March 2010

© 2007 Fairchild Semiconductor Corporation

www.fairchildsemi.com

SG6859A • Rev. 1.0.3

SG6859A

Low-Cost, Green-Mode PWM Controller for Flyback Converters

Features

Green-Mode PWM

Supports the “Blue Angel” Standard

Low Startup Current: 9μA

Low Operating Current: 3mA

300mA Driving Capability

Leading-Edge Blanking

Constant Output Power Limit

Universal Input

Built-in Synchronized Slope Compensation

Current-Mode Operation

Cycle-by-cycle Current Limiting

Under-Voltage Lockout (UVLO)

Programmable PWM Frequency with Frequency

Hopping

Gate Output Voltage Clamped at 17V

Low Cost

Few External Components Required

Small SSOT-6 Package

Applications

General-purpose switching mode power supplies and

flyback power converters, such as:

Battery chargers for cellular phones, cordless

phones, PDAs, digital cameras, and power tools

Power adapters for ink jet printers, video game

consoles, and portable audio players

Open-frame SMPS for TV/DVD standby and auxiliary

supplies, home appliances, and consumer electronics

Replacements for linear transformers and RCC SMPS

PC 5V standby power

Description

This highly integrated PWM controller provides several

enhancements designed to meet the low standby-power

needs of low-power SMPS. To minimize standby power

consumption, the proprietary green-mode function

provides off-time modulation to linearly decrease the

switching frequency under light-load conditions. This

green-mode function enables the power supply to meet

even the strictest power conservation requirements.

The BiCMOS fabrication process enables reducing the

startup current to 9μA and the operating current to 3mA.

To further improve power conservation, a large startup

resistance can be used. Built-in synchronized slope

compensation ensures the stability of peak current

mode

control.

Proprietary

internal

compensation

provides a constant output power limit over a universal

limiting ensures safe operation during short-circuits.

To protect the external power MOSFET from damage by

supply over voltage, the SG6859A’s output driver is

clamped at 17V. SG6859A controllers can be used to

improve the performance and reduce the production

cost of power supplies. The best choice for replacing

linear and RCC-mode power adapters, the SG6859A is

available in 8-pin DIP and 6-pin SSOT-6 packages.