UC3842B-S08-T Просмотр технического описания (PDF) - Unisonic Technologies

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UC3842B-S08-T

HIGH PERFORMANCE CURRENT MODE CONTROLLERS

Unisonic Technologies 

UC3842B/3843B

„ APPLICATION INFORMATION(Cont.)

Current Sense Circuit

LINEAR INTEGRATED CIRCUIT

Peak current (IS) is equaled:

IS(MAX)=1.0V/RS

There should be a small RC filter to suppress switch transients.

Oscillator Waveforms and Maximum Duty Cycle

VREF 8

RT

RT/RC 4

CT

GND 5

LARGE RT

SMALL CT

SMALL CT

LARGE RT

V4

INTERINAL CLOCK

V4

INTERINAL CLOCK

CT (Oscillator timing capacitor) can be charged by VREF through RT and discharged by an internal current source. At

discharge time, the internal clock signal blanks the output to the low. Both oscillator frequency and maximum duty

cycle can be determined by Selection of RT and CT. All charge and discharge times can be calculated by the next

formulas:

tC=0.55 RT CT

tD=RTCTIn

⎜⎜⎝⎛

0.0063R T

0.0063R

− 2.7

T −4

⎟⎟⎠⎞

UNISONIC TECHNOLOGIES CO., LTD

www.unisonic.com.tw

7 of 11

QW-R103-012.D

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