiver 4.3. AM Receiver
The Si4844-B integrates a low noise amplifier (LNA) The highly integrated Si4844-B supports worldwide AM
supporting the worldwide FM broadcast band (64 to band reception from 504 to 1750 kHz with five sub-
109 MHz) and the TV audio stations within the fre bands using a digital low-IF architecture with a minimum
quency range in China are also supported. The FM number of external components and no manual
band can also be configured to be a wider range such alignment required. This patented architecture allows
as 64–108 MHz in one band. for high-precision filtering, offering excellent selectivity
Pre-emphasis and de-emphasis is a technique used by and SNR with minimum variation across the AM band.
FM broadcasters to improve the signal-to-noise ratio of Similar to the FM receiver, the Si4844-B optimizes
FM receivers by reducing the effects of high frequency sensitivity and rejection of strong interferers, allowing
interference and noise. When the FM signal is better reception of weak stations.
transmitted, a pre-emphasis filter is applied to To offer maximum flexibility, the receiver supports a
accentuate the high audio frequencies. All FM receivers wide range of ferrite loop sticks from 180–450 μH. An
incorporate a de-emphasis filter which attenuates high air loop antenna is supported by using a transformer to
frequencies to restore a flat frequency response. Two increase the effective inductance from the air loop.
time constants are used in various regions. The de- Using a 1:5 turn ratio inductor, the inductance is
emphasis time constant can be chosen to be 50 or increased by 25 times and easily supports all typical AM
75 μs. Refer to “AN602: Si4822/26/27/40/44 Antenna, air loop antennas, which generally vary between 10 and
Schematic, Layout, and Design Guidelines.” 20 μH.
The Si4844-B also has advanced stereo blending that A 9, 10 kHz tuning step can be chosen by the external
employs adaptive noise suppression. As a signal resistor or host MCU according to the different regions,
quality degrades, the Si4844-B gradually combines the and AM soft mute level can be programmed by the host
stereo left and right audio channels to a mono audio MCU to have different tuning experiences. One of the
signal to maintain optimum sound fidelity under varying AM bands can be configured as a universal AM band
reception conditions. The Si4844-B can output a stereo that simultaneously supports 9 kHz and 10 kHz channel
signal to MCU with LCD/LED driver to display on the spaces for all regional AM standards worldwide. Refer
LCD/LED so that the user can easily discern the signal to “AN610: Si48xx ATDD Programming Guide” and
quality. “AN602: Si4822/26/27/40/44 Antenna, Schematic,
The stereo on signal is defined using both RSSI and the Layout, and Design Guidelines” for more details.
Left and Right separation levels as these two
specifications are the primary factors for stereo 4.4. SW Receiver
listening. The criteria can be set between two The Si4844-B supports short wave band receptions
conditions: the Left and Right channels are separated from 2.3 to 28.5 MHz in 5 kHz step size increments. It
by more than 6 dB with RSSI at >20 dB or Left and can also be configured to have a wide SW band that
Right channels are separated by more than 12 dB with can be used in SW radio with 1 or 2 SW banks. Si4844-
RSSI at >28 dB. The selection can be set up using B supports extensive short wave features such as
different values of the external resistor or configured by minimal discrete components and no factory
the host MCU. Refer to “AN602: Si4822/26/27/40/44 adjustments. The Si4844 supports using the FM
Antenna, Schematic, Layout, and Design Guidelines.” antenna to capture short wave signals. Refer to
The user can also refer to the “AN610: Si48xx ATDD “AN610: Si48xx ATDD Programming Guide” and
Programming Guide” for those who want to configure “AN602: Si4822/26/27/40/44 Antenna, Schematic,
the value by host MCU. Layout, and Design Guidelines” for more details.

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 Si4844-B20
4.5. Frequency Tuning 4.9. Stereo Audio Processing
A valid channel can be found by tuning the The output of the FM demodulator is a stereo
potentiometer that is connected to the TUNE1 and multiplexed (MPX) signal. The MPX standard was
TUNE2 pin of the Si4844-B chip. developed in 1961, and is used worldwide. Today's
MPX signal format consists of left + right (L+R) audio,
To offer easy tuning, the Si4844-B also outputs the
left – right (L–R) audio, a 19 kHz pilot tone.
tuned information to the MCU with LCD/LED driver to
display. It will light up the icon on display if the RF signal
quality passes a certain threshold when tuned to a valid

Modulation Level
station. Multiple tuning preferences are available. The
user can choose to have the best performance (volume, Mono Audio
Left + Right Stereo
stereo/mono effect) only at the exact channel, or the Pilot
Stereo Audio
Left - Right
RDS/
RBDS
best performance in a larger range. Refer to "AN610:
Si48xx ATDD Programming Guide" for more details.
4.6. Band Select 0 15 19 23 38 53 57
Frequency (kHz)
The Si4844-B supports worldwide AM band with five
sub-bands, US/Europe/Japan/China FM band with five Figure 5. MPX Signal Spectrum
sub-bands, and SW band with 16 sub-bands. Si4844-B 4.9.1. Stereo Decoder
provides the flexibility to configure the band and band The Si4844-B's integrated stereo decoder automatically
properties at either the MCU side or the Tuner side, decodes the MPX signal using DSP techniques. The 0
enabling masked MCU for multiple projects. For details to 15 kHz (L+R) signal is the mono output of the FM
on band selection, refer to “AN602: Si4822/26/27/40/44 tuner. Stereo is generated from the (L+R), (L–R), and a
Antenna, Schematic, Layout, and Design Guidelines” 19 kHz pilot tone. The pilot tone is used as a reference
and "AN610: Si48xx ATDD Programming Guide". to recover the (L–R) signal. Output left and right
4.7. Bass and Treble channels are obtained by adding and subtracting the
(L+R) and (L–R) signals respectively.
The Si4844-B further supports Bass/Treble tone control
for superior sound quality. The Si4844-B can be set to 4.9.2. Stereo-Mono Blending
be default normal, or programmed by the host MCU I2C- Adaptive noise suppression is employed to gradually
compatible 2-wire mode. FM has nine levels combine the stereo left and right audio channels to a
Bass/Treble effect and AM/SW has seven levels mono (L+R) audio signal as the signal quality degrades
Bass/Treble effect. For further configuration details, to maintain optimum sound fidelity under varying
refer to "AN610: Si48xx ATDD Programming Guide." reception conditions. Three metrics, received signal
strength indicator (RSSI), signal-to-noise ratio (SNR),
4.8. Volume Control and multipath interference, are monitored
The Si4844-B not only allows users to use the simultaneously in forcing a blend from stereo to mono.
traditional PVR wheel volume control through an The metric which reflects the minimum signal quality
external speaker amplifier, it also supports digital takes precedence and the signal is blended
volume control programmed by the host MCU. Si4844-B appropriately.
can be programmed to be Bass/Treble mode only or All three metrics have programmable stereo/mono
digital volume mode only; it can also be programmed to thresholds and attack/release rates. If a metric falls
have the digital volume coexist with Bass/Treble in two below its mono threshold, the signal is blended from
modes. Refer to "AN610: Si48xx ATDD Programming stereo to full mono. If all metrics are above their
Guide" and “AN602: Si4822/26/27/40/44 Antenna, respective stereo thresholds, then no action is taken to
Schematic, Layout, and Design Guidelines” for more blend the signal. If a metric falls between its mono and
details. stereo thresholds, then the signal is blended to the level
proportional to the metric’s value between its mono and
stereo thresholds, with an associated attack and
release rate.

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 Si4844-B20
4.10. Stereo DAC 4.14. Memorizing Status
High-fidelity stereo digital-to-analog converters (DACs) The Si4844-B provides the feature to memorize status
drive analog audio signals onto the LOUT and ROUT from the last power down with a simple design on PCB,
pins. The audio output may be muted. including frequency of the FM/AM/SW station. Refer to
“AN602: Si4822/26/27/40/44 Antenna, Schematic,
4.11. Soft Mute Layout, and Design Guidelines” for details.
The soft mute feature is available to attenuate the audio
outputs and minimize audible noise in very weak signal 4.15. Programming with Commands
conditions. An advanced algorithm is implemented to To ease development time and offer maximum
get a better analog tuning experience. The soft mute customization, the Si4844-B provides a simple yet
feature is triggered by the SNR metric. The SNR powerful software interface to program the receiver. The
threshold for activating soft mute is programmable, as device is programmed using commands, arguments,
are soft mute attenuation levels and attack and decay properties, and responses.
rates. To perform an action, the user writes a command byte
4.12. Reference Clock and associated arguments, causing the chip to execute
the given command. Commands control an action such
The Si4844-B supports programmable RCLK input (to as powerup the device, shut down the device, or get the
XTALI pin) with the spec listed in Table 7. It can be current tuned frequency. Arguments are specific to a
shared with the host MCU to save extra crystal. given command and are used to modify the command.
An onboard crystal oscillator is available to generate the Properties are a special command argument used to
32.768 kHz reference when an external crystal and modify the default chip operation and are generally
load capacitors are provided. Refer to "AN602: configured immediately after powerup. Examples of
Si4822/26/27/40/44 Antenna, Schematic, Layout, and properties are de-emphasis and soft mute attenuation
Design Guidelines" for more details. threshold.
4.13. Reset, Powerup, and Powerdown Responses provide the user information and are
echoed after a command and associated arguments are
Setting the RSTB pin low will disable analog and digital
issued. All commands provide a 1-byte status update,
circuitry, reset the registers to their default settings, and
indicating interrupt and clear-to-send status information.
disable the bus. Setting the RSTB pin high will bring the
device out of reset. For a detailed description of the commands and
properties for the Si4844-B, see "AN610: Si48xx ATDD
Figure 1 shows typical reset, startup, and shutdown
Programming Guide."
timings for the Si4844-B. RSTB must be held low
(asserted) during any power supply transitions and kept
asserted as specified in Figure 1 after the power
supplies are ramped up and stable. Failure to assert
RSTB as indicated here may cause the device to
malfunction and may result in permanent device
damage.
A powerdown mode is available to reduce power
consumption when the part is idle. Putting the device in
powerdown mode will disable analog and digital circuitry
while keeping the bus active.

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Si 4844- B2 0
5. Commands and Properties

Table 11. Si4844-B20 FM Receiver Command Summary

Cmd Name Description

0xE0 ATDD_GET_STATUS Get tune freq, band and etc status of the device.

0xE1 ATDD_POWER_UP Power up device, band selection and band properties setup.

0xE2 ATDD_AUDIO_MODE Audio output mode: get/set audio mode and settings.

0x10 GET_REV Returns the revision information of the device.

0x11 POWER_DOWN Power down device.

0x12 SET_PROPERTY Sets the value of a property.

0x13 GET_PROPERTY Retrieve a property's value.

Note: The Si4844-B has its own power up and get status commands which are different from previous Si47xx tuner parts. To
differentiate, we use “ATDD_POWER_UP” and “ATDD_GET_STATUS” to denote the ATDD-specific commands
instead of the general Si47xx “POWER_UP” and “STATUS” commands.

Table 12. Si4844-B20 FM Receiver Property Summary

Prop Name Description Default

0x0201 REFCLK_FREQ Sets frequency of reference clock in Hz. The range is 31130 to 0x8000
34406 Hz, or 0 to disable the AFC. Default is 32768 Hz.
0x0202 REFCLK_PRESCALE Sets the prescaler value for RCLK input. 0x0001

0x1100 FM_DEEMPHASIS Sets de-emphasis time constant. Default is 75 s. 0x0002

0x1300 FM_SOFT_MUTE_RATE Sets the attack and decay rates when entering and leaving soft 0x0040
mute.
0x1301 FM_SOFT_MUTE_SLOPE Configures attenuation slope during soft mute in dB attenuation per 0x0002
dB SNR below the soft mute SNR threshold. Default value is 2.
0x1302 FM_SOFT_MUTE_MAX_ Sets maximum attenuation during soft mute (dB). Set to 0 to disable 0x0010
ATTENUATION soft mute. Default is 16 dB.

0x1303 FM_SOFT_MUTE_ Sets SNR threshold to engage soft mute. Default is 4 dB. 0x0004
SNR_THRESHOLD

0x1207 FM_STEREO_IND_ Sets the blend threshold for stereo indicator. Default value is band- 0x9F
BLEND_THRESHOLD dependent (either 0x9F or 0xB2). 0xB2

0x1800 FM_BLEND_RSSI_ Sets RSSI threshold for stereo blend. (Full stereo above threshold, 0x0031
STEREO_THRESHOLD blend below threshold.) To force stereo, set this to 0. To force mono,
set this to 127. Default value is 49 dBV.
0x1801 FM_BLEND_RSSI_ Sets RSSI threshold for mono blend (Full mono below threshold, 0x0008
MONO_THRESHOLD blend above threshold). To force stereo, set this to 0. To force 0x0007
mono, set this to 127. Default value is band-dependent (either 8 or
7).
0x4000 RX_VOLUME Sets the output volume. 0x003F

0x4001 RX_HARD_MUTE Mutes the audio output. L and R audio outputs may be muted inde- 0x0000
pendently.
0x4002 RX_BASS_TREBLE Sets the output bass/treble level. 0x0004

0x4003 RX_ACTUAL_VOLUME Reads the actual output volume. 0x003F

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 Si4844-B20

Table 13. Si4844-B20 AM/SW Receiver Command Summary

Cmd Name Description

0xE0 ATDD_GET_STATUS Get tune freq, band and etc status of the device.

0xE1 ATDD_POWER_UP Power up device, band selection and band properties setup

0xE2 ATDD_AUDIO_MODE Audio output mode: get/set audio mode settings.

0x10 GET_REV Returns the revision information of the device.

0x11 POWER_DOWN Power down device.

0x12 SET_PROPERTY Sets the value of a property.

0x13 GET_PROPERTY Retrieve a property's value.

Note: The Si4844-B has its own power up and get status commands which are different from previous Si47xx tuner parts. To
differentiate, we use “ATDD_POWER_UP” and “ATDD_GET_STATUS” to denote the ATDD-specific commands
instead of the general Si47xx “POWER_UP” and “STATUS” commands.

Table 14. Si4844-B20 AM/SW Receiver Property Summary

Prop Name Description Default

0x0201 REFCLK_FREQ Sets frequency of reference clock in Hz. The range is 31330 to 0x8000
34406 Hz, or 0 to disable the AFC. Default is 32768 Hz.
0x0202 REFCLK_PRESCALE Sets the prescaler value for RCLK input. 0x0001

0x4000 RX_VOLUME Sets the output volume. 0x003F

0x4001 RX_HARD_MUTE Mutes the audio output. L and R audio outputs may be muted 0x0000
independently.
0x4002 RX_BASS_TREBLE Sets the output bass/treble level. 0x0003

0x4003 RX_ACTUAL_VOLUME Read the actual output volume 0x003F

0x3300 AM_SOFT_MUTE_RATE Sets the attack and decay rates when entering and leaving soft 0x0040
mute.
0x3301 AM_SOFT_MUTE_SLOPE Configures attenuation slope during soft mute in dB attenuation 0x0002
per dB SNR below the soft mute SNR threshold.
0x3302 AM_SOFT_MUTE_ Sets maximum attenuation during soft mute (dB). Set to 0 to dis- 0x0010
MAX_ATTENUATION able soft mute.

0x3303 AM_SOFT_MUTE_ Sets SNR threshold to engage soft mute. 0x0008

SNR_THRESHOLD

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Si 4844- B2 0
6. Pin Description: Si4844-B

LNA_EN 1 24 LOUT
IRQ 2 23 ROUT
TUNE1 3 22 DBYP
TUNE2 4 21 VDD2
BAND 5 20 VDD1
NC 6 19 XTALI
NC 7 18 XTALO
FMI 8 17 SCLK
RFGND 9 16 SDIO
NC 10 15 RST
NC 11 14 GND
AMI 12 13 GND

Pin Number(s) Name Description

1 LNA_EN Enabling SW external LNA
2 IRQ Interrupt Request
3 TUNE1 Frequency tuning
4 TUNE2 Frequency tuning
5 BAND Band selection and De-emphasis/Stereo separation selection
6,7 NC No connect. Leave floating.
8 FMI FM RF inputs. FMI should be connected to the antenna trace.
9 RFGND RF ground. Connect to ground plane on PCB.
10, 11 NC Unused. Tie these pins to GND.
12 AMI AM RF input. AMI should be connected to the AM antenna.
13, 14 GND Ground. Connect to ground plane on PCB.
15 /RST Device reset (active low) input
16 SDIO Serial data input/output
17 SCLK Serial clock input
18 XTALO Crystal oscillator output
19 XTALI Crystal oscillator input /external reference clock input.
20 VDD1 Supply voltage. May be connected directly to battery.
21 VDD2 Supply voltage. May be connected directly to battery.
22 DBYP Dedicated bypass for VDD
23 ROUT Right audio output
24 LOUT Left audio output

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 Si4844-B20
7. Ordering Guide

Part Number* Description Package Type Operating

Temperature/Voltage

Si4844-B20-GU AM/FM/SW Broadcast Radio Receiver 24L SSOP Pb-free –15 to 85 °C

2.0 to 3.6 V

*Note: Add an “(R)” at the end of the device part number to denote tape and reel option. The devices will typically operate at
25 °C with degraded specifications for VDD voltage ramped down to 2.0 V.

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Si 4844- B2 0
8. Package Outline: Si4844-B20
The 24-pin SSOP illustrates the package details for the Si4844-B20. Table 15 lists the values for the dimensions
shown in the illustration.

Figure 6. 24-Pin SSOP

Table 15. Package Dimensions

Dimension Min Nom Max
A — — 1.75
A1 0.10 — 0.25
b 0.20 — 0.30
c 0.10 — 0.25
D 8.65 BSC
E 6.00 BSC
E1 3.90 BSC
e 0.635 BSC
L 0.40 — 1.27
θ 0° — 8°
aaa 0.20
bbb 0.18
ccc 0.10
ddd 0.10
Notes:
1. All dimensions shown are in millimeters (mm) unless otherwise noted.
2. Dimensioning and Tolerancing per ANSI Y14.5M-1994.
3. This drawing conforms to the JEDEC Solid State Outline MO-137, Variation AE.
4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification
for Small Body Components.

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 Si4844-B20
9. PCB Land Pattern: Si4844-B20
Figure 7 illustrates the PCB land pattern details for the Si4844-B20-GU SSOP. Table 16 lists the values for the
dimensions shown in the illustration.

Figure 7. PCB Land Pattern

Table 16. PCB Land Pattern Dimensions

Dimension Min Max
C 5.20 5.40
E 0.635 BSC
X1 0.35 0.45
Y1 1.55 1.75
General:
1. All dimensions shown are in millimeters (mm) unless otherwise noted.
2. This land pattern design is based on the IPC-7351 guidelines.
Solder Mask Design:
3. All metal pads are to be non-solder mask defined (NSMD). Clearance between the
solder mask and the metal pad is to be 60 µm minimum, all the way around the pad.
Stencil Design:
4. A stainless steel, laser-cut, and electro-polished stencil with trapezoidal walls
should be used to assure good solder paste release.
5. The stencil thickness should be 0.125 mm (5 mils).
6. The ratio of stencil aperture to land pad size should be 1:1 for all perimeter pads.
Card Assembly:
7. A No-Clean, Type-3 solder paste is recommended.
8. The recommended card reflow profile is per the JEDEC/IPC J-STD-020
specification for Small Body Components.

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Si 4844- B2 0
10. Top Marking: Si4844-B20

4844B20GU
YYWWTTTTTT
Mark Method: YAG Laser
Line 1 Marking: Device identifier 4844B20GU = Si4844-B20
YY = Year
Line 2 Marking: WW = Work week Assigned by the Assembly House.
TTTTTT = Manufacturing code

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 Si4844-B20
11. Additional Reference Resources
Contact your local sales representatives for more information or to obtain copies of the following references:
 EN55020 Compliance Test Certificate
 AN602: Si4822/26/27/40/44 Antenna, Schematic, Layout, and Design Guidelines
 AN603: Si4822/26/27/40/44 DEMO Board Test Procedure
 Si4844-DEMO Board User’s Guide
 AN610: Si48xx-ATDD Programming Guide

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Si 4844- B2 0
DOCUMENT CHANGE LIST
Revision 0.1 to Revision 1.0
 Updated “Features”
 Updated Table 3. "Reset Timing Characteristics"
 Updated Table 5. “FM Receiver Characteristics”
 Updated Table 6. “AM/SW Receiver Characteristics”
 Updated Section 4.3. “AM Receiver”
 Inserted Section 4.13. "Reset, Powerup, and
Powerdown"
 Updated Section 6. “Pin Description: Si4844-B”

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 Connecting Everyone

and Everything,

All the Time

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Copyright © 2021 Skyworks Solutions, Inc. All Rights Reserved.

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