|
FAN4800A Datasheet, PDF (1/24 Pages) Fairchild Semiconductor – PFC/PWM Controller Combination | |||
|
March 2009
FAN4800A/C, FAN4801/1S/2/2L
PFC/PWM Controller Combination
Features
 Pin-to-Pin Compatible with ML4800 and FAN4800
and CM6800 and CM6800A
 PWM Configurable for Current-mode or
Feed-forward Voltage-Mode Operation
 Internally Synchronized Leading-Edge PFC and
Trailing-Edge PWM in one IC
 Low Operating Current
 Innovative Switching-Charge Multiplier Divider
 Average-Current-Mode for Input-Current Shaping
 PFC Over-Voltage and Under-Voltage Protections
 PFC Feedback Open-Loop Protection
 Cycle-by-Cycle Current Limiting for PFC/PWM
 Power-on Sequence Control and Soft-Start
 Brownout Protection
 Interleaved PFC/PWM Switching
 FAN4801/1S/2/2L Improve Efficiency at Light Load
 fRTCT=4â¢fPFC=4â¢fPWM for FAN4800A and
FAN4801/1S
 fRTCT=4â¢fPFC=2â¢fPWM for FAN4800C and
FAN4802/2L
Applications
 Desktop PC Power Supply
 Internet Server Power Supply
 LCD TV, Monitor Power Supply
 UPS
 Battery Charger
 DC Motor Power Supply
 Monitor Power Supply
 Telecom System Power Supply
 Distributed Power
Description
The highly integrated FAN4800A/C and
FAN4801/1S/2/2L are specially designed for power
supplies that consist of boost PFC and PWM. They
require very few external components to achieve
versatile protections / compensation. They are available
in 16-pin DIP and SOP packages.
The PWM can be used in either current or voltage
mode. In voltage mode, feed-forward from the PFC
output bus can reduce the secondary output ripple.
Compared with older productions, ML4800 and
FAN4800, FAN4800A/C and FAN4801/1S/2/2L have
lower operation current that save power consumption in
external devices. FAN4800A/C and FAN4801/1S/2/2L
have accurate 49.9% maximum duty of PWM that
makes the hold-up time longer. Specifically, the
brownout protection and PFC soft-start functions are not
in ML4800 and FAN4800.
To start evaluating FAN4800A/C, FAN4801/1S/2/2L for
replacing existing FAN4800 and ML4800 boards, five
things must be done before the fine-tuning procedure:
1. Change RAC resister from the old value to a higher
resister: between 6MΩ to 8MΩ.
2. Change RT/CT pin from the existing values to
RT=6.8KΩ and CT=1000pF to have fPFC=64KHz,
fPWM=64KHz.
3. VRMS pin needs to be 1.224V at VIN=85 VAC for
universal input application from line input from
85VAC to 270 VAC. Both poles for the Vrms of
FAN4801/1S/2/2L donât need to substantially
slower than FAN4800; about 5 to 10 times.
4. At full load, the average VEA needs to ~4.5V and
the ripple on the VEA needs to be less than 400mV.
5. Soft-Start pin, the soft-start current has been
reduced to half from the FAN4800 capacitor.
Related Resources
Complete design instructions are detailed in application
note AN-6078SC (available in Chinese only).
© 2008 Fairchild Semiconductor Corporation
FAN4800A/C, FAN4801/1S/2/2L ⢠Rev. 1.0.1
www.fairchildsemi.com
|
▷ |