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RT9202CS

Single Synchronous Buck PWM DC-DC Controller

Richtek Technology 

RT9202

Parameter

Protection

FB Over-Voltage Trip

FB Under-Voltage Trip

OCSET Current Source

Soft-Start Interval

Symbol

Test Conditions

IOCSET

FB Rising

FB Falling

VOCSET= 4.5V

Min Typ Max Units

1.0 1.1 --

V

-- 0.5 0.6 V

35 40 45 µA

1

2

4 mS

Functional Pin Description

BOOT (Pin 1)

This pin provides ground referenced bias voltage to the

upper MOSFET driver. A bootstrap circuit is used to

create a voltage suitable to drive a logic-level N-

channel MOSFET when operating at a single 5V power

supply. This pin also could be powered from ATX 12V,

in this situation, a internal 6.0V regulator will supply to

VCC pin for internal voltage bias.

UGATE (Pin 2)

Connect UGATE pin to the PWM converter’s upper

MOSFET gate. This pin provides the gate drive for the

upper MOSFET.

GND (Pin 3)

Signal and power ground for the IC. All voltage levels

are measured with respect to this pin.

LGATE (Pin 4)

Connect LGATE to the PWM converter’s lower

MOSFET gate. This pin provides the gate drive for the

lower MOSFET.

VCC (Pin 5)

This is the main bias supply for the RT9202. This pin

also provides the gate bias charge for the lower

MOSFETs gate. The voltage at this pin monitored for

power-on reset (POR) purpose. This pin is also the

internal 6.0V regulator output powered from BOOT pin

when BOOT pin is directly powered from ATX 12V.

FB (Pin 6)

This pin is connected to the PWM converter’s output

divider. This pin also connects to internal PWM error

amplifier inverting input and protection monitor.

OCSET (Pin 7)

Connect a resistor from this pin to the drain of the

respective upper MOSFET. This resistor, an internal

40µA current source, and the upper MOSFET on-

resistance set the converter over-current trip point. An

over-current trip cycles the soft-start function. The

voltage at this pin is monitored for power-on reset

(POR) purpose and pulling this pin low with an open

drain device will shut down the IC.

IPEAK = IOCSET × ROCSET

RDS(ON)

PHASE (Pin 8)

This pin is used to monitor the voltage drop across the

upper MOSFET for over-current protection.

www.richtek.com

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DS9202-02 August 2002

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