SG6841SZ3 Datasheet, PDF (1/14 Pages) Fairchild Semiconductor – High-integrated Green-mode PWM Controller

High-integrated Green-mode PWM Controller
Product Specification
SG6841
FEATURES
„ Green-mode PWM to support “Blue Angel” Norm
„ Low start up current 30uA
„ Low operation current 3mA
„ Leading-edge blanking
„ Built-in synchronized slope compensation
„ Constant output power limit for universal AC input
„ Current mode operation
„ Cycle-by-cycle current limiting
„ Under voltage lockout (UVLO)
„ Programmable PWM frequency
„ GATE output maximum voltage clamped at 18V
„ Totem pole output includes soft driving for better
EMI
„ Build-in limited-power-control to meet safety
requirement
„ Programmable over-temperature protection
„ Few external components & low cost solution
DESCRIPTION
This highly integrated PWM controllers, SG6841 series,
provides several features to enhance the performance of
low power flyback converters. 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 assists the power
supply to easily meet the power conservation
requirement. Due to BiCMOS process, the start-up
current and operation current is reduced to 30uA and
3mA, respectively, to improve power conversion
efficiency. Large start-up resistance can be used for
further power saving. Built-in synchronized slope
compensation ensures the stability of peak current mode
control. A proprietary internal compensation ensures
constant output power limit for universal AC input
voltage from 90VAC to 264VAC.
APPLICATIONS
General-purpose switching mode power supplies
and flyback power converters, and
„ Power Adapter
„ Open-frame SMPS
„ Battery Charger Adapter
SG6841 provides many protection functions.
Pulse by pulse current limit ensures a constant output
current under short circuit. If a short circuit failure or
over load happens, the SG6841 will shut off after a
continuous high voltage detection on FB pin. The gate
output is clamped at 18V to protect the power MOS
from over voltage damage. An external NTC
thermistor can be applied to sense the ambient
temperature for over-temperature protection. The
SG6841 series are available in 8-pin DIP and SO
packages.
TYPICAL APPLICATION
From bridge rectifier
127~ 373VDC
RIN
D1 From auxiliary
winding
C _IN
RA
RT
RI
VIN
RT
VDD
GATE
RI ^SG6842
SENSE
FB
GND
Rg
Q1
R_S
©System General Corp.
-1-
Version 2.1 (IRO33.0001.B5)
www.sg.com.tw
Jun.15,2006