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F28026 Reset Accidently

Young Hu
Expert 4185 points


Hi,

My customer is doing whole system testing and found F28026 would reset when taking reactor short circuit testing. We found the 3.3V VDDIO would be oscillating for several cycles(the period is about 40ns) when the short circuit happened. You can find the scope snapshot as follows, and the channel 2 is the VDDIO of F28026, channel 3 is the Vcc of other MCU as main controller. The lowest voltage of VDDIO is about 1.6V. After that, C2000 would be reset and /XRS would be dropped, another MCU cannot be reset. So looks BOR triggered the reset and dropped /XRS. From the following link(https://e2e.ti.com/support/microcontrollers/c2000/int-c2000/f/175/p/391164/1382017#pi316725=1 ), it seems disabling the function of BOR cannot remove the reset.

Is there anything we can do to eliminate the reset? And is there any delay time(or blank time) from VDDIO reaching the trip point to drop the XRS?

 

Thanks.

Best regards,

Young

  • 0
    TI__Guru* 95315 points
    Young,
    1.6v is way below the Minimum Required operating voltage for this device, which is 2.97v. Masking the reset, if it were even possible, is not the correct solution/approach. I am more concerned about the severe disturbance on the VDDIO rail and device operating out of the datasheet limits (even momentarily). Are you able to share details of the reactor-short-circuit-testing and also the portions of the schematics that show power-supply decoupling offline with me? I think the correct approach would be to ensure the rails are within spec all the time.
  • 0
    TI__Guru 62975 points

    Young,

    To elaborate on Hareesh's comments, I suspect that the POR reset is also being triggered when the voltage droops that low.

    There is no flexibility with the POR reset because of legitimate concerns about logic state corruption inside the device below this trip level.  I think that allowing the device to reset as designed would be the safest course of action under this scenario.

    Is the primary concern that the F28026 is resetting or is it that the external controller MCU will not reset?  I'm not clear as to which behavior is the most critical for passing the short circuit test.

    -Tommy

  • 0 in reply to tlee
    TI__Expert 4185 points

    tlee said:

    Young,

    To elaborate on Hareesh's comments, I suspect that the POR reset is also being triggered when the voltage droops that low.

    There is no flexibility with the POR reset because of legitimate concerns about logic state corruption inside the device below this trip level.  I think that allowing the device to reset as designed would be the safest course of action under this scenario.

    Is the primary concern that the F28026 is resetting or is it that the external controller MCU will not reset?  I'm not clear as to which behavior is the most critical for passing the short circuit test.

    -Tommy

    Hi Tommy,

    Customer also found F28026 would reset during PFC starting up. their primary concern is F28026 is resetting.

    Thanks,

    Regards,

    Young

  • 0 in reply to Hareesh Janakiraman
    TI__Expert 4185 points
    Hi Hareesh,
    Fully understood that VDDIO was out of spec. I will send the schematics to you.

    Thanks,
    Young