April 2009
FAN4800A/C, FAN4801/1S/2/2L
PFC/PWM Controller Combination
Features
Description
The
highly
integrated
FAN4800A/C
and
Pin-to-Pin Compatible with ML4800 and FAN4800
and CM6800 and CM6800A
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.
PWM Configurable for Current-Mode or
Feed-Forward Voltage-Mode Operation
Internally Synchronized Leading-Edge PFC and
Trailing-Edge PWM in one IC
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.
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
Peak Current Limiting for PFC
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.
Cycle-by-Cycle Current Limiting for PWM
Power-On Sequence Control and Soft-Start
Brownout Protection
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:
Interleaved PFC/PWM Switching
1. Change RAC resister from the old value to a higher
FAN4801/1S/2/2L Improve Efficiency at Light Load
resister: between 6MΩ to 8MΩ.
fRTCT=4•fPFC=4•fPWM for FAN4800A and
FAN4801/1S
2. Change RT/CT pin from the existing values to
RT=6.8KΩ and CT=1000pF to have fPFC=64KHz,
PWM=64KHz.
f
fRTCT=4•fPFC=2•fPWM for FAN4800C and
FAN4802/2L
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.
Applications
Desktop PC Power Supply
4. At full load, the average VEA needs to ~4.5V and
the ripple on the VEA needs to be less than 400mV.
Internet Server Power Supply
LCD TV, Monitor Power Supply
UPS
5. Soft-Start pin, the soft-start current has been
reduced to half from the FAN4800 capacitor.
Battery Charger
DC Motor Power Supply
Monitor Power Supply
Telecom System Power Supply
Distributed Power
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. 1.0.2
www.fairchildsemi.com
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