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TPS40170 Shootthrough Issue

James Fowkes
Prodigy 90 points

Hello,

I have  a TPS40107 design that I'm experiencing FET shoot-through on. Here's scope traces of both FET gates:

Blue trace is upper, yellow is lower. Lots of ringing on both gates.

Here's the schematic:

The design is for a 48V input, though I'm currently using 15V to prevent the FETs from burning out.

I've experimenting with changing the value of the RC snubber, but there is no/very little change to the behaviour of the circuit.

Thank you, any help is appreciated.

  • 0
    Prodigy 90 points
    Sorry for bumping this, I'd really like to get some guidance.

    Can anyone suggest anything? Is there more information I can provide?
  • 0 in reply to James Fowkes
    TI__Guru**** 191445 points
    Let me see if I can find someone to help.
  • 0
    TI__Mastermind 24075 points
    Hi,

    First, can you take C8 off?
    The blue trace in your waveform is the voltage between HS gate and GND, we need to check Vgs of high-side FET.
    Please measure the Vgs of high-side FET and low-side FET at the same time.
    If you don't have a differential probe to measure high-side Vgs, please use two probes to measure high-sidge gate and SW, then get Vg-Sw=Vgs.

    Thanks
    Qian
  • 0 in reply to Qian Chen
    Prodigy 90 points

    Sorry for delay in replying, I was diverted onto other projects.

    We don't have a differential probe, so had to use math function on the 'scope. As requested, here's traces for highside and lowside Vgs:

    On both images:

    Channel 1, yellow: Switch node

    Channel 2, blue: Highside gate

    Channel 3, pink: lowside gate

    Math, purple: Ch.2 - Ch.1

    I don't know how to interpret these traces, so hopefully they can provide information that helps you.