General
Description
The
CM6805A
is
the
Green-Mode
PFC/PWM
Combo
controller
for Desktop
PC
and
High
Density
AC
Adapter.
For
the
power
supply,
it’s
input
current
shaping
PFC
performance
could
be
very
close
to
the
performance
of the CM6800
or
ML4800
leading
edge
modulation
average
current topology.
CM6805A
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
CM6805A
includes
circuits
for
the
implementation
of
a leading
edge
modulation,
input
current
shaping
technique
“boost”
type
PFC and
a trailing edge modulation
current, PWM.
The
CM6805A’s
PFC
and
PWM
operate
at
the
same
frequency,
100kHz.
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.
PFC has
a
PFCOFFB
pin
which
can
use
for
AC
brown
out application
and determine
the GMth
to turn off
PFC.
---------------------------------------------------------------------------------------------------------------------------------------------
Features
- 10-Pin SOIC package
- Use RAC as the
Startup resistor which
can be > 2000K or
higher at
IAC pin
- It can use the HV
bipolar
to start
up the chip
and it
helps
green mode.
- Easy to
configure into Boost Follower
- 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, Precision -1V
PFC
ILIMIT,
PFC
Tri-Fault
Detect comparator
to meet
UL1950
- 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
- Exact 50% PWM maximum
duty
cycle
- UVLO, REFOK, and brownout
protection
- Digital PFC and
PWM soft
start,
~10mS
- Precision PWM
1.5V
current
limit
for
current
mode
operation
- PFCOFFB
pin
to
sense
light
load
to
turn
off
PFC
or PFCOFFB
pin
to
sense
Input
voltage
as
AC
Brown
Out
