Product Specification

Highly Integrated Green-Mode PWM Controller

SG6742

© System General Corp.

- 1 -

www.sg.com.tw • www.fairchildsemi.com

Version 1.0.1 (IAO33.0083.B0)

September 24, 2007

FEATURES

High-voltage start-up

Low operating current (4mA)

Linearly decreasing PWM frequency to 22KHz

Frequency jittering to reduce EMI emission

Fixed PWM frequency (65KHz)

Peak-current-mode control

Cycle-by-cycle current limiting

Leading-edge blanking

Synchronized slope compensation

Internal open-loop protection

GATE output maximum voltage clamp (18V)

Programmable over-temperature protection (RT)

Internal latch circuit (OVP, RT)

Constant power limit (full AC input range)

Internal OTP sensor with hysteresis

APPLICATIONS

General-purpose switch-mode power supplies and

flyback power converters, including:

Power Adapters

Open-Frame SMPS

DESCRIPTION

The highly integrated SG6742 series of PWM controllers

provides several features to enhance the performance of

flyback converters.

To minimize standby power consumption, a proprietary

green-mode function provides off-time modulation to

linearly decrease the switching frequency at light-load

conditions. To avoid acoustic noise problems, the

minimum PWM frequency is set above 22KHz. This

green-mode function enables the power supply to meet

international power conservation requirements. With the

internal high-voltage start-up circuitry, the power loss due

to bleeding resistors is eliminated. To further reduce power

consumption, SG6742 is manufactured using the BiCMOS

process, which allows an operating current of 4mA.

SG6742 integrates a frequency a hopping function that

helps reduce EMI emission of a power supply with

minimum line filters. Also, its built-in synchronized slope

compensation achieves stable peak-current-mode control.

The proprietary internal line compensation ensures

constant output power limit over a wide AC input voltages,

SG6742 provides many protection functions. In addition

to cycle-by-cycle current limiting, the internal open-loop

protection circuit ensures safety should an open-loop or

output short-circuit failure occur. PWM output is disabled

26V, the internal OVP circuit is triggered.

SG6742 is available in an 8-pin DIP or SOP package.

TYPICAL APPLICATION