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LM5170-Q1: Is HO to SW voltage fine with-2V spike and 4ns duration?

Part Number: LM5170-Q1
Other Parts Discussed in Thread: TIDA-01042, LM5170

Hi team,

In customer battery test projects by TIDA-01042, control board with LM5170 is usually connected to power stage board through connecters. As a result, the trace from HO/LO/SW/GND pins to MOSFET is long, which generates large negative spike. My customer found some HO pin were damaged after half a hour operation. They added the diode at HO and SW to clamp it. Below figures are how they measure it and the measured negative spike after diode added.  The negative spike duration is 1.6ns and peak is -1.76V. You could see the spike is larger than specified -1.5V of datasheet, but the time is much less than the specified 20ns. Is it safe to LM5170?

My customer will MP 56ku in this year, so they are very careful about this. Current solution of added diode can solve the damage issue in their test/pilot run, but they still would like to double confirm with our product line.

Thanks.

  • Hello Jerry,

    Switch node undershoots and overshoots are one of the most difficult parameters to measure. So thank you that you shared the measurement method as well as the scope plot and the schematic. This is great information.

    Is it possible that the customer is using a passive probe for this measurement? The capacitance of the probe will influence the measurement heavily, so if this is a passive probe, please ask the customer to redo the measurement with an active probe that has low capacitance. The customer might then observe a totally different value. I experienced this myself.

    If the measurement still shows less than -1.5V, I would recommend to exchange the diode with one that has a faster reaction time. It is possible that a fast recovery diode with a higher forward voltage is better than a Schottky diode in this specific case, but this needs to be measured.

    Best regards,
    Brigitte