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RT9214GS

5V/12V Synchronous Buck PWM DC-DC Controller

Richtek Technology 

RT9214

Typical Application Circuit

+5V to +12V D1

1N4148

RBOOT

2.2

R1

10

C1

1uF

1 BOOT UGATE 2

5 VCC

PHASE 8

6

FB

RT9214

OPS

7

3 GND

LGATE 4

C2

0.1uF

RUGATE

2.2

ROCSET

Disable >

Q3

3904

R2

R3

32

68

R4

C5

200-1k 0.1-0.33uF

VIN

+3.3V/+5V/+12V

C3

C4

1uF

470uF

Q1

MU

L1

3uH

VOUT

Q2 R

ML

C

C6 to C8

1000uFx3

VOUT

=

VREF

× (1+

R3 )

R2

VREF : Internal reference voltage

(0.8V ± 2%)

Functional Pin Description

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.

UGATE (Pin 2)

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

side power N-Channel MOSFET. This pin is monitored by

the adaptive shoot-through protection circuitry to

determine when the upper MOSFET has turned off.

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.

LGATE (Pin 4)

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

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

adaptive shoot-through protection circuitry to determine

when the lower MOSFET has turned off.

FB (Pin 6)

Switcher feedback voltage. This pin is the inverting input

of the error amplifier. FB senses the switcher output

through an external resistor divider network.

OPS (OCSET, POR and Shut-Down) (Pin 7)

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.

PHASE (Pin 8)

Connect this pin to the source of the upper MOSFET and

the drain of the lower MOSFET.

NC [Exposed Pad (9)]

No Internal Connection.

VCC (Pin 5)

Connect this pin to a well-decoupled 5V or 12V bias

supply. It is also the positive supply for the lower gate

driver, LGATE.

www.richtek.com

2

DS9214-13 September 2007

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