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FAN4802L View Datasheet(PDF) - Fairchild Semiconductor

Part Name
Description
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FAN4802L
Fairchild
Fairchild Semiconductor Fairchild
FAN4802L Datasheet PDF : 24 Pages
1 2 3 4 5 6 7 8 9 10 Next Last
March 2009
FAN4800A/C, FAN4801/1S/2/2L
PFC/PWM Controller Combination
Features
ƒ Pin-to-Pin Compatible with ML4800 and FAN4800
and CM6800 and CM6800A
ƒ PWM Configurable for Current-mode or
Feed-forward Voltage-Mode Operation
ƒ Internally Synchronized Leading-Edge PFC and
Trailing-Edge PWM in one IC
ƒ Low Operating Current
ƒ Innovative Switching-Charge Multiplier Divider
ƒ Average-Current-Mode for Input-Current Shaping
ƒ PFC Over-Voltage and Under-Voltage Protections
ƒ PFC Feedback Open-Loop Protection
ƒ Cycle-by-Cycle Current Limiting for PFC/PWM
ƒ Power-on Sequence Control and Soft-Start
ƒ Brownout Protection
ƒ Interleaved PFC/PWM Switching
ƒ FAN4801/1S/2/2L Improve Efficiency at Light Load
ƒ fRTCT=4•fPFC=4•fPWM for FAN4800A and
FAN4801/1S
ƒ fRTCT=4•fPFC=2•fPWM for FAN4800C and
FAN4802/2L
Applications
ƒ Desktop PC Power Supply
ƒ Internet Server Power Supply
ƒ LCD TV, Monitor Power Supply
ƒ UPS
ƒ Battery Charger
ƒ DC Motor Power Supply
ƒ Monitor Power Supply
ƒ Telecom System Power Supply
ƒ 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 don’t 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
 

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