CM6903A
Low Pin Count PFC/PWM C
ONTROLLER
C
OMBO
GENERAL DESCRIPTION
The CM6903A is a space-saving PFC-PWM controller
for power factor corrected, switched mode power supplies
that offers very low start-up and operating currents. For the
power supply less than 500Watt, its input current shaping
PFC performance could be very close to CM6800 or
ML4800 architecture.
Power Factor Correction (PFC) offers the use of
smaller, lower cost bulk capacitors, reduces power line
loading and stress on the switching FETs, and results in a
power supply fully compliant to IEC1000-3-2 specifications.
The CM6903A includes circuits for the implementation of a
leading edge, input current shaping technique “boost” type
PFC and a trailing edge, PWM.
The CM6903A’s PFC and PWM operate at the same
frequency, 67.5kHz. A PFC OVP comparator shuts down
the PFC section in the event of a sudden decrease in load.
The PFC section also includes peak current limiting for
enhanced system reliability.
FEATURES
Patent
Number
#5,565,761,
#5,747,977,
#5,742,151,
#5,804,950, #5,798,635
Pin to pin compatible with FAN6903/4
Enable lowest BOM for power supply with PFC
Internally synchronized PFC and PWM in one IC
Patented slew rate enhanced voltage error amplifier with
advanced input current shaping technique
Universal Line Input Voltage
CCM boost or DCM boost with leading edge modulation
PFC using Input Current Shaping Technique
Feed forward IAC pin to do the automatic slope
compensation
PFCOVP, PFC VCCOVP, Precision -1V PFC ILIMIT,
Tri-Fault Detect comparator to meet UL1950
No bleed resistor required
Low supply currents; start-up: 100uA typical, operating
current: 2mA typical.
Synchronized leading PFC and trailing edge modulation
PWM to reduce ripple current in the storage capacitor
between the PFC and PWM sections and to reduce
switching noise in the system
VINOK Comparator to guarantee to enable PWM when
PFC reach steady state
High efficiency trailing-edge current mode PWM
UVLO, REFOK, and brownout protection
Digital PWM softstart: CM6903A (10ms)
Precision PWM 1.5V current limit for current mode
operation
APPLICATIONS
Desktop PC
AC Adaptor
Open Frame
PIN CONFIGURATION
SIP-09 (Z09)
Front View
DC ILIMIT
PW MOUT
PFCOUT
ISENSE
VEAO
GND
VCC
VFB
1
2
3
4
5
6
7
8
2008/10/20 Rev1.4
Champion Microelectronic Corporation
IAC
9
Page 1
CHAMP [ CHAMPION MICROELECTRONIC CORP. ]
