UC2843BL-S08-R datasheet(6/8 Pages) UTC

6 / 8 page

UC2843B

LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

6 of 8

www.unisonic.com.tw

QW-R103-048.D



APPLICATION INFORMATION(Cont.)

Open-Loop Laboratory Test Fixture

In the open-loop laboratory test fixture, high peak currents and loads need grounding techniques. The transistor

and 5-kΩ potentiometer sample the oscillator waveform, applying an adjustable ramp to the ISENSE terminal. Timing

and bypass capacitors should be connected closely to the GND terminal in a single-point ground.

Shutdown Technique

The PWM controller can be shut down through two methods: the one is raising voltage (above 1 V) at ISENSE, the

other is pulling the COMP terminal below a voltage two diode drops above ground. Either method can leave the

output of the PWM comparator high (refer to block diagram). To reset the PWM latch is dominant so the output can

stay low in the case of the next clock cycle is coming and the COMP or ISENSE terminal is removed beyond this

shutdown condition. For example, an externally-latched shutdown can be accomplished by adding an SCR reset by

cycling VCC below the lower UVLO threshold. So the reference turns off then allows the SCR to reset at this

condition.

VREF

ISENSE

330Ω

1kΩ

500Ω

To Current-Sense

Resistor

Shutdown

COMP

UC2843BL-S08-R データシート(PDF) 6 Page - Unisonic Technologies