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Preliminary
RT9902
4 Channel DC/DC Converters IC with High-Efficiency Step-Up and Step-Down
General Description
The RT9902 is a complete power supply solution for digital still cameras and other hand-held devices. It integrates a high-efficiency main step-up DC-DC converter, two highefficiency step-down converters, a charge pump, and a linear controller that drives an external P-MOSFET for linear regulator. The RT9902 is targeted for applications that use either two or three AA cells or a single lithiumion battery. The main step-up DC-DC converter accepts inputs from 1.5V to 5.5V and build in 2.6A Internal switch. The two step-down DC-DC converters (CH2, CH3) accept inputs from 1.5V to 5.5V and regulate a resistor adjustable output from 0.8V to 5.5V. Each DC-DC converter has independent shutdown input. The feature of the charge pump is to deliver few current to micro-controller when the system operates in the standby mode. RT9902 includes a linear controller with 0.8V reference voltage. An adjustable operating frequency (up to 1.4MHz) is utilized to get optimum size, cost, and efficiency. RT9902 is available in VQFN-32L 5x5 package.
Features
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, 0.3 Internal Power Switch Two Step-Down DC-DC Converters 0.8V to 5.5V Adjustable Output Voltage 94% Efficiency 100% Duty Cycle Step-up Charge Pump for Micro-Controller Linear Controller for Linear Regulator Up to 1.4MHz Switching Frequency 1A 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) 32-Lead VQFN Package RoHS Compliant and 100% Lead (Pb)-Free
Applications
Digital Still Cameras PDAs Portable Devices
Ordering Information
RT9902 Package Type QV : VQFN-32L 5x5 (V-Type) Operating Temperature Range P : Pb Free with Commercial Standard G : Green (Halogen Free with Commercial Standard)
Pin Configurations
(TOP VIEW)
COMP2 ENM
25 24 23 22
GND
EN3
EN2
Note : Richtek Pb-free and Green products are : RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. 100% matte tin (Sn) plating.
COMP3 VDD3 LX3 PGND3 SS RT GND LDO_O
1 2 3 4 5 6 7 8
32 31
30 29 28
27 26
EN1
FB3
FB2
VDD2 VDD2 LX2 LX2 PGND2 LX1 LX1 VDD1
GND
21 20 19 33 18 17
9
10
11 12 13
14 15
16
COMP1
VQFN-32L 5x5 DS9902-10 August 2007 www.richtek.com 1
PGND1
FB1
VDDC
LFB
VDDM
CPFB
CX
RT9902
Typical Application Circuit
1-cell Li+ Battery 3V to 4.2V
Preliminary
V BAT C12 1F 9 V BAT 1.5V/500mA C3 to C6 10F x 4 R1 200k R2 220k C7 100pF V BAT C8 10F IGBT Driver 5V/50mA C9 to C10 10F x 2 R3 680k R4 130k Chip Enable D1 SS0520 C12 C1 to C2 10F x 2 VDD3 LX3 L1 4.7H VDDM 2
C17 C18 10F 10F
L2 4.7H C19 0.1F
3 32 14
LX1 18 19 17 R9 510k R10 150k 8
D3 SS0520
FB3 VDDC
VDD1
C20 100pF
C21 to C24 10F x 4 R11 51k Q1 SI2301 C26 10F V IN 3.52V V OUT 3.3V/500mA
11 FB1 RT9902 LDO_O
15 D2 C11 SS0520 22nF 1nF 13 25 26 29 30 R5 R6 20k 30k
CX CPFB ENM EN1 EN2 EN3
LFB VDD2
10 23 24 L3 4.7H
C25 100pF
R12 470k R13 150k
C27 to C28 10F x 2
12 COMP1 27 COMP2 1 COMP3
V BAT C29 to C30 10F x 2
21 LX2 22
2.5V/500mA R14 470k C32 to C35 10F x 4 R15 220k
C13 4.7nF
C14 1nF C15 1nF
R7 30k
C31 100pF FB2 28 PGND2 PGND1
PGND3
C16 1nF
6 R8
4
20 16
Figure 1. Typical Application Circuit from 1-cell Li+ Battery
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GND 7, 31 Exposed Pad (33)
5 SS RT
DS9902-10 August 2007
Preliminary
1-cell Li+ Battery 3.4V to 4.2V
RT9902
V BAT C12 1F 9 V BAT 1.5V/500mA C3 to C6 10F x 4 R1 200k R2 220k C7 100pF V BAT C8 10F IGBT Driver 5V/50mA C9 to C10 10F x 2 R3 680k R4 130k Chip Enable C11 1nF D1 SS0520 C12 C1 to C2 10F x 2 VDD3 LX3 L1 4.7H VDDM 2
C17 C18 10F 10F
L2 4.7H C19 0.1F 5V/500mA RT9701CB 5 VIN VOUT 4 EN VOUT 1 Chip Enable GND 10uF 2 3
3 32 14
LX1 18 19 17
D3 SS0520 C20 100pF R11 51k
FB3 VDDC
VDD1
11 FB1 RT9902 LDO_O 8
R9 680k R10 130k
C21 to C24 10F x 4
15
D2 22nF SS0520 13 25 26 29 30 R5 20k
CX CPFB ENM EN1 EN2 EN3
Q1 SI2301 C25 100pF R12 470k R13 150k
LFB VDD2
10 23 24 L3 4.7H C31 100pF
V IN C26 10F V OUT C27 to C28 10F x 2
12 COMP1 27 COMP2 1 COMP3
V BAT C29 to C30 10F x 2
R6 30k C14 1nF C15 1nF C16 1nF R7 30k
21 LX2 22
3.3V/500mA R14 470k C32 to C35 10F x 4 R15 150k
C13 4.7nF
FB2 PGND3 PGND2 PGND1 GND 5 SS RT
28
6 R8
4
20 16
7, 31 Exposed Pad (33)
Figure 2. Typical Application Circuit from 1-cell Li+ Battery
DS9902-10 August 2007
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RT9902
2-AA Battery 2.0V to 3.4V
Preliminary
C16 1F 9 V BAT 1.5V/300mA C3 to C6 10F x 4 R1 200k R2 220k C7 100pF V BAT C8 10F C standby 3.3V/1mA C9 10F 15 D2 SS0520 10nF 13 25 Chip Enable 26 29 30 R5 20k R6 30k C13 1nF C14 1nF C15 1nF R7 30k 12 27 C11 D1 SS0520 C1 to C2 10F x 2 VDD3 LX3 FB3 VDDC FB1 CX CPFB ENM EN1 EN2 EN3 COMP1 LX2 COMP2 LFB VDD2 10 23 24 L3 4.7H C30 100pF FB2 PGND3 PGND2 PGND1 GND 5 SS RT 28 R15 220k RT9902 LDO_O 8 C24 100pF 11 VDDM 2 L1 4.7H L2 4.7H D3 SS0520
3 32 14
LX1 18 19 17
V BAT C17 to C18 10F x 2 I/O 3.3V/500mA
VDD1
R9 470k R10 150k
C19 100pF R11
C20 to C23 10F x 4
R3 47k R4 15k
C10 1nF
Q1 SI2301 R12 470k R13 150k C28 to C29 10F x 2
C25 10F
V IN
V OUT C26 to C27 10F x 2
3.3V
21 22
2.5V/300mA R14 470k C31 to C34 10F x 4
C12 4.7nF
1 COMP3
6 R8
4
20 16
7, 31 Exposed Pad (33)
Figure 3. Typical Application Circuit from 2-AA Battery Supply
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DS9902-10 August 2007
Preliminary Function Block Diagram
RT9902
VDDM
ENM
VDDC CX CPFB LDO_O
CH4 Charge Pump
EN CH1 Current-MODE Asynchronous Step-Up PWM Boost
EN1 VDD1 LX1
PGND1 COMP1 FB1 EN2 VDD2 LX2 PGND2 COMP2 FB2 EN3 VDD3 LX3 PGND3 COMP3 FB3
LFB
Linear Controller
EN
SS
Soft-Start OSC
CH2 Current-MODE Synchronous Step-Down PWM Buck2
RT
PWM OSC
Thermal Shutdown
CH3 Current-MODE Synchronous Step-Down PWM Buck3
GND
ENM 0 1 1 1 1
EN1 X 0 1 1 1
EN2 X 0 0 1 1
EN3 X 0 0 0 1
Charge Pump Off On On On On
CH1 + Linear Controller Off Off On On On
CH2 Off Off Off On On
CH3 Off Off Off Off On
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RT9902
Functional Pin Description
Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18, 19 20 21, 22 23, 24 25 26 27 28 29 30 31 32 Pin Name COMP3 VDD3 LX3 PGND3 SS RT GND LDO_O VDDM LFB FB1 COMP1 CPFB VDDC CX PGND1 VDD1 LX1 PGND2 LX2 VDD2 ENM EN1 COMP2 FB2 EN2 EN3 GND FB3
Preliminary
Pin Function CH3 Feedback Compensation Pin. CH3 Power Input Pin. CH3 Switch Node. Drains of the internal P-Channel and N-MOSFET switches. Connect an inductor to LX3 pins together as close as possible. Power Ground for CH3. Sets the soft start interval of the converter. Connect a capacitor from this pin to ground. Frequency Setting Resistor Connection Pin. Frequency is 500kHz if RT pin not connected. Analog Ground. Linear Controller Driver Output. Device Input Power Pin. Linear Controller Feedback Input. CH1 Feedback Input Pin. CH1 Feedback Compensation Pin. Charge Pump Feedback Pin. Charge Pump Power Input Pin. Charge Pump External Driver Pin. Power Ground for CH1. CH1 Power Input Pin. Connect output of Boost to this pin. CH1 Switch Node. Connect an inductor to LX1 pins together as close as possible. Power Ground for CH2. CH2 Switch Node. Drains of the internal P-MOSFET and N-MOSFET switches. Connect an inductor to LX2 pins together as close as possible. 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. CH2 Feedback Compensation Pin. 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. Analog Ground. CH3 Feedback Input. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation.
Exposed Pad (33) GND
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Preliminary Absolute Maximum Ratings
RT9902
Supply Input Voltage (VDDM, VDD1, VDD2,VDD3,VDDC) ----------------------------------------------------- -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) CX Pin Switch Voltage ------------------------------------------------------------------------------------------ -0.3V to (VDDC + 0.3V) Other I/O Pin Voltage -------------------------------------------------------------------------------------------- -0.3V to (VDDM + 0.3V) Package Thermal Resistance VQFN-32L 5x5, JA ----------------------------------------------------------------------------------------------- 34C/W Lead Temperature (Soldering, 10 sec.) ---------------------------------------------------------------------- 260C Operation Temperature Range --------------------------------------------------------------------------------- -40C to 85C Junction Temperature Range ----------------------------------------------------------------------------------- 0C to 125C Storage Temperature Range ----------------------------------------------------------------------------------- -65C to 150C ESD Susceptibility HBM (Human Body Mode) ------------------------------------------------------------------------------------- 2kV MM (Machine Mode) --------------------------------------------------------------------------------------------- 200V
Electrical Characteristics
(VDDM =3.3V, TA = 25C, Unless Otherwise specification)
Parameter Supply Voltage Minimum Startup Voltage (Boost) VDDM Operating Voltage VDD1, VDD2, VDD3 Operating Voltage VDDM Over Voltage Protection Supply Current Shutdown Supply Current Charge Pump Current
Symbol VST VVDDM VVDD1 VVDD2, VVDD3
Test Condition Boost loading < 1mA VDDM Pin Voltage VDD1, VDD2, VDD3 Pin Voltage
Min -2.4 1.5 --
Typ 1.5 --
Max -5.5 5.5
Units V V V V A A
6.5 0.01 30
-1 42
IOFF IVDDM
VENM pin=0V VVDDM = 3.3V, VENM = 3.3V, VEN1 = 0V, VEN2 = 0V, VEN3 = 0V VVDDM = 3.3V,
---
CH1 DC/DC Converter + Linear Controller Supply Current
IVDDM
VFB1 = 0.9V VENM = 3.3V, VEN1 = 3.3V, VEN2 = 0V, VEN3 = 0V VVDDM = 3.3V,
--
250
350
A
CH2 DC/DC Converter Supply Current
IVDDM
VFB2 = 0.9V VENM = 3.3V, VEN1 = 0V, VEN2 = 3.3V, VEN3 = 0V VVDDM = 3.3V,
--
250
350
A
CH3 DC/DC Converter Supply Current
IVDDM
VFB3 = 0.9V VENM = 3.3V, VEN1 = 0V, VEN2 = 0V, VEN3 = 3.3V
--
250
350
A
To be continued
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RT9902
Parameter Oscillator Operation Frequency Range CH1 Maximum Duty Cycle CH2 Maximum Duty Cycle CH3 Maximum Duty Cycle Feedback Voltage Feedback Voltage Feedback Voltage Error Amplifier GM Compensation Source Current Compensation Sink Current Power Switch CH1 On Resistance of MOSFET CH1 Current Limitation CH2 On Resistance of MOSFET CH2 Current Limitation CH3 On Resistance of MOSFET CH3 Current Limitation Linear Controller Feedback Voltage for Linear Controller LDO_O pin Sink Current UVP Threshold Voltage @FB2, FB3 Over Voltage Protection @FB2 Control ENM, EN1, EN2, EN3 Input High Level Threshold ENM, EN1, EN2, EN3 Input Low Level Threshold Thermal Protection Thermal Shutdown Thermal Shutdown Hysteresis TSD TSD VLFB RDS(ON) RDS(ON) RDS(ON) FOSC DMAX1 DMAX2 DMAX3 VFB VCPFB VFB Symbol
Preliminary
Test Condition RT Open Min 475 ---CH1, CH2, CH3 CH4 CH1, CH2, CH3, CH4 3.0V < VDDM < 5.5V 0.788 0.78 -Typ 550 85 --0.8 0.8 -Max 625 90 100 100 0.812 0.82 12 Units kHz % % % V V
mV
Feedback Voltage (CH1, CH2, CH3, CH4)
(Charge Pump)
---N-MOSFET VVDD1 = 3.3V N-MOSFET, VVDD2 = 3.3V P-MOSFET, VVDD2 = 3.3V VVDD2 = 3.3V N-MOSFET, VVDD3 = 3.3V P-MOSFET, VVDD3 = 3.3V VVDD3 = 3.3V -2 --1.3 --1.3
0.2 22 22 300 2.6 350 350 1.5 350 350 1.5
---400 3 450 450 1.9 450 450 1.9
ms A A m A m m A m m A
0.774 VLDO_O = 1V 110 0.3 0.95 VVDDM = 3.3V VVDDM = 3.3V -0.4
0.79 150 0.4 1 0.8 0.8
0.806 -0.5 -1.3 --
V A V V V V C C
UVP (CH2, CH3) & Over Voltage Protection (CH2)
140 --
180 10
---
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Preliminary Typical Operating Characteristics
Reference Voltage vs. Temperature
0.808
RT9902
Oscillator Ferquency vs. RRT
1800
Oscillator Frequecny (kHz)
-50 -30 -10 10 30 50 70 90
0.806
1600 1400 1200 1000 800 600 400 200 0 0 100 200 300 400 500 600
Reference Voltage (V)
0.804 0.802 0.8 0.798 0.796 0.794 0.792
Temperature (C)
RRT (k)
Boost Efficiency vs. Output Current
100
Boost Output Voltage vs. VDD1 Voltage
3.345
VOUT = 3.3V
90
VBAT = 2.5V, VDDM = 3.3V, IOUT = 250mA VIN 3V 2.5V
3.34 3.335 3.33 3.325 3.32 3.315 3.31
80
2V 1.8V
70
60
Boost
50 1 10 100 1000
Output Voltage (V)
Efficiency (%)
3.305 1.5 2 2.5 3 3.5 4 4.5 5 5.5
Output Current (mA)
VDD1 Voltage (V)
Output Voltage vs. VDDM Voltage
3.332 3.33
Boost Load Transient Response
Output Voltage Deviation (100mV/Div) Load Current (200mA/Div)
VIN = 1.8V, VOUT = 3.3V, @IOUT = 100mA to 400mA
VBAT = 2.5V, VDD1 = 3.3V, IOUT = 250mA
Output Voltage (V)
3.328 3.326 3.324 3.322 3.32 3.318 3.316 2.4 2.8 3.2 3.6 4 4.4 4.8 5.2 5.6
Time (1ms/Div)
VDDM Voltage (V)
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RT9902
Preliminary
Boost Load Transient Response
Output Voltage Deviation (100mV/Div) Output Voltage Deviation (100mV/Div)
Boost Load Transient Response
Load Current (200mA/Div)
Load Current (200mA/Div)
VIN = 2V, VOUT = 3.3V, @IOUT = 100mA to 400mA
VIN = 2.5V, VOUT = 3.3V, @IOUT = 100mA to 400mA
Time (1ms/Div)
Time (1ms/Div)
Boost Load Transient Response
Output Voltage Deviation (100mV/Div)
Boost LX & Output Ripple
VIN = 1.8V, VOUT = 3.3V, @IOUT = 100mA
Load Current (200mA/Div)
VIN = 3V, VOUT = 3.3V, @IOUT = 100mA to 400mA
Time (1ms/Div)
Output Ripple (10mV/Div)
LX1 (2V/Div)
Time (1us/Div)
Boost LX & Output Ripple
VIN = 1.8V, VOUT = 3.3V, @IOUT = 300mA
Boost LX & Output Ripple
VIN = 2.5V, VOUT = 3.3V, @IOUT = 100mA
LX1 (2V/Div)
Output Ripple (20mV/Div)
Time (1us/Div)
Output Ripple (10mV/Div)
LX1 (2V/Div)
Time (1us/Div)
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DS9902-10 August 2007
Preliminary
RT9902
Boost LX & Output Ripple
VIN = 3V, VOUT = 3.3V, @IOUT = 100mA
Boost LX & Output Ripple
VIN = 2.5V, VOUT = 3.3V, @IOUT = 400mA
LX1 (2V/Div)
Output Ripple (20mV/Div)
Time (1us/Div)
Output Ripple (10mV/Div)
LX1 (2V/Div)
Time (1us/Div)
Boost LX & Output Ripple
VIN = 3V, VOUT = 3.3V, @IOUT = 400mA
Buck2 Efficiency vs. Output Current
100
VOUT = 1.5V VIN = 2.2V
90
Efficiency (%)
LX1 (2V/Div)
80
VIN = 4.5V
70
VIN = 2.5V
Output Ripple (10mV/Div)
VIN = 3V VIN = 3.8V
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
VOUT = 2.5V VIN = 4.5
90
90 80
Efficiency (%)
80
VIN = 4.5 VIN = 3.8V
VIN = 3V
Efficiency (%)
70 60 50
70
VIN = 3.8V VIN = 3V
60
40 30
50 1 10 100 1000
1
10
100
1000
Output Current (mA)
Output Current (mA)
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RT9902
Preliminary
Buck2 Output Voltage vs. VDD2 Voltage
1.82
1.82
Buck2 Output Voltage vs. VDDM Voltage
VDD2 = 3.3V, IOUT = 250mA
1.818
VBAT = VDDM = 3.3V, IOUT = 250mA
1.818 1.816 1.814 1.812 1.81 1.808 1.806 1.804 2 2.5 3 3.5 4 4.5
1.816 1.814 1.812 1.81 1.808 1.806 1.804 2
Output Voltage (V)
Output Voltage (V)
2.5
3
3.5
4
4.5
5
5.5
6
VDD2 Voltage (V)
VDDM Voltage (V)
Buck2 Load Transient Response
@IOUT = 100mA to 400mA
Buck2 Load Transient Response
@IOUT = 100mA to 400mA
Output Voltage Deviation (100mV/Div)
Load Current (200mA/Div)
VDD2 = 2.5V, VDDM = 3.3V, VOUT = 1.8V
Load Current (200mA/Div)
Output Voltage Deviation (100mV/Div)
VDD2 = 3V, VDDM = 3.3V, VOUT = 1.8V
Time (1ms/Div)
Time (1ms/Div)
Buck2 Load Transient Response
Output Voltage Deviation (100mV/Div) Output Voltage Deviation (100mV/Div)
@IOUT = 100mA to 400mA
Buck2 Load Transient Response
@IOUT = 100mA to 400mA
Load Current (200mA/Div)
VDD2 = 3.8V, VDDM = 3.3V, VOUT = 1.8V
Load Current (200mA/Div)
VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V
Time (1ms/Div)
Time (1ms/Div)
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DS9902-10 August 2007
Preliminary
RT9902
Buck2 LX & Output Ripple
@IOUT = 250mA
Buck2 LX & Output Ripple
@IOUT = 500mA
LX2 (2V/Div)
Output Ripple (10mV/Div)
Output Ripple (10mV/Div)
LX2 (2V/Div)
VDD2 = 2.5V, VDDM = 3.3V, VOUT = 1.8V VDD2 = 2.5V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
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
Output Ripple (10mV/Div)
LX2 (2V/Div)
@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)
Output Ripple (10mV/Div)
@IOUT = 250mA VDD2 = 3.8V, VDDM = 3.3V, VOUT = 1.8V
Output Ripple (10mV/Div)
LX2 (2V/Div)
@IOUT = 500mA VDD2 = 3.8V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
Time (500ns/Div)
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RT9902
Buck2 LX & Output Ripple
Preliminary
Buck2 LX & Output Ripple
LX2 (2V/Div)
Output Ripple (10mV/Div)
@IOUT = 250mA VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V
Output Ripple (10mV/Div)
LX2 (2V/Div)
@IOUT = 500mA VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
Time (500ns/Div)
Buck3 Efficiency vs. Output Current
100
Buck3 Efficiency vs. Output Current
100
VOUT = 1.5V
VIN = 2.2V
90
VOUT = 1.8V
VIN = 2.5V
90
Efficiency (%)
Efficiency (%)
80
VIN = 4.5V VIN = 3V VIN = 3.8V VIN = 2.5V
80
VIN = 4.5V VIN = 3.8V VIN = 3V
70
70
60
60
50 1 10 100 1000
50 1 10 100 1000
Output Current (mA)
Output Current (mA)
Buck3 Efficiency vs. Output Current
100
Buck3 Output Voltage vs. VDD3 Voltage
1.806
VOUT = 2.5V
90
VBAT = VDDM = 3.3V, IOUT = 250mA
1.804
VIN = 4.5V
Output Voltage (V)
100 1000
80
1.802 1.8 1.798 1.796 1.794 1.792 1.79
Efficiency (%)
70
VIN = 3.8V
60 50 40 30 1 10
VIN = 3V
2
2.5
3
3.5
4
4.5
Output Current (mA)
VDD3 Voltage (V)
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DS9902-10 August 2007
Preliminary
RT9902
Buck3 Load Transient Response
Buck3 Output Voltage vs. VDDM Voltage
1.806 1.804
Output Voltage (V)
1.802 1.8 1.798 1.796 1.794 1.792 1.79 2 2.5 3 3.5 4 4.5 5 5.5 6
Load Current (200mA/Div)
Output Voltage Deviation (100mV/Div)
VDD3 = 3.3V, IOUT = 250mA
@IOUT = 100mA to 400mA
VDD3 = 2.5V, VDDM = 3.3V, VOUT = 1.8V
Time (1ms/Div)
VDDM Voltage (V)
Buck3 Load Transient Response
Output Voltage Deviation (100mV/Div) Output Voltage Deviation (100mV/Div)
@IOUT = 100mA to 400mA
Buck3 Load Transient Response
@IOUT = 100mA to 400mA
Load Current (200mA/Div)
VDD3 = 3V, VDDM = 3.3V, VOUT = 1.8V
Load Current (200mA/Div)
VDD3 = 3.8V, VDDM = 3.3V, VOUT = 1.8V
Time (1ms/Div)
Time (1ms/Div)
Buck3 Load Transient Response
@IOUT = 100mA to 400mA
Buck3 LX & Output Ripple
@IOUT = 250mA
Output Voltage Deviation (100mV/Div)
Load Current (200mA/Div)
VDD3 = 4.5V, VDDM = 3.3V, VOUT = 1.8V
Output Ripple (10mV/Div)
LX3 (2V/Div)
VDD3 = 2.5V, VDDM = 3.3V, VOUT = 1.8V
Time (1ms/Div)
Time (500ns/Div)
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RT9902
Buck3 LX & Output Ripple
@IOUT = 500mA
Preliminary
Buck3 LX & Output Ripple
@IOUT = 250mA
LX3 (2V/Div)
Output Ripple (10mV/Div)
VDD3 = 2.5V, VDDM = 3.3V, VOUT = 1.8V
LX3 Output Ripple (10mV/Div) (2V/Div)
VDD3 = 3V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
Time (500ns/Div)
Buck3 LX & Output Ripple
@IOUT = 500mA
Buck3 LX & Output Ripple
@IOUT = 250mA
LX3 Output Ripple (2V/Div) (10mV/Div)
VDD3 = 3V, VDDM = 3.3V, VOUT = 1.8V
LX3 Output Ripple (10mV/Div) (2V/Div)
VDD3 = 3.8V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
Time (500ns/Div)
Buck3 LX & Output Ripple
@IOUT = 500mA
Buck3 LX & Output Ripple
LX3 (2V/Div)
Output Ripple (10mV/Div)
LX3 Output Ripple (10mV/Div) (2V/Div)
VDD3 = 3.8V, VDDM = 3.3V, VOUT = 1.8V
@IOUT = 250mA VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
Time (500ns/Div)
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DS9902-10 August 2007
Preliminary
RT9902
Charge Pump CX & Output Ripple
@IOUT = 1mA
Buck3 LX & Output Ripple
@IOUT = 500mA
VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V
Output Ripple Charge Pump (5mV/Div) (2V/Div)
Output Ripple (10mV/Div)
LX3 (2V/Div)
VIN = 2V, VDDM = 3.3V, VOUT = 3.3V
Time (500ns/Div)
Time (5us/Div)
Charge Pump CX & Output Ripple
@IOUT = 1mA
Linear Controller Load Transient Response
Output Voltage Deviation (mV)
VIN = 3.5V, VOUT = 3.3V 20 TA = 25C 0 -20
Output Ripple Charge Pump (5mV/Div) (2V/Div)
400 200 0
VIN = 2.5V, VDDM = 3.3V, VOUT = 3.3V
Time (25us/Div)
Load Current (mA)
Time (1ms/Div)
Linear Controller Load Transient Response
Output Voltage Deviation (mV)
VIN = 3.8V, VOUT = 3.3V 20 TA = 25C 0 -20
Linear Controller Load Transient Response
Output Voltage Deviation (mV)
VIN = 4.2V, VOUT = 3.3V 10 TA = 25C 0 -10
400 200 0
400 200 0
Load Current (mA)
Load Current (mA)
Time (1ms/Div)
Time (1ms/Div)
DS9902-10 August 2007
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RT9902
Preliminary
Boost Series Linear Controller Load Transient Response
Output Voltage Deviation (mV)
VIN = 3V, VOUT = 3.3V 10 TA = 25C 0 -10
Boost Series Linear Controller Load Transient Response
Output Voltage Deviation (mV)
VIN = 3.3V, VOUT = 3.3V 10 TA = 25C 0 -10
400 200 0
400 200 0
Load Current (mA)
Time (1ms/Div)
Load Current (mA)
Time (1ms/Div)
Boost Series Linear Controller Load Transient Response
Output Voltage Deviation (mV)
VIN = 4.2V, VOUT = 3.3V 10 TA = 25C 0 -10
400 200 0
Load Current (mA)
Time (1ms/Div)
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DS9902-10 August 2007
Preliminary Application Information
The RT9902 is a four-channel DC/DC converter with one linear controller for digital still cameras and other handheld device. The four 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. CH4: Charge pump DC/DC converter. 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 be setted by following formular.
TSS = 10 x CSS 1nF (ms)
RT9902
At light load, efficiency is enhanced by pulse-skipping mode. In this mode, the NMOS turns on by a constant pulse width. As loading increased, the converter operates at constant frequency PWM mode. The maximum 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 NMOS is kept off. Step-Down (Buck) DC/DC Converter (CH2, CH3) 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 PMOS 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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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.
DS9902-10 August 2007
RT9902
Protection
Current Limit (CH2, CH3)
Preliminary
IMAX = 2 x (VDDC-VF) x CCP x FCP VF : Schottky diode forward voltage Fpump : Charge pump maximum frequency is 500kHz Recommand CCP 0.1F.
The current of high-side PMOS is sensed cycle by cycle to prevent over current. If the current is higher than 1.5A (typical), then the high-side PMOS is off and the low-side NMOS 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
VDDC CX CCP CPFB GND
VBAT
R1 R2
CX COUT
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. Thermal Protection Thermal protection function is integrated in the chip. When the chip temperature is higher than 178 C, the controllers of CH1, CH2, and CH3 are shutdown. 10C 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.
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 PMOS is off and low-side NMOS is on. This status is latched and could be reset by toggling ENM. Charge Pump DC/DC Converter This is a low quiescent charge pump DC/DC converter, which is enabled by ENM. Add a capacitor CX (~1nF) between charge pump VOUT and CPFB to speed up charge pump response time. Output ripple can be easily suppressed by increasing the capacitance ratio of COUT and CCP. This charge pump DC/DC converter can apply to C stanby power or the gate driver power of IGBT for photoflash, etc. The maximum output current can be determined by CCP and C OUT ration. This equation would describe the relationship.
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DS9902-10 August 2007
Preliminary Outline Dimension
RT9902
D
D2
SEE DETAIL A L
1
E
E2
e
b
1 2
1 2
A A1 A3
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 A A1 A3 b D D2 E E2 e L
Dimensions In Millimeters Min 0.800 0.000 0.175 0.180 4.950 3.400 4.950 3.400 0.500 0.350 0.450 Max 1.000 0.050 0.250 0.300 5.050 3.750 5.050 3.750
Dimensions In Inches Min 0.031 0.000 0.007 0.007 0.195 0.134 0.195 0.134 0.020 0.014 0.018 Max 0.039 0.002 0.010 0.012 0.199 0.148 0.199 0.148
V-Type 32L QFN 5x5 Package
Richtek Technology Corporation
Headquarter 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611
Richtek Technology Corporation
Taipei Office (Marketing) 8F, No. 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek.com
DS9902-10 August 2007
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