UC3842A/3843A

LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

7 of 9

www.unisonic.com.tw

QW-R103-002.F

SHUTDOWN TECHNIQUES

8

3

1k

Ω

1

Shutdown

To current

Sense resistor

Shutdown

Shutdown UTC UC3842A can be accomplished by two methods; either raise pin 3 above 1V or pull Pin 1 below a

voltage two diode drops above ground. Either method caused the output of PWM comparator to be high(refer to

block diagram).The PWM latch is reset dominant so that the output will remain low until the next clock cycle after the

shutdown condition at pins 1 and/or 3 is removed . In one example, an externally latched shut –down may be