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TPS65910: Negative maximum Input voltage rating on the Switching the switching output of DC-DC 1 &2

Krushang Gandhi
Prodigy 90 points
Part Number: TPS65910
Other Parts Discussed in Thread: TPS650861

Hi Team,

We just want o know the negative maximum input voltage rating for the Switching output of the internal DC-DC output from the PMI(TPS65910). Please let us know we had gone through the datasheet but it is not clearly specified in Electrical Specification Section. We are trying to tune Snubber on the output voltage rail of 1.1V and 1.5V to reduce Overshoot and undershoot observed as per reference waveform attached here with.

Please let us know the negative voltage limit for switching node so that we can make decision for the requirement of Snubber circuit tunning.

VDD_CORE_1V1 Switching Waveform

VDD_DDR_1V5 Switching Waveform

Kind Regards,

Krushang Gandhi

  • 0
    TI__Mastermind 30260 points

    The minimum negative voltage for most pins on every IC is listed as -0.3V, but this is the minimum voltage that can be applied externally. The TPS65910 lists -0.3V for all pins in the Absolute Maximum Ratings table on page 10 of the datasheet.

    The switching node is a special pin, and the overshoot/undershoot on the switching node is generated by the PMIC itself. The undershoot is normal and expected and usually will not cause harm to the IC.

    If you are designing a snubber circuit, you can tune it to try to minimize ringing on the rising edge that causes the overshoot. There should be a frequency component of the ringing that is easy to identify. I would estimate the period is 4ns, so the frequency is approximately 250MHz.

  • 0 in reply to Brian Berner
    Prodigy 90 points

    Hi Brian,

    Thanks for the inputs.

    As per the test results, we are getting negative maximum voltage of approximately -1.2V. If we don't want to tune snubber circuit, then does it will be going to damage or create reliability issue for  TPS65910 ?

    Regards,

    Krushang Gandhi

  • 0 in reply to Krushang Gandhi
    TI__Genius 17380 points

    Hi Krushang,

    Brian is out of office this week so I will help to cover.

    -1.2V is reasonable, some of our newer products like TPS650861 have a spec for these small transients set to -2 V so I would not expect snubber to be necessary for -1.2V.