January 2014
?2010 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FAN4800AS/CS/01S/02S " Rev. 1.0.2
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
?   f
RTCT
=4"f
PFC
=4"f
PWM
for FAN4800AS/01S
?   f
RTCT
=4"f
PFC
=2"f
PWM
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 R
AC
resister from the old value to a higher
resister: between 6 M?to 8 M?
2.    Change RT/CT pin from the existing values to
R
T
=6.8k? 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 from line input from
85 V
AC
to 270 V
AC
.
4.    At full load, the average V
VEA
needs to be ~4.5 V
and the ripple of V
VEA
needs to be less than
400 mV.
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 19 V.