LM7480-Q1: OVP Hysteresis Issue

Nick Wase

Part Number: LM7480-Q1

Hello,

I found the OVP hysteresis seems to not be functional. I see a clean UVLO trigger and reset. But the OVP jitters from 50.6V to 20V. I am using a 0.1uF capacitor across VS and CAP, per the data sheets instructions on Table 6-1. Pin Functions and Section 9.5 Application Examples.. See below for a scope shot of OVP being triggered and then set completely once the top level threshold is passed. Is this expected? Can this be corrected?

Thank you,

Nick

over 3 years ago

0 Praveen GD over 3 years ago

TI__Guru 57737 points

Hi Nick,

Can you please share your schematics.

Is OV Protection set to cut off or clamp mode?

what is the signal captured in the waveform? Is it output voltage?

What is the test condition while you captured the waveform?

0 Nick Wase over 3 years ago

Intellectual 415 points

Hi Praveen,

Do you mind if I send the schematic to you in private? I can't show them publicly on the forum.

I believe OV protection is set to cut-off. The OV voltage divider uses SW as the input like the datasheet example on page 1, "Ideal Diode with 200-V Load Dump Protection".

The signal captured is from the C pin, Cathode of the ideal diode.

The test condition was evaluating the OVP circuit. 42V was applied to the input and then was slowly rolled up to about 50V before the OVP completely triggered. Between about 49.6V and 50.8V this oscillation was occurring.

Thank you,

Nick