BETAUC3842ACurrent-mode PWM controller
Start a pulse. Measure current. End it at the threshold.
UC3842A is a current-mode PWM controller with an oscillator, voltage-error amplifier, current comparator, latch and gate driver. It begins a switching pulse with the oscillator and ends it when the sensed current reaches the threshold requested by the feedback loop. This variant uses a nominal 16 V startup threshold and a 10 V turn-off threshold. It can operate near full duty cycle; it must not be confused with the lower-startup UC3843A or the half-duty UC3844A and UC3845A variants. The example uses an 18 V bench supply, an RC oscillator and an adjustable low-voltage signal at ISENSE. It demonstrates pulse truncation on a scope without a power MOSFET, transformer or mains connection. The selected eight-pin packages keep the same electrical pin numbers.
