UC3842A Просмотр технического описания (PDF) - Contek Microelectronics

Номер в каталоге

Компоненты Описание

производитель

UC3842A

CURRENT MODE PWM CONTROL CIRCUITS

Contek Microelectronics 

UC3842A /3843A LINEARINTEGRATED CIRCUIT

OSCILLATOR SECTION

8

4

5

Large RT

Small CT

RT

CT Small RT

Large CT

V4

INTERNAL

CLOCK

V4

INTERNAL

CLOCK

Dead time VS C

T(RT>5kW) Timing Resistance Vs Frequency

100

td (ms)

10

1

100

RT (k W)

10

CT=1nF

CT=2.2nF

CT=4.7nF

CT=10nF

CT=22nF

CT=47nF

CT=100nF

0.1

1

10

100

CT (nF)

1

10 2

10 3

10 4

10 5

10 6

Frequency (Hz)

SHUTDOWN TECHNIQUES

1kW

8

1

Shutdown

Shutdown

3

To current

Sense resistor

Shutdown Contek 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 accomplished by adding an SCR which be

reset by cycling Vcc below the lower UVLO

threshold. At this point the reference turns off

allowing the SCR to reset.

Contek Microelectronics Co.,Ltd.

5

CONTEK

http://www.contek-ic.com E-mail:sales@contek-ic.com

Share Link: