RT9228CS datasheet(4/10 Pages) RICHTEK

4 / 10 page

RT9228

www.richtek.com

DS9228-03 July 2001

Function Block Diagram

Functional Pin Description

VCC (Pin 1)

Provide a 12V bias supply for the IC to this pin. This

pin also provides the gate bias charge for all the

MOSFETs controlled by the IC.

VID0, VID1, VID2, VID3, VID4 (Pin 6, 5, 4, 3, and 2)

VID0~4 are the input pins to the 5-bit DAC. The

states of these five pins program the internal voltage

reference, DACOUT. The level of DACOUT sets the

core converter output voltage. It also sets the core

PGOOD and OVP thresholds. Table 1 specifies the

DACOUT voltage of 32 combinations of VID levels.

PGOOD (Pin 7)

PGOOD is an open collector output used to indicate

the status of the output voltage. This pin is pulled low

when the core output is not within

±10% of the

DACOUT reference voltage and the other outputs are

below their under-voltage thresholds.

The PGOOD output is open for ‘11111’ VID codes

that inhibit operation. See table 1.

FAULT (Pin 8)

This pin is low during normal operation, but it is

pulled to about 8V (VCC = 12V) in the event of an

over-voltage or over-current condition.

SS (Pin 9)

Connect a capacitor from this pin to ground. This

capacitor, along with an internal 11

µA (VSS>1V)

current source, sets the soft-start interval of the

converter.

110%

90%

115%

POWER-ON

RESET (POR)

SOFT-START

& FAULT

LOGIC

TTL D/A

CONVERTER

(DAC)

OSCILLATOR

GATE

CONTROL

LOGIC

LINEAR

UNDER

VOLTAGE

PGOOD

PHASE1

LGATE1

PGND

GND

VCC

FB3

FAULT

VID0

VID1

VID2

VID3

3.3V

OCSET1

VSEN1

COMPENSATION

GATE3

0.3V

3.3V

VIN2

1.26V

VOUT2

FB2

0.25A

VCC

µA

VID4

DACOUT

ERROR

AMP

LUV

OC1

FB1

PWM

INHIBIT

PWM COMP

LOWER

DRIVE

VCC

UPPER

DRIVE

UGATE1

200

µA

OC2

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