®

RT6150A/B

Current Mode Buck-Boost Converter

General Description Features
The RT6150A/B is a high efficiency, fixed frequency, Buck-  Single Inductor
Boost DC/DC converter that operates from input voltages  Fixed Frequency Operation with Battery Voltages
above, below or equal to the output voltage. The topology  Synchronous Rectification : Up to 90% Efficiency
incorporated in the IC provides a continuous transfer  Up to 800mA Continuous Output Current
function through all operating modes, making the product  VOUT Disconnected from VIN during Shutdown
ideal for single lithium-ion, multi-cell alkaline or Ni-MH  1.8V to 5.5V Input and Output Range
battery applications where the output voltage is within the  Power Save Mode (PSM) Enable Control
battery voltage range.  <1μμA Shutdown Current
 10-Lead WDFN Packages
The device includes two N-MOSFET switches and two P-
 RoHS Compliant and Halogen Free
MOSFET switches for high efficiency operation. Switching
frequency is set at 1MHz to reduce the external
component size. Quiescent current is only 60μA in Power Ordering Information
Save Mode (PSM), maximizing battery life in portable RT6150A/B
applications. PSM operation is user controlled and can Package Type
be enabled by driving the PS pin low. If the PS pin is QW : WDFN-10L 3x3 (W-Type)
QW : WDFN-10L 2.5x2.5 (W-Type)
driven high, then fixed frequency switching is enabled.
Lead Plating System
Other features include low shutdown current, internal,
G : Green (Halogen Free and Pb Free)
soft-start control, thermal shutdown protection and current
A : WDFN-10L 3x3
limit. The RT6150A is available in the WDFN-10L 3x3
B : WDFN-10L 2.5x2.5
package and the RT6150B is available in the WDFN-10L
Note :
2.5x2.5 package.
Richtek products are :
 RoHS compliant and compatible with the current require-
Applications ments of IPC/JEDEC J-STD-020.
 Portable Products  Suitable for use in SnPb or Pb-free soldering processes.
 Handheld Instrumentation

Simplified Application Circuit

LX1 LX2
RT6150A/B
Battery VIN VOUT VOUT
R1
VINA
FB
Enable EN R2

PS
GND

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RT6150A/B
Marking Information Pin Configurations
RT6150AGQW
(TOP VIEW)
0N= : Product Code
YMDNN : Date Code VOUT 1 10 FB
0N=YM LX2 9
2 GND

GND
DNN GND 3 8 VINA
LX1 4 7 PS
VIN 5 11 6 EN

WDFN-10L 3x3 / WDFN-10L 2.5x2.5

RT6150BGQW
00 : Product Code

00W W : Date Code

Functional Pin Description

Pin No. Pin Name Pin Function
Output of the Buck-Boost Converter. Connect a capacitor between the
1 VOUT
VOUT and GND.
2 LX2 Second Switch Node. Connect this pin to the inductor.
3, 9, Power Ground. The exposed pad must be soldered to a large PCB and
GND
11 (Exposed Pad) connected to GND for maximum power dissipation.
4 LX1 First Switch Node. Connect this pin to the inductor.
Power Input. Connect an at least 10F capacitor between the VIN pin and
5 VIN
GND.
6 EN Enable Control Input for the Buck-Boost Converter.
PSM Control Input. Pull low for PSM operation and pull high for fixed
7 PS
switching frequency operation.
8 VINA Supply Voltage Input for Control Circuit.
Feedback Input. Connect a resistive divider to set the output voltage. The
10 FB
output voltage can be adjusted from 1.8V to 5.5V.

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 RT6150A/B
Function Block Diagram
LX1 LX2

VIN VOUT

Gate Driver

VINA
OCP Zero Current
ISENSE

Temp OTP VPSM

CTRL
Control
PS
EN
OSC

CMP
SS
+
VREF
+ AMP
-
FB
+
CC
Slop Comp

RC

GND

Operation
The RT6150A/B is a synchronous average current mode switching Buck-Boost converter designed to maintain a fixed
output voltage from an input supply that can be above, equal, or below the output voltage. The average inductor current
is regulated by a fast current regulator which is controlled by a voltage control loop. The voltage error amplifier gets its
feedback input from the FB pin. For adjustable output voltage, a resistive voltage divider must be connected to the FB
pin. When VIN is greater than VOUT, the device operates in Buck mode. When VIN is lower than VOUT, the device
operates in Boost mode. When VIN is close to VOUT, the RT6150A/B automatically enters Buck-Boost mode. In Buck-
Boost mode, the converter will maintain the regulation for output voltage and keep a minimum current ripple in the
inductor to guarantee good performance.

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RT6150A/B
Absolute Maximum Ratings (Note 1)
 VOUT, VIN, EN, PS, VINA, FB Pin ------------------------------------------------------------------------------------ −0.3V to 6V
 Switch Output Voltage, LX1, LX2 Pin ---------------------------------------------------------------------------------- −0.3V to 6V
< 10ns ------------------------------------------------------------------------------------------------------------------------- −2V to 7.5V
 Power Dissipation, PD @ TA = 25°C
WDFN-10 3x3 --------------------------------------------------------------------------------------------------------------- 3.28W
WDFN-10 2.5x2.5 ---------------------------------------------------------------------------------------------------------- 2.44W
 Package Thermal Resistance (Note 2)
WDFN-10 3x3, θJA ---------------------------------------------------------------------------------------------------------- 30.5°C/W
WDFN-10 3x3, θJC --------------------------------------------------------------------------------------------------------- 7.5°C/W
WDFN-10 2.5x2.5, θJA ----------------------------------------------------------------------------------------------------- 40.9°C/W
WDFN-10 2.5x2.5, θJC ---------------------------------------------------------------------------------------------------- 18.6°C/W
 Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------------- 260°C
 Junction Temperature ------------------------------------------------------------------------------------------------------ 150°C
 Storage Temperature Range --------------------------------------------------------------------------------------------- −65°C to 150°C
 ESD Susceptibility (Note 3)
HBM (Human Body Model) ----------------------------------------------------------------------------------------------- 2kV
MM (Machine Model) ------------------------------------------------------------------------------------------------------ 200V

Recommended Operating Conditions (Note 4)

 Supply Input Voltage, VIN ------------------------------------------------------------------------------------------------ 1.8V to 5.5V
 Junction Temperature Range --------------------------------------------------------------------------------------------- −40°C to 125°C
 Ambient Temperature Range --------------------------------------------------------------------------------------------- −40°C to 85°C

Electrical Characteristics
(VIN = VOUT = 3.6V, TA = 25° C, unless otherwise specified.)
Parameter Symbol Test Conditions Min Typ Max Unit
Input Voltage High-Level -- 1.65 1.8
V
UVLO Low-Level 1.4 1.55 --
Feedback Voltage V FB VPS = VIN 0.495 0.5 0.505 V
Feedback Input Current VFB = 0.5V -- 1 50 nA
IOUT = 0mA, PS = 0V (Note 5)
-- 60 --
Power Save Mode
Quiescent Current A
EN = 0V, Not Including Switch
-- 0.1 1
Leakage Shutdown
N-MOSFET Switch Leakage -- 0.1 5 A
P-MOSFET Switch Leakage -- 0.1 10 A
N-MOSFET Switch On
RDS(ON)_N -- 0.15 -- 
Resistance
P-MOSFET Switch On
RDS(ON)_P -- 0.15 -- 
Resistance
Switch Current Limit I LIM VIN = 3.6V 1.6 -- -- A
Oscillator Frequency f OSC 0.8 1 1.2 MHz

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 RT6150A/B
Parameter Symbol Test Conditions Min Typ Max Unit
EN and PS Input Logic-High 1.2 -- --
V
Voltage Logic-Low -- -- 0.4

EN and PS Input Current VEN = VPS = VIN -- 0.01 1 A

Thermal Shutdown T SD -- 140 -- C

Note 1. Stresses beyond those listed “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 may
affect device reliability.
Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is
measured at the exposed pad of the package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Note 5. Current measurements are performed when the output are not switching.

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RT6150A/B
Typical Application Circuit

RT6150A/B
5
VIN VIN VOUT 1 VOUT
CIN R1 COUT
10µF 8 487k 20µF
VINA
10
FB
6 R2
Enable EN 2 86.6k
LX2
7 L
PS 2.2µH
LX1 4
GND
3, 9, 11 (Exposed Pad)

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 RT6150A/B
Typical Operating Characteristics
Buck-Boost 3.3V Efficiency Buck-Boost 3.3V Efficiency
100 100
90 90
80 80
70 VIN = 1.8V 70 VIN = 1.8V

Efficiency (%)
Efficiency (%)

VIN = 2.4V VIN = 2.4V

60 VIN = 3.3V 60 VIN = 3.3V
50 VIN = 4.2V 50 VIN = 4.2V
VIN = 5.5V VIN = 5.5V
40 40
30 30
20 20
10 10
L = 2.2μH, COUT = 20μF, PS/SYNC = L L = 2.2μH, COUT = 20μF, PS/SYNC = H
0 0
1 10 100 1000 1 10 100 1000
Output Current (mA) Output Current (mA)

Efficiency vs. Input Voltage Output Voltage vs. Output Current

100 3.6
90
3.5
80
Output Voltage (V)

70 IOUT = 500mA
Efficiency (%)

IOUT = 100mA 3.4

60 IOUT = 10mA
50 3.3 VIN = 1.8V
40 VIN = 2.4V
3.2 VIN = 3.3V
30 VIN = 4.2V
20 VIN = 5V
3.1
10
L = 2.2μH, COUT = 20μF, PS/SYNC = L COUT = 20μF, PS = L
0 3.0
1.8 2.54 3.28 4.02 4.76 5.5 0 200 400 600 800 1000
Input Voltage (V) Output Current (mA)

Output Voltage vs. Input Voltage Maximum Output Current vs. Input Voltage
3.6 2000
Maximum Output Current (mA)1

1750
3.5
1500
Output Voltage (V)

3.4
1250

3.3 IOUT = 500mA 1000

IOUT = 300mA
IOUT = 100mA 750
3.2
500
3.1
250
COUT = 20μF, PS = L VOUT = 3.3V, COUT = 20μF, PS = H
3.0 0
1.8 2.54 3.28 4.02 4.76 5.5 1.8 2.54 3.28 4.02 4.76 5.5
Input Voltage (V) Input Voltage (V)

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RT6150A/B

Output Voltage Ripple Output Voltage Ripple

LX1 LX1
(2V/Div) (2V/Div)

LX2 LX2
(2V/Div) (2V/Div)
VOUT_ac VOUT_ac
(20mV/Div) (20mV/Div)
VIN = 2.5V, VOUT = 3.3V, VIN = 3.3V, VOUT = 3.3V,
IOUT = 500mA, L = 2.2μH, COUT = 20μF IOUT = 500mA, L = 2.2μH, COUT = 20μF

Time (500ns/Div) Time (500ns/Div)

Output Voltage Ripple Load Transient Response

LX1
(2V/Div)
I LOAD
(200mA/Div)
LX2
VOUT_ac
(2V/Div)
(100mV/Div)
VOUT_ac
(20mV/Div)
VIN = 4.2V, VOUT = 3.3V, VIN = 3V, VOUT = 3.3V,
IOUT = 500mA, L = 2.2μH, COUT = 20μF IOUT = 200mA to 600mA, L = 2.2μH, COUT = 20μF

Time (500ns/Div) Time (2.5ms/Div)

Load Transient Response Load Transient Response

I LOAD I LOAD
(200mA/Div) (200mA/Div)
VOUT_ac VOUT_ac
(100mV/Div) (100mV/Div)

VIN = 3.3V, VOUT = 3.3V, VIN = 4.2V, VOUT = 3.3V,

IOUT = 200mA to 600mA, L = 2.2μH, COUT = 20μF IOUT = 200mA to 600mA, L = 2.2μH, COUT = 20μF

Time (2.5ms/Div) Time (2.5ms/Div)

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 RT6150A/B
Application Information
The RT6150A/B Buck-Boost DC/DC converter is designed Power Save Mode
for systems powered by one-cell Li-Ion or Li-Polymer The PS pin can be used to select different operation
battery with a typical voltage between 2.5V and 4.2V. They modes. To enable Power Save Mode (PSM), the PS pin
can also be used in systems powered by a double or must be set at low. The PSM is used to improve the
triple cell Alkaline, NiCd, or NiMH battery with a typical efficiency at light load. If the power save mode is disabled
terminal voltage between 1.8V and 5.5V. Additionally, the by pulling high the PS pin, the converter will operate in
output voltage can be set between 1.8V and 5.5V. PWM mode with fixed switching frequency.
The controller monitors the average input current as well
Under-Voltage Lockout
as the peak input current. With this, maximum input power
can be controlled to achieve a safe and stable operation. The under-voltage lockout circuit prevents the device from
To protect the device from overheating, an internal operating incorrectly at low input voltages. It prevents the
temperature sensor is implemented. converter from turning on the power switches under
undefined conditions and prevents the battery from deep
Enable discharge. VINA voltage must be greater than 1.65V to
The device can be enabled or disenabled by the EN pin. enable the converter. During operation, if VINA voltage
When the EN pin is higher than the threshold of logic- drops below 1.55V, the converter is disabled until the
high, the device starts operation with soft-start. Once the supply exceeds the UVLO rising threshold. The
EN pin is set at low, the device will be shut down. In RT6150A/B automatically restarts if the input voltage
shutdown mode, the converter stops switching, internal recovers to the input voltage UVLO high level.
control circuitry is turned off, and the load is disconnected
Thermal Shutdown
from the input. This also means that the output voltage
can drop below the input voltage during shutdown. The device has a built-in temperature sensor which
monitors the internal junction temperature. If the
Soft-Start temperature exceeds the threshold, the device stops
When the RT6150A/B is enabled, the output voltage will operating. As soon as the IC temperature has decreased
increase from 0V to its setting value within 4ms. During below the threshold with a hysteresis, it starts operating
start-up period, the duty cycle and the peak current are again. The built-in hysteresis is designed to avoid unstable
limited to reduce high peak current flowing from the input. operation at IC temperatures near the over temperature
threshold.
Output Voltage Setting
The output voltage is adjustable by an external resistive Inductor Selection
divider. The resistive divider must be connected between To properly configure the Buck-Boost converter, an
VOUT, FB and GND. When the output voltage is regulated inductor must be connected between the LX1 and LX2
properly, the typical value of the voltage at the FB pin is pins. To estimate the inductance value, two equations are
500mV. The maximum recommended value for the output listed as below :
voltage is 5.5V. The VOUT can be calculated by the VOUT   VIN(MAX)  VOUT 
L1 > (H)
equation as below : f  IL  VIN(MAX)

VOUT = (1+R1/R2) x VFB VIN(MIN)   VOUT  VIN(MIN) 

L2 > (H)
f  IL  VOUT
It is recommended to use a 487kΩ resistor for R1. For
where f is the minimum switching frequency. L1 is the
better transient response performance, adding a feed-
minimum inductor value for Buck mode operation. VIN(MAX)
forward capacitor in parallel with R1 is recommended.
is the maximum input voltage. L2 is the minimum

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RT6150A/B
inductance, for Boost mode operation. VIN(MIN) is the A capacitor with a value in the range of the calculated
minimum input voltage. The recommended minimum minimum should be used. This is required to maintain
inductor value is either L1 or L2 whichever is higher. For control loop stability. There are no additional requirements
example, a suitable inductor value is 2.2μH for generating regarding minimum ESR. Low ESR capacitors should be
a 3.3V output voltage from a Li-Ion battery with the range used to minimize output voltage ripple. Larger capacitors
from 2.5V to 4.2V. The recommended inductor value range will cause lower output voltage ripple as well as lower
is between 1.5μH and 4.7μH. In general, a higher inductor output voltage drop during load transients.
value offers better performance in high voltage conversion
condition. Thermal Considerations
For continuous operation, do not exceed absolute
Input Capacitor Selection maximum junction temperature. The maximum power
At least a 10μF input capacitor is recommended to improve dissipation depends on the thermal resistance of the IC
transient behavior of the regulator and EMI behavior of the package, PCB layout, rate of surrounding airflow, and
total power supply circuit. A ceramic capacitor placed as difference between junction and ambient temperature. The
close as possible to the VIN and GND pins of the IC is maximum power dissipation can be calculated by the
recommended. following formula :
PD(MAX) = (TJ(MAX) − TA) / θJA
Output Capacitor Selection
The output capacitor selection determines the output where TJ(MAX) is the maximum junction temperature, TA is
voltage ripple and transient response. It is recommended the ambient temperature, and θJA is the junction to ambient
to use ceramic capacitors placed as close as possible to thermal resistance.
the VOUT and GND pins of the IC. If, for any reason, the For recommended operating condition specifications, the
application requires the use of large capacitors which can maximum junction temperature is 125°C. The junction to
not be placed close to the IC, using a small ceramic ambient thermal resistance, θJA, is layout dependent. For
capacitor in parallel to the large one is recommended. WDFN-10L 3x3 package, the thermal resistance, θJA, is
This small capacitor should be placed as close as possible 30.5°C/W on a standard JEDEC 51-7 four-layer thermal
to the VOUT and GND pins of the IC. The output voltage test board. For WDFN-10L 2.5x2.5 package, the thermal
ripple for a given output capacitor is expressed as follows : resistance, θJA, is 40.9°C/W on a standard JEDEC 51-7
VOUT  (VIN  VOUT ) four-layer thermal test board. The maximum power
VOUT , peak (Buck) =
VIN  8  L  (fOSC )2  COUT dissipation at TA = 25°C can be calculated by the following
I  (VOUT  VIN ) formula :
VOUT , peak (Boost) = LOAD
COUT  VOUT  fOSC
PD(MAX) = (125°C − 25°C) / (30.5°C/W) = 3.28W for
If the RT6150A/B operates in Buck mode, the worst-case WDFN-10L 3x3 package
voltage ripple occurs at the highest input voltage. When
PD(MAX) = (125°C − 25°C) / (40.9°C/W) = 2.44W for
the RT6150A/B operates in boost mode, the worst-case
WDFN-10L 2.5x2.5 package
voltage ripple occurs at the lowest input voltage.
The maximum power dissipation depends on the operating
The maximum voltage of overshoot or undershoot, is
ambient temperature for fixed T J(MAX) and thermal
inversely proportional to the value of the output capacitor.
resistance, θJA. The derating curve in Figure 1 allows the
To ensure stability and excellent transient response, it is
designer to see the effect of rising ambient temperature
recommended to use a minimum of 10μF/X7R/1206
on the maximum power dissipation.
capacitors at the output. For surface mount applications,
Taiyo Yuden or TDK ceramic capacitors, X7R series Multi-
layer Ceramic Capacitor is recommended.

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 RT6150A/B
3.5 Layout Considerations
Maximum Power Dissipation (W)1

Four-Layer PCB
WDFN-10L 3x3
For the best performance of the RT6150A/B, the following
3.0
PCB layout guidelines must be strictly followed.
2.5
 Place the input and output capacitors as close as
2.0 possible to the input and output pins respectively for
WDFN-10L 2.5x2.5 good filtering.
1.5
 Keep the main power traces as wide and short as
1.0
possible.
0.5
 The switching node area connected to LX and inductor
0.0 should be minimized for lower EMI.
0 25 50 75 100 125
 Place the feedback components as close as possible
Ambient Temperature (°C)
to the FB pin and keep these components away from
Figure 1. Derating Curve of Maximum Power Dissipation
the noisy devices.
 Connect the GND and Exposed Pad to a strong ground
plane for maximum thermal dissipation and noise
protection.
 Directly connect the output capacitors to the feedback
network to avoid bouncing caused by parasitic
resistance and inductance from the PCB trace.

GND VOUT
R1
COUT The feedback divider
VOUT 1 10 FB R2 should be placed as
close as possible to
Input/Output LX2 2 9 GND
GND

the FB pin.
capacitors must be L GND 3 8 VINA VIN
placed as close as
LX1 4 7 PS
possible to the
Input/Output pin. VIN 5 11 6 EN
CIN

GND

LX should be connected to inductor by wide and short

trace. Keep sensitive components away from this trace.

Figure 2. PCB Layout Guide

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RT6150A/B
Outline Dimension

D2
D

E E2

SEE DETAIL A
1

e
b 2 1 2 1
A
A3
A1 DETAIL A
Pin #1 ID and Tie Bar Mark Options

Note : The configuration of the Pin #1 identifier is optional,

but must be located within the zone indicated.

Dimensions In Millimeters Dimensions In Inches

Symbol
Min Max Min Max
A 0.700 0.800 0.028 0.031
A1 0.000 0.050 0.000 0.002
A3 0.175 0.250 0.007 0.010
b 0.180 0.300 0.007 0.012
D 2.950 3.050 0.116 0.120
D2 2.300 2.650 0.091 0.104
E 2.950 3.050 0.116 0.120
E2 1.500 1.750 0.059 0.069
e 0.500 0.020
L 0.350 0.450 0.014 0.018

W-Type 10L DFN 3x3 Package

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 RT6150A/B

2 1 2 1

DETAIL A
Pin #1 ID and Tie Bar Mark Options

Note : The configuration of the Pin #1 identifier is optional,

but must be located within the zone indicated.

Dimensions In Millimeters Dimensions In Inches

Symbol
Min. Max. Min. Max.
A 0.700 0.800 0.028 0.031
A1 0.000 0.050 0.000 0.002
A3 0.175 0.250 0.007 0.010
b 0.200 0.300 0.008 0.012
D 2.400 2.600 0.094 0.102
D2 1.950 2.050 0.077 0.081
E 2.400 2.600 0.094 0.102
E2 1.150 1.250 0.045 0.049
e 0.500 0.020
L 0.350 0.450 0.014 0.018

W-Type 10L DFN 2.5x2.5 Package

Richtek Technology Corporation

14F, No. 8, Tai Yuen 1st Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789

Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should
obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot
assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be
accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third
parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries.

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