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Current-mode PWM controller

UC3842A Working Principle

Learn how UC3842A works with an illustrated explanation and practical readings.

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UC3842A at a glance

Follow the labeled connections and functional stages

UC3842A working principle: illustrated functional stages, basic circuit and connections
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How it works

3 stages · Explore one step at a time

Step 1 / 3

Cross the startup threshold

VCC must first reach the start threshold. After startup, hysteresis permits operation at a lower voltage.

Step 2 / 3

Set the peak-current demand

The error amplifier compares FB with 2.5 V. COMP programs the current-comparator trip point, up to the internal limit.

Step 3 / 3

Terminate the pulse

A sufficiently high ISENSE signal resets the PWM latch. Oscillator blanking also limits maximum duty.

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