SG6858 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
SG6858
FEATURES
„ Green-mode PWM
„ Supports the “Blue Angel” standard
„ Low start-up current (10µA)
„ Low operating current (2.5mA)
„ 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
„ 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
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 meet
even the strictest power conservation requirements.
The BiCMOS fabrication process enables reducing the
start-up current to 10µA and the operating current to
2.5mA. 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 events, the SG6858’s
output driver is clamped at 17V. SG6858 controllers can
be used to improve the performance and reduce the
production cost of power supplies and can replace 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 (IAO33.0045.B2)
-1-
www.sg.com.tw • www.fairchildsemi.com
September 25, 2007