SG6859A - Low-Cost, Green-Mode PWM Controller for Flyback Converters

Oct 12, 2026

SG6859A is a highly integrated low-cost, green-mode PWM controller intended for flyback converters and general-purpose low-power switching supplies. It reduces standby power via off-time modulation that lowers switching frequency under light load, supports constant output power limiting across a universal 90–264VAC input range, and includes synchronized slope compensation for stable peak current-mode control. Built-in pulse-by-pulse current limiting, UVLO, and VDD over-voltage auto-restart protection help safeguard the power MOSFET. Designed for small SSOT-6 or DIP-8 packages with minimal external components.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages13

Reading Time33 min

AccessFree to download

Features

Applications

Description

Ordering Information

Part Numbers and Packages

Application Diagram

Typical Application

Internal Block Diagram

Functional Block Diagram

Marking Information

Pin Configurations

SSOT-6 Pin Configuration

DIP-8 Pin Configuration

Absolute Maximum Ratings

SG6859A Low Cost, Green Mode PW M Controller for Flyback Converters © 2007 Fairchild Semiconductor Corporation [www.fairchildsemi.com](www.fairchildsemi.com) [SG6859A](SG6859A) • Rev. 1.0.3 | |
March 2010 | | --- | --- | | 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
􀂃 VDD Over-Voltage Protection (Auto Restart)
􀂃 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 9 μA 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 AC input range (90VAC to 264VAC) . Pulse-by-pulse current 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. | — - Ordering Information | Part Number | Operating Temperature Range | Package | Eco Status
| Packing Method | | --- | --- | --- | --- | --- | | SG6859ATZ | -40 to +105°C | SSOT-6 | RoHS | Tape & Reel | | SG6859ATY | -40 to +105°C | SSOT-6 | Green | Tape & Reel | | SG6859ADZ | -40 to +105°C | DIP-8 | RoHS | Tube | | SG6859ADY | -40 to +105°C | DIP-8 | Green | Tube | For Fairchild’s definition of Eco Status, please visit: [http://www.fairchildsemi.com/company/green/rohs_green.htm](http://www.fairchildsemi.com/company/green/rohs_green.html)[l](http://www.fairchildsemi.com/company/green/rohs_green.html) Application Diagram Figure 1. Typical Application Internal Block Diagram Figure 2. Functional Block Diagram SG6859A—Low-Cost, Green-Mode PW M Controller for Flyback Converters © 2007 Fairchild Semiconductor Corporation [www.fairchildsemi.com](www.fairchildsemi.com) [SG6859A](SG6859A) • Rev. 1.0.3 2 | Marking Information | | | | --- | --- | --- | | | AAJF: SG6859A
W: Week Code A~Z=W1~W26
A~Z=W27~W52
: Lead Free Package | | | *Marking for SG6859ATZ (Pb-free) | | | | | XXXX: AAJF=SG6859AT : Die Run Code
: Year Code
- - - : Week Code | | | *Marking for SG6859ATY (Green Compound) | | | | | | T: D=DIP
P: Z= Lead Free + RoHS Compatible Null=Regular P

FAQs

What key design goal does the SG6859A target?

It targets low standby-power needs in low-power SMPS by using a proprietary green-mode function that modulates off-time to reduce switching frequency under light-load conditions.

How does SG6859A help maintain stable current-mode control?

It uses built-in synchronized slope compensation, which ensures stability of peak current mode control.

What protections are included to safeguard operation and the external MOSFET?

SG6859A includes cycle-by-cycle current limiting, under-voltage lockout (UVLO), pulse-by-pulse current limiting for short-circuit safety, and output driver clamping at 17V to protect the external power MOSFET from supply over-voltage damage.

Oct 12, 2026

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