RT9232BGS Ver la hoja de datos (PDF) - Richtek Technology

Número de pieza

componentes Descripción

Fabricante

RT9232BGS

Programmable Frequency Synchronous Buck PWM Controller

Richtek Technology 

Function Block Diagram

VCC EN

Power-On

-

Reset (POR)

+

10uA

POR

SS

Soft Start

and

0.6V

+

UV

Fault Logic

-

INHIBIT

FB

COMP

+

- EA

0.8V +

Reference

+

+

PWM

-

Oscillator

Driver Logic

RT9232B

OCSET

200uA

BOOT

UGATE

PHASE

PVCC

LGATE

PGND

GND

RT

Operation

Startup

RT9232B initializes automatically after receiving both VCC

and VIN power. Special power-on sequence is not

necessary. The Power-On Reset (POR) function

continually monitors input supply voltages and enable

voltage. POR function monitors IC power via VCC pin and

external MOSFET power via OCSET pin. Voltage on

OCSET pin is a fixed voltage drop less than VIN. When

voltages on VCC, OCSET, and EN pins exceed their

thresholds, POR function initializes soft-start operation.

POR inhibits driver operation while EN pin pulls low.

Transitioning EN pin high after input supply voltages ready

initializes soft-start operation.

Soft-Start

After POR function releases soft-start operation, an internal

10uA current source charges an external capacitor on SS

pin (Css) to 5V. Soft-start function clamps both COMP &

FB pins to SS pin voltage & a fixed voltage drop less than

SS pin voltage respectively. Thus upper MOSFET turns

on at a limited duty and output current overshoot can be

reduced. This method provides a rapid and controlled

output voltage rise.

OCP

The OCP function monitors output current by using upper

MOSFET RDS(ON). The OCP function cycles soft-start

function in a hiccup mode. Overcurrent triggering level

can be arbitrarily set by adjusting ROCSET. An Internal 200μA

current sink makes a voltage drop across ROCSET from

VIN. When VPHASE is lower than VOCSET, OCP function

initializes soft-start cycles. The soft-start function

discharges CSS with 10μA current sink and disable PWM

function. Then soft-start function recharges Css and PWM

operation resumes. The soft-start hiccup restarts after

SS voltage fully charges to 4V if the output short event

still remains. The converter is shutdown permanently after

3 times hiccup and only restarting supply voltages can

enable the converter. The OCP funcion will be triggered

as inductor current reach :

IL(MAX)

=

IOCSET × ROCSET

RDS(ON)

DS9232B-03 March 2007

www.richtek.com

3

Share Link: