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RT9907
3 Channel DC/DC Converters IC with High-Efficiency Step-Up
and Step-Down
General Description
Features
The RT9907 is a three channel power-supply solution for
digital still cameras and other battery-powered devices. It
integrates an asynchronous step-up and two synchronous
step-down DC-DC converters. The RT9907 is targeted for
applications that use two AA cells or a single lithium-ion
battery.

1.5V to 5.5V Battery Input Voltage Range

Main step-up DC-DC Converter
 1.5V to 5.5V Adjustable Output Voltage
 Up to 90% Efficiency
 2.6A, 0.3Ω
Ω Internal Power Switch
Two Step-Down DC-DC Converters
 0.8V to 5.5V Adjustable Output Voltage
 94% Efficiency
 100% Duty Cycle
Up to 1.4MHz Switching Frequency
1uA Supply Current in Shutdown Mode
Programmable Soft Start Function
Independent Enable Pin (CH1, CH2, CH3)
External Compensation Network (CH1, CH2, CH3)
Short Circuit Protection (CH1, CH2, CH3)
Over Voltage Protection (CH2)
24-Lead VQFN Package
RoHS Compliant and 100% Lead (Pb)-Free
The three DC-DC converters (CH1, CH2, CH3) accept input
voltage from 1.5V to 5.5V. Each DC-DC converter has
better transient response and excellent stability by
providing current-mode control and external compensation
network. With built-in Internal MOSFET and up to 1.4MHz
operating frequency, the RT9907 allows minimum BOM
cost and PCB area.
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The step-down DC-DC converters (CH2, CH3) can regulate
output voltage as low as 0.8V. Three operational modes
are available: PWM, PSM, Low-Dropout modes. At PWM
mode, Internal synchronous rectifier with low RDS(ON)
dramatically reduces conduction loss and achieve 94%
efficiency. It enters Low-Dropout mode when normal PWM
cannot provide regulated output voltage by continuously
turning on the upper P-MOSFET. No external Schottky
diode is required in practical application.
Each DC-DC converter has independent enable input and
soft-start function allowing versatile power sequence
combination. Complete protection functions are
implemented such as short circuit, over-voltage protection.

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Applications



Digital Still Camera
PDAs
Portable Device
Pin Configurations
(TOP VIEW)
ments of IPC/JEDEC J-STD-020.

EN2
FB2
COMP2
EN3
19
18
EN1
VDD3
2
17
ENM
LX3
3
16
VDD2
PGND3
4
15
LX2
SS
5
14
PGND2
RT
6
13
LX1
GND
25
7
8
9
10
11
12
VDD1
RoHS compliant and compatible with the current require-
20
PGND1

21
COMP1
Richtek products are :
22
FB1
Note :
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
23
1
GND
Package Type
QV : VQFN-24L 4x4 (V-Type)
(Exposed Pad-Option 1)
24
COMP3
VDDM
RT9907
GND
Ordering Information
FB3
The RT9907 is available in small VQFN-24L 4x4 package.
VQFN-24L 4x4
Suitable for use in SnPb or Pb-free soldering processes.
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS9907-11 May 2014
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
RT9907
Typical Application Circuit
1-cell Li+ Battery 3.4V to 4.2V
V BAT
4.7H
10F
10F
0.1F
1F
10F x 2
4.7H
1.5V/500mA
200k
100pF
10F x 4
2
VDD3
3
LX3
24
VDDM
8
V BAT
LX1 13
SS0520
FB3
VDD1
12
5V/500mA
220k
680k
Chip Enable
17
ENM
18
EN1
21
22
130k
RT9907
VDD2
10k
19 COMP2
30k
1 COMP3
LX2
6
4
4.7H
3.3V/500mA
14 11
470k
20
10F x 4
150k
GND
PGND1
PGND2
PGND3
5 SS
15
100pF
FB2
1nF
V BAT
10F x 2
10 COMP1
1nF
16
EN3
20k
1nF
10F x 4
FB1
EN2
RT
4.7nF
9
7, 23,
Exposed Pad (25)
Figure 1. Typical Application Circuit for 1-cell Li+ Battery
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is a registered trademark of Richtek Technology Corporation.
DS9907-11 May 2014
RT9907
2-AA Battery 1.8V to 3.2V
1F
10F x 2
4.7H
1.5V/300mA
200k
100pF
10F x 4
3
24
VDDM
8
2
V BAT
VDD3
LX1 13
LX3
4.7H
SS0520
FB3
VDD1
12
I/O 3.3V/500mA
220k
470k
Chip Enable
9
17
ENM
18
EN1
21
22
150k
RT9907
VDD2
10k
19 COMP2
30k
1 COMP3
LX2
6
4.7H
2.5V/300mA
4 14 11
470k
20
10F x 4
220k
GND
PGND1
PGND2
PGND3
5 SS
15
100pF
FB2
1nF
3.3V
10F x 2
10 COMP1
1nF
16
EN3
20k
1nF
10F x 4
FB1
EN2
RT
4.7nF
V BAT
10F x 2
7, 23,
Exposed Pad (25)
Figure 2. Typical Application Circuit for 2-AA Battery Supply
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
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RT9907
Function Block Diagram
VDDM
ENM
EN
CH1
Current-MODE
Asynchronous
Step-Up
PWM
EN1
VDD1
LX1
PGND1
Boost
SS
Soft-Start
OSC
RT
PWM
OSC
COMP1
FB1
EN2
VDD2
CH2
Current-MODE
Synchronous
Step-Down
PWM
LX2
PGND2
Buck2
Thermal
Shutdown
COMP2
FB2
EN3
VDD3
CH3
Current-MODE
Synchronous
Step-Down
PWM
LX3
PGND3
Buck3
COMP3
FB3
GND
ENM
EN1
EN2
EN3
CH1
CH2
CH3
0
X
X
X
Off
Off
Off
1
0
0
0
Off
Off
Off
1
1
0
0
On
Off
Off
1
1
1
0
On
On
Off
1
1
1
1
On
On
On
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is a registered trademark of Richtek Technology Corporation.
DS9907-11 May 2014
RT9907
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
COMP3
CH3 Feedback Compensation Pin.
2
VDD3
3
LX3
CH3 Power Input Pin.
CH3 Switch Node. Drains of the internal P-MOSFET and N-MOSFET switches.
Connect an inductor to LX3 pins together as close as possible.
4
PGND3
Power Ground for CH3.
5
SS
Sets the Soft Start interval of the converter. Connect a capacitor from this pin to
ground.
6
RT
Frequency setting resistor connection pin. Frequency is 500kHz if RT pin not
connected
GND
Analog Ground.
8
VDDM
Device Input Power Pin.
9
FB1
CH1 Feedback Input Pin.
10
COMP1
CH1 Feedback Compensation Pin.
11
PGND1
Power Ground for CH1
12
VDD1
CH1 Power Input Pin. Connect output of Boost to this pin.
13
LX1
CH1 Switch Node. Connect an inductor to LX1 Pins together as close as possible.
14
PGND2
15
LX2
Power Ground for CH2.
CH2 Switch Node. Drains of the internal P-Channel and N-MOSFET switches.
Connect an inductor to LX2 pins together as close as possible.
16
VDD2
17
ENM
18
EN1
19
COMP2
CH2 Feedback Compensation Pin.
20
FB2
21
EN2
22
EN3
CH2 Feedback Input.
CH2 Enable Input. Tie this pin higher than 1.3V to enable CH2. Tie below 0.4V to
turn off the CH2.
CH3 Enable Input. Tie this pin higher than 1.3V to enable CH3. Tie below 0.4V to
turn off the CH3.
24
FB3
7, 23
25 (Exposed Pad) GND
CH2 Power Input Pin.
Whole Device Control Pin. Tie this pin higher than 1.3V to enable the device. Tie
below 0.4V to turn off the device.
CH1 Enable Input. Tie this pin higher than 1.3V to enable CH1. Tie below 0.4V to
turn off the CH1.
CH3 Feedback Input.
The exposed pad must be soldered to a large PCB and connected to GND for
maximum power dissipation.
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS9907-11 May 2014
is a registered trademark of Richtek Technology Corporation.
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RT9907
Absolute Maximum Ratings


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(Note 1)
Supply Input Voltage, VDDM, VDD1, VDD2,VDD3 -------------------------------------------------------- −0.3 to 7V
LX1 Pin Switch Voltage ------------------------------------------------------------------------------------------ −0.3V to 7V
LX2 Pin Switch Voltage ------------------------------------------------------------------------------------------ −0.3V to (VDD2 + 0.3V)
LX3 Pin Switch Voltage ------------------------------------------------------------------------------------------ −0.3V to (VDD3 + 0.3V)
Other I/O Pin Voltage --------------------------------------------------------------------------------------------- −0.3V to (VDDM + 0.3V)
Power Dissipation, PD @ TA = 25°C
VQFN-24L 4x4 ----------------------------------------------------------------------------------------------------- 1.85W
Package Thermal Resistance (Note 2)
VQFN-24L 4x4, θJA ------------------------------------------------------------------------------------------------ 54°C/W
Junction Temperature Range ------------------------------------------------------------------------------------ −40°C to 125°C
Lead Temperature (Soldering, 10 sec.) ----------------------------------------------------------------------- 260°C
Operation Temperature Range ---------------------------------------------------------------------------------- −40°C to 85°C
Storage Temperature Range ------------------------------------------------------------------------------------ −65°C to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Mode) -------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ---------------------------------------------------------------------------------------------- 200V
Electrical Characteristics
(VDDM =3.3V, TA = 25°C, Unless Otherwise specification)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
--
1.5
--
V
2.4
--
5.5
V
5.5
V
Supply Voltage
Minimum Startup Voltage (Boost)
V ST
Boost loading < 1mA
VDDM Operating Voltage
V VDDM
VDDM Pin Voltage
VDD1, VDD2, VDD3 Operating
V VDD1
V VDD2 ,
VDD1, VDD2, VDD3 Pin
Voltage
V VDD3
Voltage
VDDM Over Voltage Protection
1.5
--
6.5
--
V
--
0.01
1
uA
--
250
350
uA
--
250
350
uA
--
250
350
uA
Supply Current
Shutdown Supply Current
IOFF
V ENM pin=0V
V VDDM = 3.3V,
CH1 DC/DC Converter
IVDDM
V FB1 = 0.9V
V ENM = 3.3V, VEN1 = 3.3V,
V EN2 = 0V, VEN3 = 0V
V VDDM = 3.3V,
CH2 DC/DC Converter Supply
Current
CH3 DC/DC Converter Supply
Current
IVDDM
IVDDM
V FB2 = 0.9V
V ENM = 3.3V, VEN1 = 0V,
V EN2 = 3.3V, VEN3 = 0V
V VDDM = 3.3V,
V FB3 = 0.9V
V ENM = 3.3V, VEN1 = 0V,
V EN2 = 0V, VEN3 = 3.3V
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is a registered trademark of Richtek Technology Corporation.
DS9907-11 May 2014
RT9907
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Oscillator
Operation Frequency Range
F OSC
475
550
625
kHz
CH1 Maximum Duty Cycle
DMAX1
RT Open
--
85
90
%
CH2 Maximum Duty Cycle
DMAX2
--
--
100
%
CH3 Maximum Duty Cycle
DMAX3
--
--
100
%
0.788
0.8
0.812
V
--
--
12
mV
GM
--
0.2
--
ms
Compensation Source Current
--
22
--
uA
Compensation Sink Current
Power Switch
--
22
--
uA
N-MOSFET
--
300
400
m
VVDD1 = 3.3V
2
2.6
3
A
N-MOSFET, VVDD2 = 3.3V
--
350
450
m
P-MOSFET, VVDD2 = 3.3V
--
350
450
m
1.3
1.5
1.9
A
N-MOSFET, VVDD3 = 3.3V
--
350
450
m
P-MOSFET, VVDD3 = 3.3V
--
350
450
m
1.3
1.5
1.9
A
UVP Threshold Voltage @FB2, FB3
0.3
0.4
0.5
V
Over Voltage Protection @FB2
0.95
1
--
V
VVDDM = 3.3V
--
0.8
1.3
V
VVDDM = 3.3V
0.4
0.8
--
V
140
180
--
C
--
10
--
C
Feedback Voltage (CH1, CH2, CH3)
Feedback Voltage
V FB
Feedback Voltage
︱ΔV FB︱
CH1, CH2, CH3
CH1, CH2, CH3
3.0V < VDDM < 5.5V
Error Amplifier
CH1 On Resistance of MOSFET
RDS(ON)
CH1 Current Limitation
CH2 On Resistance of MOSFET
RDS(ON)
CH2 Current Limitation
CH3 On Resistance of MOSFET
VVDD2 = 3.3V
RDS(ON)
CH3 Current Limitation
VVDD3 = 3.3V
UVP (CH2, CH3) & Over Voltage Protection (CH2)
Control
ENM, EN1, EN2, EN3 Input High
Level Threshold
ENM, EN1, EN2, EN3 Input Low
Level Threshold
Thermal Protection
Thermal Shutdown
T SD
Thermal Shutdown Hysteresis
ΔT SD
Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for
stress ratings. 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 remain possibility to affect device reliability.
Note 2. θ JA is measured in the natural convection at T A = 25°C on a low effective thermal conductivity test board of
JEDEC 51-3 thermal measurement standard.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
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RT9907
Typical Operating Characteristics
Oscillator Ferquency vs. RRT
1800
0.806
1600
Oscillator Frequecny (kHz)
Reference Voltage (V)
Reference Voltage vs. Temperature
0.808
0.804
0.802
0.8
0.798
0.796
0.794
1400
1200
1000
800
600
400
200
0.792
0
-50
-30
-10
10
30
50
70
90
0
100
200
300
Temperature (°C)
Boost Efficiency vs. Output Current
2.5V
80
2V
1.8V
70
60
Boost
VBAT = 2.5V, VDDM = 3.3V, IOUT = 250mA
3.34
Output Voltage (V)
VIN
3V
90
Efficiency (%)
600
Boost Output Voltage vs. VDD1 Voltage
3.345
VOUT = 3.3V
3.335
3.33
3.325
3.32
3.315
3.31
3.305
50
1
10
100
1.5
1000
Output Current (mA)
2
2.5
3
3.5
4
4.5
5
5.5
VDD1 Voltage (V)
Boost Output Voltage vs. VDDM Voltage
Boost Load Transient Response
3.332
Output Voltage
Deviation
(100mV/Div)
VBAT = 2.5V, VDD1 = 3.3V, IOUT = 250mA
3.328
3.326
3.324
3.322
Load Current
(200mA/Div)
Output Voltage (V)
500
RRT (kΩ)
100
3.33
400
3.32
3.318
3.316
2.4
2.8
3.2
3.6
4
4.4
4.8
5.2
5.6
VIN = 1.8V, VOUT = 3.3V, @IOUT = 100mA to 400mA
Time (1ms/Div)
VDDM Voltage (V)
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RT9907
Boost Load Transient Response
VIN = 2.5V, VOUT = 3.3V, @IOUT = 100mA to 400mA
Time (1ms/Div)
Time (1ms/Div)
Boost Load Transient Response
Boost LX & Output Ripple
VIN = 1.8V, VOUT = 3.3V, @IOUT = 100mA
LX1
(2V/Div)
VIN = 3V, VOUT = 3.3V, @IOUT = 100mA to 400mA
Output Ripple
(10mV/Div)
Load Current
(200mA/Div)
Load Current
(200mA/Div)
VIN = 2V, VOUT = 3.3V, @IOUT = 100mA to 400mA
Output Voltage
Deviation
(100mV/Div)
Load Current
(200mA/Div)
Output Voltage
Deviation
(100mV/Div)
Output Voltage
Deviation
(100mV/Div)
Boost Load Transient Response
Time (1ms/Div)
Time (1us/Div)
Boost LX & Output Ripple
Boost LX & Output Ripple
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
Output Ripple
(10mV/Div)
Output Ripple
(10mV/Div)
Time (1us/Div)
DS9907-11 May 2014
VIN = 2.5V, VOUT = 3.3V, @IOUT = 100mA
LX1
(2V/Div)
LX1
(2V/Div)
VIN = 1.8V, VOUT = 3.3V, @IOUT = 300mA
Time (1us/Div)
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RT9907
Boost LX & Output Ripple
Boost LX & Output Ripple
VIN = 3V, VOUT = 3.3V, @IOUT = 100mA
Output Ripple
(10mV/Div)
Output Ripple
(10mV/Div)
LX1
(2V/Div)
LX1
(2V/Div)
VIN = 2.5V, VOUT = 3.3V, @IOUT = 400mA
Time (1us/Div)
Time (1us/Div)
Buck2 Efficiency vs. Output Current
Boost LX & Output Ripple
100
VIN = 3V, VOUT = 3.3V, @IOUT = 400mA
VOUT = 1.5V
VIN = 2.2V
Output Ripple
(10mV/Div)
LX1
(2V/Div)
Efficiency (%)
90
80
VIN = 4.5V
VIN = 2.5V
VIN = 3V
VIN = 3.8V
70
60
50
Time (1us/Div)
1
10
100
1000
Output Current (mA)
Buck2 Efficiency vs. Output Current
100
Buck2 Efficiency vs. Output Current
100
VOUT = 1.8V
VIN = 2.5V
90
VIN = 4.5
80
80
Efficiency (%)
Efficiency (%)
VOUT = 2.5V
90
VIN = 3V
VIN = 4.5 VIN = 3.8V
70
70
60
VIN = 3.8V
50
VIN = 3V
60
40
30
50
1
10
100
Output Current (mA)
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1000
1
10
100
1000
Output Current (mA)
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RT9907
Buck2 Output Voltage vs. VDDM Voltage
Buck2 Output Voltage vs. VDD2 Voltage
1.82
1.82
VDD2 = 3.3V, IOUT = 250mA
1.818
1.816
1.816
Output Voltage (V)
Output Voltage (V)
VBAT = VDDM = 3.3V, IOUT = 250mA
1.818
1.814
1.812
1.81
1.808
1.814
1.812
1.81
1.808
1.806
1.806
1.804
1.804
2
2.5
3
3.5
4
2
4.5
3.5
4
4.5
5
5.5
VDDM Voltage (V)
Buck2 Load Transient Response
Buck2 Load Transient Response
6
@IOUT = 100mA to 400mA
VDD2 = 2.5V, VDDM = 3.3V, VOUT = 1.8V
Load Current
(200mA/Div)
Output Voltage
Deviation
(100mV/Div)
Output Voltage
Deviation
(100mV/Div)
Load Current
(200mA/Div)
3
VDD2 Voltage (V)
@IOUT = 100mA to 400mA
Time (1ms/Div)
VDD2 = 3.8V, VDDM = 3.3V, VOUT = 1.8V
Time (1ms/Div)
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS9907-11 May 2014
Output Voltage
Deviation
(100mV/Div)
Buck2 Load Transient Response
Load Current
(200mA/Div)
Output Voltage
Deviation
(100mV/Div)
@IOUT = 100mA to 400mA
VDD2 = 3V, VDDM = 3.3V, VOUT = 1.8V
Time (1ms/Div)
Buck2 Load Transient Response
Load Current
(200mA/Div)
2.5
@IOUT = 100mA to 400mA
VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V
Time (1ms/Div)
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RT9907
Buck2 LX & Output Ripple
Buck2 LX & Output Ripple
@IOUT = 250mA
Time (500ns/Div)
Buck2 LX & Output Ripple
Buck2 LX & Output Ripple
LX2
(2V/Div)
Output Ripple
(10mV/Div)
@IOUT = 250mA
VDD2 = 3V, VDDM = 3.3V, VOUT = 1.8V
@IOUT = 500mA
VDD2 = 3V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
Time (500ns/Div)
Buck2 LX & Output Ripple
Buck2 LX & Output Ripple
LX2
(2V/Div)
@IOUT = 250mA
VDD2 = 3.8V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
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Output Ripple
(10mV/Div)
Output Ripple
(10mV/Div)
VDD2 = 2.5V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
LX2
(2V/Div)
Output Ripple
(10mV/Div)
Output Ripple
(10mV/Div)
VDD2 = 2.5V, VDDM = 3.3V, VOUT = 1.8V
LX2
(2V/Div)
Output Ripple
(10mV/Div)
LX2
(2V/Div)
LX2
(2V/Div)
@IOUT = 500mA
@IOUT = 500mA
VDD2 = 3.8V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
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DS9907-11 May 2014
RT9907
Buck2 LX & Output Ripple
Output Ripple
(10mV/Div)
Output Ripple
(10mV/Div)
LX2
(2V/Div)
LX2
(2V/Div)
Buck2 LX & Output Ripple
@IOUT = 250mA
VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V
@IOUT = 500mA
VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
Time (500ns/Div)
Buck3 Efficiency vs. Output Current
Buck3 Efficiency vs. Output Current
100
100
VOUT = 1.5V
VOUT = 1.8V
VIN = 2.2V
90
80
Efficiency (%)
Efficiency (%)
90
VIN = 4.5V
VIN = 3V
VIN = 3.8V
70
VIN = 2.5V
80
VIN = 4.5V
VIN = 3.8V VIN = 3V
70
60
60
50
50
1
10
100
1
1000
10
100
1000
Output Current (mA)
Output Current (mA)
Buck3 Efficiency vs. Output Current
Buck3 Output Voltage vs. VDD3 Voltage
100
1.806
VOUT = 2.5V
VBAT = VDDM = 3.3V, IOUT = 250mA
1.804
90
Output Voltage (V)
VIN = 4.5V
80
Efficiency (%)
VIN = 2.5V
70
VIN = 3.8V
60
50
VIN = 3V
40
1.802
1.8
1.798
1.796
1.794
1.792
30
1.79
1
10
100
Output Current (mA)
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS9907-11 May 2014
1000
2
2.5
3
3.5
4
4.5
VDD3 Voltage (V)
is a registered trademark of Richtek Technology Corporation.
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RT9907
Buck3 Output Voltage vs. VDDM Voltage
Buck3 Load Transient Response
1.806
Output Voltage
Deviation
(100mV/Div)
VDD3 = 3.3V, IOUT = 250mA
1.802
1.8
@IOUT = 100mA to 400mA
1.798
1.796
Load Current
(200mA/Div)
Output Voltage (V)
1.804
1.794
1.792
1.79
2
2.5
3
3.5
4
4.5
5
5.5
VDD3 = 2.5V, VDDM = 3.3V, VOUT = 1.8V
6
Time (1ms/Div)
VDDM Voltage (V)
VDD3 = 3V, VDDM = 3.3V, VOUT = 1.8V
Load Current
(200mA/Div)
Load Current
(200mA/Div)
Output Voltage
Deviation
(100mV/Div)
@IOUT = 100mA to 400mA
Buck3 Load Transient Response
Output Voltage
Deviation
(100mV/Div)
Buck3 Load Transient Response
VDD3 = 3.8V, VDDM = 3.3V, VOUT = 1.8V
Time (1ms/Div)
Time (1ms/Div)
Buck3 Load Transient Response
Buck3 LX & Output Ripple
@IOUT = 250mA
VDD3 = 4.5V, VDDM = 3.3V, VOUT = 1.8V
Time (1ms/Div)
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
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Output Ripple
(10mV/Div)
LX3
(2V/Div)
Output Voltage
Deviation
(100mV/Div)
@IOUT = 100mA to 400mA
Load Current
(200mA/Div)
@IOUT = 100mA to 400mA
VDD3 = 2.5V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
is a registered trademark of Richtek Technology Corporation.
DS9907-11 May 2014
RT9907
Buck3 LX & Output Ripple
Buck3 LX & Output Ripple
VDD3 = 2.5V, VDDM = 3.3V, VOUT = 1.8V
@IOUT = 250mA
LX3
Output Ripple
(10mV/Div) (2V/Div)
Output Ripple
(10mV/Div)
LX3
(2V/Div)
@IOUT = 500mA
Time (500ns/Div)
Time (500ns/Div)
Buck3 LX & Output Ripple
Buck3 LX & Output Ripple
@IOUT = 500mA
VDD3 = 3V, VDDM = 3.3V, VOUT = 1.8V
@IOUT = 250mA
LX3
Output Ripple
(10mV/Div) (2V/Div)
LX3
Output Ripple
(10mV/Div) (2V/Div)
VDD3 = 3V, VDDM = 3.3V, VOUT = 1.8V
VDD3 = 3.8V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
Time (500ns/Div)
Buck3 LX & Output Ripple
Buck3 LX & Output Ripple
VDD3 = 3.8V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS9907-11 May 2014
LX3
Output Ripple
(10mV/Div) (2V/Div)
Output Ripple
(10mV/Div)
LX3
(2V/Div)
@IOUT = 500mA
@IOUT = 250mA
VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
is a registered trademark of Richtek Technology Corporation.
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RT9907
Buck3 LX & Output Ripple
Output Ripple
(10mV/Div)
LX3
(2V/Div)
@IOUT = 500mA
VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
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16
is a registered trademark of Richtek Technology Corporation.
DS9907-11 May 2014
RT9907
Application Information
The RT9907 is a three-channel DC/DC converter with one
voltage detector for digital still cameras and other handheld device. The three channels DC/DC converters are as
follows:
CH1: Step-up, asynchronous current mode DC/DC
converter with an internal power MOSFET, current limit
protection and high efficiency control for wide loading
range.
CH2: Step-down, synchronous current mode DC/DC
converter with internal power MOSFETs, current limit,
short-circuit , over voltage protection and high efficiency
control for wide loading range.
CH3: Step-down, synchronous current mode DC/DC
converter with internal power MOSFETs, current limit,
short-circuit protection and high efficiency control for wide
loading range.
Soft-Start
CH1, CH2 and CH3 can be soft-started individually every
time when the channel is enabled. Soft-start is achieved
by ramping up the voltage reference of each channel's input
of error amplifier. Adding a capacitor on SS pin to ground
sets the ramping up speed of each voltage reference.
Triangle wave will be appeared on SS pin, which provides
a clock base for soft-start.
The soft-start timing would
CSSbe setted by following formular.
TSS  10 x
(ms)
1nF
mode. In this mode, the N-MOSFET turns on by a constant
pulse width. As loading increased, the converter operates
at constant frequency PWM mode. The max. duty of the
constant frequency is 80% for the boost to prevent high
input current drawn from input.
Protection
Current limit
The current of NMOS is sensed cycle by cycle to prevent
over current. If the current is higher than 2.6A (typical),
then the NMOS is off . This state is latched and then
reset automatically at next clock cycle.
Under Voltage
The status of under voltage is decided by comparing FB1
voltage with 0.4V. This function is enabled after soft start
finishes. If the FB1 voltage is less than 0.4V, then the
NMOS will be turned off immediately. And this state is
latched. After a dummy count period, the controller begins
a re-soft-start procedure.
If the status of under voltage remains after 4 successive
times of soft-start, then CH1 is latched.
Over Voltage
The over voltage protection is used when the output of
CH1 supplies the power of the main chip. If the output
voltage of CH1 is over 6.5V, the main chip is shutdown
and the N-MOSFET is kept off.
Step-Down (Buck) DC/DC Converter (CH2, CH3)
Oscillator
The internal oscillator synchronizes CH1, CH2 and CH3
PWM operation frequency. The operation frequency is
set by a resistor between RT pin to ground, ranging from
550kHz to 1.4MHz.
Step-up (Boost) DC/DC Converter (CH1)
The step-up channel (CH1) is designed as current-mode
DC/DC PWM converters with built-in internal power MOS
and external Schottky diode. Output voltage is regulated
and adjustable up to 5.5V. This channel typically supplies
3.3V for main system power.
At light load, efficiency is enhanced by pulse-skipping
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS9907-11 May 2014
The step-down channels (CH2, CH3) are designed as
synchronous current-mode DC/DC PWM converters.
Output voltage is regulated and adjustable down to 0.8V.
The internal synchronous power switches eliminate the
typical Schottky free wheeling diode and improve
efficiency.
At light load, efficiency is enhanced by pulse-skipping
mode. In this mode, the high-side P-MOSFET turns on
by a constant pulse width. As loading increased, the
converter operates at constant frequency PWM mode.
While the input voltage is close to output voltage, the
converter enters low dropout mode. Duty could be as long
as 100% to extend battery life.
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RT9907
Protection
Thermal Protection
Current limit (CH2, CH3)
Thermal protection function is integrated in the chip. When
the chip temperature is higher than 180°C, the controllers
of CH1, CH2, and CH3 are shutdown. 10 degree C is the
hysteresis range of temperature to prevent unstable
operation when the thermal protection happens. When
the thermal protection is relieved, the chip operates well
again.
The current of high-side P-MOSFET is sensed cycle by
cycle to prevent over current. If the current is higher than
1.5A (typical), then the high-side P-MOSFET is off and
the low-side N-MOSFET is on. This state is latched and
then reset automatically at next clock cycle.
Under Voltage (CH2, CH3)
The status of under voltage is decided by comparing FB2
(or FB3) voltage with 0.4V. This function is enabled after
soft start finishes. If the FB2 (or FB3) voltage is less than
0.4V, then the high/low-side Power MOS are turned off
immediately. And this state is latched. After a dummy
count period, the CH2 (or CH3) begins a soft-start
procedure.
However, if the status of under voltage remains after 3
successive times of soft-start, then CH2 (or CH3) is
latched.
UV remain after 3
How to reset?
successive soft-start
CH2 CH2 is latched, and whole Toggle ENM
IC is shut down
CH3 CH3 is latched
Toggle EN3 or ENM
Over Voltage Protection (CH2)
Over voltage protection (OVP) is used to protect the
external parts connected to the output of CH2. If the FB2
voltage is higher than 1V, the high-side P-MOSFET is off
and low-side N-MOSFET is on. This status is latched and
could be reset by toggling ENM.
Reference
The chip has an internal 0.8V reference voltage, which is
the inputs of the error amplifiers of the CH1, CH2, and
CH3 to compare the difference of feedback voltage. The
reference voltage can be set up stably when the supplied
power (VDDM) is above 1.5V, and EN1 (or EN2, EN3)
goes high.
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
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is a registered trademark of Richtek Technology Corporation.
DS9907-11 May 2014
RT9907
Outline Dimension
1
1
2
2
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.
Symbol
Dimensions In Millimeters
Dimensions In Inches
Min.
Max.
Min.
Max.
A
0.800
1.000
0.031
0.039
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
3.950
4.050
0.156
0.159
Option 1
2.400
2.500
0.094
0.098
Option 2
2.650
2.750
0.104
0.108
E
3.950
4.050
0.156
0.159
Option 1
2.400
2.500
0.094
0.098
Option 2
2.650
2.750
0.104
0.108
D2
E2
e
L
0.500
0.350
0.020
0.450
0.014
0.018
V-Type 24L QFN 4x4 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.
DS9907-11 May 2014
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