SC4812 Просмотр технического описания (PDF) - Semtech Corporation

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SC4812

Current Mode PWM Controller with Integrated Start-up Circuit and Op Amp

Semtech Corporation 

SC4812

Current Mode PWM Controller with

Integrated Start-up Circuit and Op Amp

POWER MANAGEMENT

Description

The SC4812 is a highly integrated current mode PWM

controller designed for isolated or non-isolated dc-dc con-

verters in telecommunication and data communication

applications. It minimizes the amount of external discrete

components needed and leads to substantial cost and

space saving converter designs.

The circuitry of the SC4812 includes an integrated high

voltage start-up circuit suitable for telecom/industrial

voltage applications. It is disabled during regular opera-

tion and improves efficiency. Current mode control with

leading-edge blanking simplifies control loop design and

internal ramp compensation circuit stabilizes the current

loop when operating above 50% duty cycle. Internal er-

ror amplifier could be used for non-isolated applications.

Features

‹ Wide input range 12V to 90V

‹ High-voltage start-up circuit

‹ Current mode control

‹ Transconductance error amplifier

‹ Leading-edge blanking

‹ Cycle by cycle current limit

‹ Programmable external soft-start

‹ Thermal shutdown

‹ SO-8 package. Fully WEEE and RoHS compliant

Applications

‹ IP phones, PoE

‹ Telecom isolated converters

‹ Off-line isolated power supplies

‹ Instrumentation power supplies

‹ Battery chargers

Typical Application Circuit

Vin

C2

R2

T1

R1

C3

C4

U1

D1

Vout

C1

Q1

2 FB

OUT 7

SC4812

3 COMP

CS 5

C5

R3

4 SS/SHDN GND 6

R4

R5

C6

Revision: February 6, 2007

1

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