January 2014
?2011 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FAN4800AU/CU " Rev. 1.0.1
FAN4800AU/CU
PFC/ PWM Controller Combination
Features
?   Pin-to-Pin Compatible with ML4800, FAN4800,
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
?   Line Sagging Protection
?   f
RTCT
=4"f
PFC
=4"f
PWM
for FAN4800AU
?   f
RTCT
=4"f
PFC
=2"f
PWM
for FAN4800CU
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   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.
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.
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 R
AC
resistor from the old value to a higher
resistor value: 6 MW to 8 MW.
2.    Change RT/CT pin from the existing values to
R
T
=6.8 KW and C
T
=1000 pF to have f
PFC
=64 kHz
and f
PWM
=64 kHz.
3.    The VRMS pin needs to be 1.224 V at V
IN
=85 V
AC
for universal input application with line input from
85 V
AC
to 270 V
AC
.
4.    Change ISENSE pin filter from the exiting values to
R
Filter
=51 W and C
Filter
=0.01 礔 for higher bandwidth.
5.    At full load, the average V
VEA
must be ~4.5 V and
ripple on V
VEA
needs to be less than 400 mV.
6.    For the SS pin, the soft-start current has been
reduced to half the FAN4800 capacitor.
There are two differences from FAN4800AS/CS to
FAN4800AU/CU:
?   Add Line Sagging Protection
?   Fix Inductance Current Instability during AC Cycle
Drop Test