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RT9202
Single Synchronous Buck PWM DC-DC Controller
General Description Features
The RT9202 is a single power supply PWM DC-DC l Operate From 5V
converter controller designed to drive N-Channel l 0.8V Internal Reference
MOSFET in a synchronous buck topology. The IC l Drive Two N-Channel MOSFETs
integrates the control, output adjustment, monitoring and l Voltage Mode PWM Control
protection functions in a small 8-pin package. l Fast Transient Response
l Fixed 300kHz Oscillator Frequency
The RT9202 uses a low gain voltage mode PWM control
l Full 0 to 100% Duty Cycle
for simple application design. An internal 0.8V reference
l Internal Soft Start
allows the output voltage to be precisely regulated to
l Adaptive Non-Overlapping Gate Driver
low voltage requirement. A fixed 300kHz oscillator
l Over-Current Monitor Uses MOSFET RDS(ON)
reduces the component size for saving board space.
l Over-Voltage Protection Uses Low-Side MOSFET
The RT9202 features over current protection, over l RoHS Compliant and 100% Lead (Pb)-Free
voltage protection, and under voltage lock-out. The output
current is monitored by sensing the voltage drop across
Applications
the MOSFET's RDS(ON), which eliminates the need for a
l Motherboard Power Regulation for Computers
current sensing resistor.
l Subsystems Power Supplies
l Cable Modems, Set Top Box, and DSL Modems
Ordering Information
l DSP and Core Communications processor Supplies
RT9202
l Memory Power Supplies
l Personal Computer Peripherals
Package Type l Industrial Power Supplies
S : SOP-8
l 5V-Input DC-DC Regulators
Operating Temperature Range l Low Voltage Distributed Power Supplies
C : Commercial Standard
P : Pb Free with Commercial Standard
Pin Configurations
Note :
RichTek Pb-free products are :
(TOP VIEW)
-RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020. BOOT 8 PHASE
UGATE 2 7 OCSET
-Suitable for use in SnPb or Pb-free soldering processes.
GND 3 6 FB
-100%matte tin (Sn) plating.
LGATE 4 5 VCC
SOP-8
DS9202-06 March 2005 www.richtek.com
1
RT9202
Typical Application Circuit
R1
5V
20K R4 10
D1
C2 MA732
8 1
PHASE BOOT
0.1uF
7 2
OCSET UGATE MU
VOUT L2
Q1
+
SHND 2N7002 2.5V C5 C1
6 3
+
H : shutdown FB GND 5uH 1uF 470uF
C3
5 4 1000uF
VCC LGATE
C4 RT9202
1uF ML
R3 R2
120 255
C6
10nF
Figure 1. RT9202 powered from 5V only
R4
12V
R1 10
5V
20K
C2
8 1 1uF
PHASE BOOT
7 2
OCSET UGATE MU
VOUT L1
Q1
+
SHND 2.5V C5 C1
2N7002 6 3
+
H : shutdown FB GND 5uH 1uF 470uF
5V C3
5 4 1000uF
VCC LGATE
RT9202
C4 ML
1uF
R3 R2
120 250
C6
10nF
Figure 2. RT9202 powered from 12V and 5V
www.richtek.com DS9202-06 March 2005
2
RT9202
MU
+
COUT D
1000uF L
5uH G S
+
CIN1 CIN2
GND 1uF 470uF
CVCC CBOOT
1uF ML
BOOT
VCC
0.1uF D
RT9202
G S
GND Return
Layout Placement
Layout Notes
1. Put CIN1 & CIN2 to be near the MU drain and ML source nodes.
2. Put RT9202 to be near the COUT
3. Put CBOOT as close as to BOOT pin
4. Put CVCC as close as to VCC pin
Function Block Diagram
6.0V
VCC BOOT
Regulation
Power on
Bias
Reset
0.8 40uA
Soft Start
Reference
+ OCSET
OC
-
1.1V -
OVP UGATE
+
-
0.5V UVP
+ Control PHASE
0.8V Logic
+
Error + VCC
FB - Error PWM
-
Amplifier
LGATE
GND 300kHz
Oscillator
DS9202-06 March 2005 www.richtek.com
3
RT9202
Functional Pin Description
BOOT (Pin 1) OCSET (Pin 7)
This pin provides ground referenced bias voltage to the Connect a resistor from this pin to the drain of the upper
upper MOSFET driver. A bootstrap circuit is used to MOSFET. This resistor, an internal 40