October 2011
FAN4800AU/CU
PFC/ PWM Controller Combination
Features
Description
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Pin-to-Pin Compatible with ML4800, FAN4800,
CM6800, and CM6800A
The highly integrated FAN4800AU/CU parts are
specially designed for power supplies that consist of
boost PFC and PWM. They require very few external
components to achieve versatile protections and
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 current or Voltage Mode. In
Voltage Mode, feed-forward from the PFC output bus
can reduce secondary output ripple.
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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
Line Sagging Protection
To evaluate FAN4800AU/CU for replacing existing
FAN4800A/C, FAN4800AS/CS, old version FAN4800
and ML4800 boards, six things must be completed
before the fine-tuning procedure:
1. Change RAC resistor from the old value to a higher
resistor value: 6M to 8M.
2. Change RT/CT pin from the existing values to
RT=6.8K and CT=1000pF to have fPFC=64kHz and
f
PWM=64kHz.
fRTCT=4•fPFC=4•fPWM for FAN4800AU
fRTCT=4•fPFC=2•fPWM for FAN4800CU
3. The VRMS pin needs to be 1.224V at VIN=85VAC for
universal input application with line input from
85VAC to 270 VAC
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Applications
4. Change ISENSE pin filter from the exiting values to
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Desktop PC Power Supply
Internet Server Power Supply
LCD TV/ Monitor Power Supply
UPS
RFilter=51 and CFilter=0.01µF for higher bandwidth.
5. At full load, the average VVEA must be ~4.5V and
ripple on VVEA needs to be less than 400mV.
6. For the SS pin, the soft-start current has been
reduced to half the FAN4800 capacitor.
Battery Charger
There are two differences from FAN4800AS/CS to
FAN4800AU/CU:
DC Motor Power Supply
Monitor Power Supply
Telecom System Power Supply
Distributed Power
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Add Line Sagging Protection
Fix Inductance Current Instability during AC Cycle
Drop Test
Related Resources
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AN-8027 — FAN480X PFC+PWM Combination
Controller Application
© 2011 Fairchild Semiconductor Corporation
FAN4800AU/CU • Rev. 1.0.0
www.fairchildsemi.com