LM3842A/3A/4A/5A
CURRENT MODE PWM CONTROLLER
FEATURES
8 SOP/ 8 DIP PIN Configulation
Compen
sation
VREF
8
7
6
5
● Automatic feed forward compensation
● Optimized for offline converter
● Double pulse suppression
1
2
Voltage
Feedback
Vcc
Current
Sense
● Current mode operation to 500 KHz
● High gain totem pole output
OUTPUT
3
4
RT/CT
GND
● Internally trimmed bandgap reference
● Undervoltage lockout with hysteresis
● Low start up current :< 0.3 mA
ORDERING INFORMATION
Device
Package
8 SOP
8 DIP
LM3842A/3A/4A/5A D
LM3842A/3A/4A/5A N
DESCRIPTION
The LM3842A is fixed frequency current-mode PWM controller. It is specially designed for Off-Line and
DC-to-DC converter applications with minimal external components.
This integrated circuit features a trimmed oscillator for precise duty cycle control, a temperature
compensated reference, high gain error amplifier, current sensing comparator, and a high current
totempole output ideally suited for driving a power MOSFET.
Protection circuitry includes built in under-voltage lockout and current limiting.
SIMPLIFIED BLOCK DIAGRAM
Vcc
5V
Undervoltage
VREF
⑧
Reference
Lockout
R
R
VREF
Undervoltage
Lockout
⑦ Vcc
Oscillator
RT/CT ④
VFB ②
⑥ Output
⑤ Ground
Latching
PWM
+
-
Error
Amplifie
③ Current
Sense
COMP ①
Input
ABSOLUTE MAXIMUM RATINGS (TA= 25℃)
Characteristic
Power Supply Voltage
Output Current
Symbol
Value
Unit
V
Vcc
I
30
± 1
A
VIN
ISINK
PD
Analog Inputes Voltage
Error Amp Output Sink Current
-0.3 to 5.5V
10
V
mA
Power Dissipation
1
W
℃
℃
Storage Temperature Range
Lead Temperature (soldering 5 sec)
Tstg
T
-65 to 150
260
HTC
1