September 2008
FAN400A — Low-Power Green-Mode PWM Flyback Power
Controller without Secondary Feedback
Features
Description
This highly integrated PWM controller provides several
features to enhance the performance of low-power
flyback converters. To minimize standby power
Linearly Decreasing PWM Frequency
Green Mode Under Light-Load and Zero-Load
Conditions
consumption,
a
proprietary green-mode function
provides off-time modulation to linearly decrease the
switching frequency under light-load and zero-load
conditions. This green mode enables the power supply
to meet international power conservation requirements.
The supply voltage VDD is also used for feedback
compensation, to regulate the output voltage without
requiring a conventional TL431 and a photo-coupler.
Another advantage of the FAN400A is that the typical
startup current is only 8μA, while the typical operating
current can be as low as 3.6mA. A large startup
resistance can be used to achieve even higher power
conversion efficiency.
Constant Voltage (CV) and Constant Current (CC)
No Secondary Feedback
Low Startup Current: 8μA
Low Operating Current: 3.6mA
Leading-Edge Blanking
Constant Power Limit
Universal AC Input Range
Synchronized Slope Compensation
140°C OTP Sensor with Hysteresis
VDD Over-Voltage Clamping
Cycle-by-Cycle Current Limiting
Under-Voltage Lockout (UVLO)
Fixed PWM Frequency with Hopping
Gate Output Maximum Voltage Clamped at 17V
Small SSOT-6 Package
FAN400A integrates a frequency hopping function
internally to reduce EMI emissions with minimum line
filters. 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 FAN400A provides many protection functions.
Pulse-by-pulse current limiting ensures constant output
current, even if a short circuit occurs. The internal
protection circuit disables PWM output if VDD exceeds
22.7V. The gate output is clamped at 17V to protect the
power MOS from over-voltage damage. The built-in
over-temperature protection (OTP) function shuts down
the controller at 140°C with a 30°C hysteresis.
Applications
General-purpose, switching mode, power supplies and
flyback power converters, such as:
Battery Chargers for Cellular Phones, Cordless
Phones, PDAs, Digital Cameras, Power Tools
The FAN400A is designed to provide a low-cost total
solution for flyback converters. It is available in a small-
footprint, 6-pin, SSOT-6 package.
Power Adapters for Ink Jet Printers, Video Game
Consoles, Portable Audio Players
Open-Frame SMPS for TV/DVD Standby and
Auxiliary Supplies, Home Appliances, Consumer
Electronics
Related Resources
Replacement for Linear Transformers and RCC SMPS
PC 5V Standby Power
AN-400A Low-Power Green-Mode PWM Flyback
Power Controller without Secondary Feedback
Ordering Information
Part Number Operating Temperature Range
Package
Packing Method
Eco Status
Green
FAN400ATY
FAN400ANY
SSOT-6
DIP-8
Tape & Reel
Tube
-40°C to +105°C
-40°C to +105°C
Green
For Fairchild’s definition of “green” please visit: http://www.fairchildsemi.com/company/green/rohs_green.html.
© 2008 Fairchild Semiconductor Corporation
FAN400A Rev. 1.0.1
www.fairchildsemi.com