FAIRCHILD KA3842AC, KA3842AE Service Manual
KA3842AC/KA3842AE
SMPS Controller
KA3842AC/KA3842AE SMPS Controller
March 2006
Features
Low start current 0.2mA (Typ.)
Operating range up to 500kHz
Cycle by cycle current limiting
Under Voltage Lock Out (UVLO) with hysteresis
Short shutdown delay time: Typ.100ns
High current totem-pole output
Output swing limiting: 22V
Ordering Information
Operating
Part Number
KA3842AC -0 to +70°C Yes 8-DIP Tube
KA3842AE
Temp. Range Pb-Free Package Packing Method
Description
The KA3842AC/KA3842AE are fixed PWM controllers
for Off Line and DC to DC converter applications. The
internal circuits include UVLO, low start up current, temperature compensated reference, high gain error amplifier, current sensing comparator, and high current totem
pole output for driving a POWER MOSFET. Also
KA3842AC/KA3842AE provides low start up current
below 0.3mA and short shutdown delay time, typically
100ns. The KA3842AC/KA3842AE has a UVLO threshold of 16V(on) and 10V(off). The KA3842AC/KA3842AE
can operate within a 100% duty cycle.
1
8-DIP
©2006 Fairchild Semiconductor Corporation 1 www.fairchildsemi.com
KA3842AC/KA3842AE Rev. 1.0.1
Internal Block Diagram
8
V
REF
Internal
Bias
1/2 V
REF
2
V
FB
R
C.S
T/CT
1
3
4
COMP
5V
V
REF
Error Amp
+
-
OSCILLATOR
SET/
RESET
Good LOGIC
1/3
1V
C.S
Comp.
UVLO
PWM
LATCH
R
S
T
29V
22V
7
V
5
GND
PWR
7
V
6
OUTPUT
PWR
5
GND
KA3842AC/KA3842AE SMPS Controller
CC
C
KA3842AC/KA3842AE Rev. 1.0.1
2 www.fairchildsemi.com
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