SG5851A Datasheet, PDF (1/12 Pages) Fairchild Semiconductor – Low-Cost, Green-Mode, PWM Controller for Flyback Converters

August 2008
SG5851A
Low-Cost, Green-Mode, PWM Controller for Flyback
Converters
Features
ƒ Green-Mode PWM
ƒ Supports the “Blue Angel” Standard
ƒ Low Startup Current: 9µA
ƒ Low Operating Current: 3mA
ƒ Leading-Edge Blanking
ƒ Constant Output Power Limit
ƒ Universal Input
ƒ Built-in Synchronized Slope Compensation
ƒ Current Mode Operation
ƒ Cycle-by-cycle Current Limiting
ƒ Under-Voltage Lockout (UVLO)
ƒ Programmable PWM Frequency with Frequency
Hopping
ƒ VDD Over-Voltage Protection (Auto Restart)
ƒ Gate Output Voltage Clamped at 17V
ƒ Low Cost
ƒ Few External Components Required
Applications
ƒ Power Adaptors
ƒ Open-Frame SMPS
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
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
AC input range (90VAC to 264VAC). 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 output driver is
clamped at 17V. SG5851A controllers, available in an
SOP package, can be used to improve the performance
and reduce the production cost of power supplies.
Ordering Information
Part Number
SG5851ASY
SG5851ADY
Operating
Temperature Range
Package
-40°C to +105°C 8-pin Small Outline Package (SOP)
-40°C to +105°C 8-pin Dual in-line Package (DIP)
Eco Status
Green
Green
Packing
Method
Tape & Reel
Tube
For Fairchild’s definition of “green” Eco Status, please visit: http://www.fairchildsemi.com/company/green/rohs_green.html.
© 2008 Fairchild Semiconductor Corporation
SG5851A • Rev. 1.0.0
www.fairchildsemi.com