January 2011
?2008 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FAN4800A/C, FAN4801/02/02L " Rev. 1.0.3 1
FAN4800A/C, FAN4801/02/02L
PFC/PWM Controller Combination
Features
?   Pin-to-Pin Compatible with ML4800 and FAN4800
and 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
?   Peak Current Limiting for PFC
?   Cycle-by-Cycle Current Limiting for PWM
?   Power-On Sequence Control and Soft-Start
?   Brownout Protection
?   Interleaved PFC/PWM Switching
?   FAN4801/02/02L Improve Efficiency at Light Load
?   f
RTCT
=4"f
PFC
=4"f
PWM
for FAN4800A and FAN4801
?   f
RTCT
=4"f
PFC
=2"f
PWM
for FAN4800C and
FAN4802/02L
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
Description
The highly integrated FAN4800A/C and FAN4801/02/2L
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   FAN4801/02/02L   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. Brownout protection and
PFC   soft-start   functions   are   not   in   ML4800   and
FAN4800.
To evaluate FAN4800A/C, FAN4801/02/2L 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 6MW to 8MW.
2.    Change RT/CT pin from the existing values to
R
T
=6.8KW and C
T
=1000pF to have f
PFC
=64KHz,
f
PWM
=64KHz.
3.    VRMS pin needs to be 1.224V at V
IN
=85 V
AC
for
universal input application from line input from
85V
AC
to 270 V
AC
. Both poles for the V
rms
of
FAN4801/02/02L dont need to substantially slower
than FAN4800; about 5 to 10 times.
4.    At full load, the average V
EA
needs to ~4.5V and the
ripple on the V
EA
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
?
AN-8027 - FAN480X PFC+PWM Combination
Controller Application