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TPS22916: Resistor for VIN Removal Case

McKenna Strambi
Intellectual 1410 points
Part Number: TPS22916

Tool/software:

Hi expert,

For TPS22916BYFPR, if we use a resistive divider on input for the enable, It's not clear how strong of a pull down we may need to ensure it turns off if the output is powered and input source goes away
I know it has QOD but if VIN is suddenly removed, any risk that this part would remain on?
How strong should the resistive string to be sure it turns off and achieves the 10nA leakage?

Thank you!

McKenna

  • 0
    TI__Mastermind 31261 points

    Hello McKenna,

    I have seen pull-down resistor at ON pin to make sure it's grounded not floating. pull down ranges from 10K to 100k range.

    On VIN pin pull down is not required. 

    Thanks
    Amrit 

  • 0 in reply to Amrit Jit
    TI__Intellectual 1410 points

    Hi Amrit,

    Customer is more so asking how strong should the resistive string to be sure it turns off and achieves the 10nA leakage?
    So, if there is no resistors required, can the 10nA leakage be achieved during off?
    If not, if 10k to 100k is used, can the 10nA leakage be achieved during off?
    Can you help to provide answer today?

    Thank you!

    McKenna

  • 0 in reply to McKenna Strambi
    TI__Intellectual 1410 points

    It looks like there is an internal resistor that may be helping out with this functionality but I'm not 100% sure - please clarify for this use case.

    Thank you!

    McKenna

  • 0 in reply to McKenna Strambi
    TI__Mastermind 31261 points

    Hello Mckenna,

    There is smart pull-down resistance which will be inserted when VON< VIL to prevent ON pin from floating.

    Smart pull down value is 750 kOhms. You don't need additional pull-down on ON pin.

    Thanks 
    Amrit 

  • 0 in reply to Amrit Jit
    TI__Intellectual 1410 points

    Hi Amrit,

    Got it. 

    The main question is: VIN goes high Z, VOUT remains powered, will leakage from VOUT flow to VIN and keep VIN high?
    When VIN goes away, there is nothing driving it to 0V. If the pull down is weak, it does not require very much leakage from VOUT-> VIN to keep it above 1.2V at EN. We can calculate it based on the resistor values, but the important thing to understand is the leakage structure back and what disables it.

    Please let me know your thoughts.

    Thanks!

    McKenna

  • 0 in reply to McKenna Strambi
    TI__Mastermind 31261 points

    Hello McKenna,

    Is VIN attached to ON pin?

    Device turn ON based on voltage on ON pin. VIN pin goes high will not turn the device ON.

    Let's discuss this on today webEx meeting.

    Thanks 
    Amrit