SG6859 Datasheet, PDF (1/13 Pages) Fairchild Semiconductor – Low Cost Green-Mode PWM Controller for Flyback Converters

Low Cost Green-Mode PWM Controller for Flyback Converters
Product Specification
SG6859
FEATURES
„ Green-Mode PWM
„ Supports the “Blue Angel” Standard
„ Low Start-up Current (9uA)
„ Low Operating Current (3mA)
„ 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
„ V_DD Over Voltage Protection (Auto Restart)
„ Gate Output Voltage Clamped at 17V
„ Low Cost
„ Few External Components Required
„ Small SOT-26 and Dip 8 Packages
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 other
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 special 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 easily meet even the strictest power
conservation requirements.
The BiCMOS fabrication process enables reducing
the start-up current to 9uA, and the operating current to
3mA. To further improve power conservation, a large
start-up 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 (90V_AC to 264V_AC). Pulse-by-pulse current limiting
ensures safe operation even during short-circuits.
To protect the external power MOSFET from being
damaged by supply over voltage, the SG6859’s output
driver is clamped at 17V. SG6859 controllers can be used
to improve the performance and reduce the production
cost of power supplies. The SG6859 is the best choice for
replacing linear and RCC-mode power adapters. It is
available in 8-pin DIP and 6-pin SOT-26 packages.
TYPICAL APPLICATION
© System General Corp.
Version 1.2.1(IAO33.0067.B2)
SG6859
-1-
www.sg.com.tw • www.fairchildsemi.com
September 28,2007