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Current-mode PWM controller

UC3842A Internal Circuitry

Explore the internal circuitry and functional stages of UC3842A.

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Inside UC3842A

Reference, current comparator and a clocked PWM latch.

Compact UC3842A cutaway with UVLO, reference, oscillator, error amplifier, current comparator, latch and output driver.
Functional architecture; the external switching stage and current shunt are not inside this IC.

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Establish the references

UVLO controls startup. VREF supplies timing and the feedback reference.

Compare sensed current

COMP sets a threshold for ISENSE, bounded by the internal clamp.

Reset the PWM latch

A current trip ends the pulse; the next oscillator cycle allows a new one.

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