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SC4812

Current Mode PWM Controller with

Integrated Start-up Circuit and Op Amp

POWER MANAGEMENT

Revision: February 6, 2007

Description

Features

Applications

Typical Application Circuit

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

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.

IP phones, PoE

Telecom isolated converters

Off-line isolated power supplies

Instrumentation power supplies

Battery chargers

C6

C4

R1

R4

C3

C2

C5

R3

Q1

C1

R5

SS/SHDN

4

FB

2

COMP

3

CS

5

GND

6

OUT

7

U1

SC4812

D1

R2

Vin

T1

Vout