RT9218BGS datasheet(3/17 Pages) RICHTEK

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RT9218B

DS9218B-09 March 2007

www.richtek.com

Functional Pin Description

UGATE (Pin 2)

Upper gate driver output. Connect to gate of the high-side

power N-MOSFET. This pin is monitored by the adaptive

shoot-through protection circuitry to determine when the

upper MOSFET has turned off.

BOOT (Pin 1)

Bootstrap supply pin for the upper gate driver. Connect

the bootstrap capacitor between BOOT pin and the PHASE

pin. The bootstrap capacitor provides the charge to turn

on the upper MOSFET.

PHASE (Pin 14)

Connect this pin to the source of the upper MOSFET and

the drain of the lower MOSFET.

OPS (OCSET, POR and Shut-Down) (Pin 13)

This pin provides multi-function of the over-current setting,

UGATE turn-on POR sensing, and shut-down features.

Connecting a resistor (ROCSET) between OPS and PHASE

pins sets the over-current trip point.

Pulling the pin to ground resets the device and all external

MOSFETs are turned off allowing the output voltage power

rails to float.

This pin is also used to detect VIN in power on stage and

issues an internal POR signal.

LGATE (Pin 4)

Lower gate drive output. Connect to gate of the low-side

power N-MOSFET. This pin is monitored by the adaptive

shoot-through protection circuitry to determine when the

lower MOSFET has turned off.

FB (Pin 12)

Switcher feedback voltage. This pin is the inverting input

of the error amplifier. FB senses the switcher output through

an external resistor divider network.

VCC (Pin 11)

Connect this pin to a well-decoupled 12V bias supply. It

is also the positive supply for the lower gate driver, LGATE.

GND (Pin 3)

Both signal and power ground for the IC. All voltage levels

are measured with respect to this pin. Ties the pin directly

to the low-side MOSFET source and ground plane with

the lowest impedance.

DRV (Pin 5)

Connect this pin to the base/gate of an external transistor/

MOSFET. This pin provides the drive for the linear

regulator's pass transistor/MOSFET.

FBL (Pin 9)

Linear regulator feedback voltage. This pin is the inverting

input of the error amplifier and protection monitor. Connect

this pin to the external resistor divider network of the linear

regulator.

PGOOD (Pin 10)

PGOOD is an open-drain output used to indicate that the

regulator is within normal operating voltage ranges and

it's implemented with a specific sequence as following

chart.

NC (Pin 6,7,8)

No internal connection.

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