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TPS63024: L2 pin minimum absolute voltage

Nariaki Ogasawara
Intellectual 1215 points
Part Number: TPS63024

Hi team,

 The customer measured the minimum voltage of L2 pin at the boost operation is -0.8V,

 The L2 absolute voltage in datasheet is -0.3V and note says (4) AC transient voltage rating, so -0.8V is over the absolute voltage
 My understanding is that the inductor tries to sustain the current when the internal N - FET goes from ON to OFF, so the L2 voltage will be -0.8 V due to the body diode or ESD.

 I would like to confirm what mean the -0.3V of Absolute Maximum Ratings?

Regards,

Ogasawara 

  • 0
    TI__Expert 7925 points
    Hello Ogasawara,

    Please see the following thread, the same applies here:
    e2e.ti.com/.../2647207

    What kind of probe was used and where were the probe tips connected?

    Best regards,
    Milos
  • 0 in reply to Milos
    TI__Intellectual 1050 points

    Hi Milos,

    I think there is dead time which both of high-side and low-side FETs are turned off, and we can see -0.7V on L2 pin at this period. This is made by Vf drop of low side FET's body diode, and this should be normal behavior. We can see this Vf drop even if we use optimized probe and measurement environment.
    The absolute max mentions at L2 pin is -0.3V. We need to clarify this inconsistency.
    What Ogasawara-san and I are asking is the undershoot of the red circle below.

    Thanks,
    Nobuhiko Wasa

  • 0 in reply to Nobuhiko Wasa
    TI__Expert 7925 points

    Hi Wasa,

    Thank you for the screenshot. You are right, during dead time the body diode will conduct and you will have negative undershoots. This is normal behavior of switching converters and will not damage the part.

    The -0.3 V in absolute maximum ratings refer to constant DC voltage applied to pin, and not short pulses typical for normal switching operation. Otherwise, you can observe lower voltage due to body diode conduction and also some superimposed short (<10 ns) spikes due to discharge of internal parasitic inductance.

    Best regards,
    Milos

  • 0 in reply to Nobuhiko Wasa
    TI__Expert 7925 points
    Hello Wasa,

    We haven’t heard back so we're assuming your issue is resolved. If not, just post a reply below, or create a new thread if the thread has locked due to time-out.

    Thanks and regards,
    Milos
  • 0 in reply to Milos
    TI__Intellectual 1050 points

    Hi Mios,

    Sorry for late update.
    The customer accepted our explanation. So this topic can be closed.
    Please update the datasheet to clarify it if you have a chance to revise.

    Thanks,
    Nobuhiko Wasa