SG6849 Datasheet, PDF (1/15 Pages) List of Unclassifed Manufacturers – Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback

Product Specification
Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback
SG6849
FEATURES
Linearly Decreasing PWM Frequency
Green-Mode under Light-Load and Zero-Load
Conditions
Constant Voltage (CV) and Constant Current (CC)
No Secondary Feedback
Low Startup Current (5uA)
Low Operating Current (3.6mA)
Leading-Edge Blanking
Constant Power Limit
Universal AC Input Range
Synchronized Slope Compensation
150°C OTP Sensor with Hysteresis
V_DD Over Voltage Clamping
Cycle-by-Cycle Current Limiting
Under Voltage Lockout (UVLO)
Fixed PWM Frequency (65kHz/100kHz)
Gate Output Maximum Voltage Clamped at 16.7V
Small SOT-26 Package
APPLICATIONS
Low-power 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, consumer
electronics, and PC 5V standby-power.
Replacements for linear transformers and RCC
SMPS.
DESCRIPTION
This highly integrated PWM controller 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 and zero-load conditions. This
green-mode function enables the power supply to easily
meet international power conservation requirements. The
supply voltage V_DD is also used for feedback
compensation, to regulate the output voltage without
requiring a conventional TL431 and a photo-coupler.
Another advantage of the SG6849 is that the typical
startup current is only 5uA, while the typical operating
current can be as low as 3.6mA. A large startup resistance
could be used to achieve even higher power conversion
efficiency. Built-in synchronized slope compensation
maintains the stability of peak current-mode control.
Proprietary internal compensation ensures constant output
power limiting over a universal range of AC input
voltages, from 90VAC to 264VAC.The SG6849 provides
many protection functions. Pulse-by-pulse current
limiting ensures a constant output current, even if a short
circuit occurs. Also, the internal protection circuit will
disable PWM output, if V_DD exceeds 22.7V. The gate
output is clamped at 16.7V to protect the power MOS
from over-voltage damage. The built-in over temperature
protection (OTP) function will shutdown the controller at
150°C with a 20°C hysteresis. The SG6849 is designed to
provide a low-cost total solution for flyback converters. It
is available in a small footprint, 6-pin, SOT-26 package.
TYPICAL IC APPLICATION
V IN
R IN
C IN
D1
VDD
Q1
G ATE
W AUX
SENSE
GND
RS
DO
CO
VO
© System General Corp.
-1-
Version 1.0(IRO33.0002.B3)
www.sg.com.tw
Dec.29, 2003