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FAN4800AS Datasheet, PDF (1/19 Pages) Fairchild Semiconductor – PFC/PWM Controller Combination | |||
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December 2010
FAN4800AS/CS/01S/2S
PFC/PWM Controller Combination
Features
 Pin-to-Pin Compatible with ML4800 and FAN4800
and CM6800 and CM6800A
 PWM Configurable for Current Mode or
Feedforward 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
 Improved Efficiency at Light Load
 fRTCT=4â¢fPFC=4â¢fPWM for FAN4800AS/01S
 fRTCT=4â¢fPFC=2â¢fPWM for FAN4800CS/02S
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
Related Resources
 AN-8027 - FAN480X PFC+PWM Combination
Controller Application
Description
The highly integrated FAN4800AS/CS/01S/02S parts
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, FAN4800AS/CS/01S/02S have lower
operation current that saves power consumption in
external devices. FAN4800AS/CS/01S/02S have
accurate 49.9% maximum duty of PWM that makes the
hold-up time longer. Brownout protection and PFC soft-
start functions available in this series are not available
in ML4800 and FAN4800.
To evaluate FAN4800AS/CS/01S/02S for replacing
existing FAN4800 and ML4800 boards, five things must
be completed 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 and
fPWM=64kHz.
3. The VRMS pin needs to be 1.224V at VIN=85 VAC
for universal input application from line input from
85VAC to 270VAC.
4. At full load, the average VVEA needs to be ~4.5V
and the ripple of VVEA needs to be less than
400mV.
5. For the Soft-Start pin, the soft-start current has
been reduced to half the FAN4800 capacitor.
There are two differences from FAN4800A/C/01/02 to
FAN4800AS/CS/01S/02S:
1. Under-voltage protection debounce time is
extended to one second.
2. PWM gate clamp voltage is raised to 19V.
© 2010 Fairchild Semiconductor Corporation
FAN4800AS/CS/01S/02S ⢠Rev. 1.0.1
www.fairchildsemi.com
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