APW7062BKC-TRG Ver la hoja de datos (PDF) - Anpec Electronics

Número de pieza

componentes Descripción

Fabricante

APW7062BKC-TRG

Synchronous Buck PWM Controller

Anpec Electronics 

APW7062B

Function Pin Description

RT (Pin1)

This pin can adjust the switching frequency. Connect a

resistor from the RT to the GND for increasing the switch-

ing frequency:

FS = 200kHz + 4.15 ×106

RT

(RT to GND,FS = 200kHz to 400kHz)

Conversely, connect a resistor from the RT to the VCC for

decreasing the switching frequency:

FS = 200kHz - 3.51 × 10 7

RT

(RT to VCC,FS = 200kHz to 75kHz)

output is rising rapidly. Until the output is in regulation at

t2, the clamp on the COMP is released. This method pro-

vides a rapid and controlled output voltage rise.

When over-current protection occurs, the VOUT is

shutdown, and re-soft-start again, if the over current con-

dition still exists in soft-start, the VOUT is shutdowned

again. After the SS reaches 4.5V, the SS is discharged to

zero. The soft-start is recurring until the over current con-

dition is eliminated.

VOLTAGE

VSOFT-START

OCSET (Pin2)

This pin serves two functions: a shutdown control and

the setting of over current-limit threshold. Pulling this pin

below 1.27V will shutdown the controller, forcing the

UGATE and LGATE signals to be at 0V.

A resistor (Rocset) connected between this pin and the drain

of the high side MOSFET will determine the over current

limit. An internal 200µA current source will flow through

this resistor, creating a voltage drop, which will be com-

pared with the voltage across the high side MOSFET.

The threshold of the over current limit is therefore given

by:

( ) IOCSET 200uA R × OCSET

IPEAK =

RDS(ON)

To avoid the noise interference from switching transient,

a delay time is designed in the OCP comparator.

The over-current protection is active only when the high

side MOSFET is turned on longer than 300ns.

SS (Pin3)

Connect a capacitor from the pin to the GND to set the

soft-start interval of the converter. An internal 10µA current

source charges this capacitor to 5.8V. The SS voltage

clamps the error amplifier output, and Figure1 shows the

soft-start interval. At t1, the SS voltage reaches the valley

of the oscillator’s triangle wave. The PWM comparator

starts to generate a PWM signal to control logic, and the

VOSC(MIN)

VSS=1.2V

VOUT

Error Amp

Output

t0

t1

t2

t3

Figure 1. Soft-Start Interval

TIME

I t2 = CSS ×(VOSC(MIN)+ t1)

SS

= − = × × tSoftStart t3 t2

CSS

V

OUT SteadyState ∆VOSC

ISS

VIN

Where :

t1=1.2V

CSS = Soft-Start Capacitor

ISS = Soft-Start Current = 10µA

V

= Bottom of Oscillator = 1.35V

OSC(MIN)

V = Input Voltage

IN

∆Vosc = Peak to Peak Oscillator Voltage = 1.9V

∆VOUTSteadyState = Steady State Output Voltage

Copyright © ANPEC Electronics Corp.

9

Rev. A.4 - Oct., 2008

www.anpec.com.tw

Share Link: