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TPS7B4254-Q1: Behavior when applying 30V at FB pins in battery short condition

Takashi Onawa
Genius 13200 points
Part Number: TPS7B4254-Q1

Hi Team,

I'm interested in TPS7B4254-Q1 for external sensor power supply.

In my application, I need to consider up to 30V as battery short condition, but the recommended operation rage for FB pin is up to 18V regarding to the datasheet.

Do you recommend to put FB divider for such the requirement? Or can I use TPS7B4254-Q1 with connecting FB pin to output line directly?

Regards,

Takashi Onawa

  • 0
    TI__Intellectual 825 points

    Hi Takashi,

     In this condition, you cannot use the TPS7B254-Q1 with FB pin directly connected to the output line. 

     You can put divider resistors like in Fig.25 (page13 of datasheet) according to your desired output voltage relative to the Vref voltage (voltage input at ADJ pin).

    Regards,

    Chito

  • 0 in reply to Chito Tapia
    TI__Genius 13200 points

    Hi Chito-san,

    >you cannot use the TPS7B254-Q1 with FB pin directly connected to the output line. 

    Do you mean that the device will get a damage by applying 30V at FB pin?

    Regards,

    Takashi Onawa

  • 0 in reply to Takashi Onawa
    TI__Intellectual 825 points

    Hi Takashi,

       We normally advise customers to stay within the recommended operating conditions that why I don't recommend exposing the FB pin to 30V since it is way above the 18V recommended max voltage. However, looking at the abs max ratings for this pin (FB), it is rated at 45V so it is likely that it will not get damaged when exposed to only 30V.

      We'll try to emulate your short circuit test on the bench using on EVM just to confirm. Do you have any specific setup conditions in mind like what is Vin, Vadj, Vout during normal condition? then what is the setup condition during the the shorts circuit test?

     

    Regards,

    Chito

  • 0 in reply to Chito Tapia
    TI__Intellectual 825 points

    Hi Takashi,

     We setup the following conditions on the bench using the EVM and the device survived with no indication of damage. In summary, the FB pin (and even the ADJ) when shorted to 30V will not be damaged. I hope it answered your question.

    Setup 1:

    Vin, Vout, FB are shorted together to 30V

    Adj = 18V

    setup duration: 3hrs

    Result:  Device is still good.

    Setup 2:

    Vin, Vout, FB, Adj are shorted together to 30V

    setup duration: 12+hrs

    Result:  Device is still good.

     Regards,

    Chito

  • 0 in reply to Chito Tapia
    TI__Genius 13200 points

    Hi Chito-san,

    Thanks for checking it.
    OK, I understood.

    Regards,

    Takashi Onawa