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TPS53219A: ENABLE pin voltage has a step during Vin rising

user4979989
Intellectual 2800 points
Part Number: TPS53219A

Hi team,

My customer designs TPS53219A, the enable pin comes from a resistor divider and the supply is 12V input voltage.

But during 12V is rising, we measured the enable voltage has a step.

Before enable step up, at this moment the Vin is ~3V and enable pin is ~0.5V to 0.6V.

Could you let me know if there is any reason for it?

Thank you.

The waveform is as below, Blue is enable and Green is Vin 12V.

Regards,

Allen

  • 0
    TI__Expert 5900 points

    Allen,

    The EN turn off threshold is around 0.5V so i think its the hysterisis that you see when started up with a slow ramp. This is nothing to be worried about since the EN threshold is around 1.4V.

    Regards,

    Mathew

  • 0 in reply to Mathew Jacob1
    TI__Intellectual 2800 points

    Hi Mathew,

    We changed the resistors to lower value (56.2k and 12.4k) but kept the same ratio.

    The enable waveform become smooth and there is no a step found.

    In power up the enable rises from 0V, the hysterisis causes enable step up in 0.5V, but the enable high threshold is 1.7V.

    In power down the enable should also see a step down in 0.5V caused by hysterisis? But the enable pin high threshold is still 1.7V.

    Even without hysterisis when enable is 0.5V, I think it's still fine if customer changes resistors to lower value?

    Please let me know if any concerns.

    Actually I told customer the step is fine but they still want to get smooth waveform.

    Thanks.

    Regards,

    Allen

  • 0 in reply to user4979989
    TI__Expert 5900 points

    Allen,

    That is a good change to make anyway (lower resistors for EN divider). I would recommend that.

    Regards,

    Mathew

  • 0 in reply to Mathew Jacob1
    TI__Intellectual 2800 points

    Hi Mathew,

    Thank you.

    One more quick question, as you mentioned the enable threshold is 1.4V.

    In the datasheet EC table, the enable threshold is 1.7V(0C~85C), 1.8V(-40C~85C) minimum.

    In feature description 7.3.1, the enable threshold typically is 1.4V.

    Which one is correct?

    Allen

  • 0 in reply to user4979989
    TI__Expert 5900 points

    Allen,

    The EC table thresholds are guaranteed min. The typ threshold is 1.4V. So for a design the voltage at the EN should be above the min value as per good design practice. In other words the resistor dividers should be set for >1.8V at the lowest input voltage.

    Regards,

    Mathew