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TPS7A8300: Vout over abs max. rating

Zeming Kong
Expert 3515 points
Part Number: TPS7A8300

Hi team,

My customer is using TPS7A8300. And in his application, during the shutdown of Vin, Vout will show a voltage over Vin + 0.3V for about 310ms, while abs max.rating of output should be lower than Vin + 0.3V, will this damage the IC? If so, how to prevent this?

Best,

Zeming

  • 0
    TI__Mastermind 29270 points

    Hi Zeming,

    The internal ESD diodes will become forward biased under the customers operating conditions, which is not recommended.  We cannot recommend operating in this condition.  If the customer must operate in this scenario then they should strive to alleviate the stress on the ESD diodes as much as possible.  In addition to lowering the voltage as much as they can above 0.3V (0.31V is better than 0.4V, etc) they should reduce the current across the diode.  So a high series resistance or other mechanism to limit the current as much as possible is desirable (10uA is better than 1mA, etc).  Lastly they should reduce the time this elevated voltage and current is experienced across the diode.  10us is better than 1ms, etc.  This reduces the energy across the ESD diode when it is forward biased.

    Ultimately this is operating outside of our datasheet specifications so the customer will have to ensure that this device functions in their application as they need, if they use it in this manner.

    Thanks,

    - Stephen

  • 0 in reply to Stephen Ziel
    TI__Expert 3515 points

    Hi Stephen,

    Thanks a lot for your explanation.

    Could you provide data on the relationship between bias voltage and current increase of the ESD diode?

    I was wondering if they could use a external discharge circuit to solve this problem, will this make sense?

    Best,

    Zeming

  • 0 in reply to Zeming Kong
    TI__Mastermind 29270 points

    Hi Zeming,

    The IV curve of the ESD diode is not readily available, however it is usually proprietary data so I don't believe I can release that.

    I reread your question, and I mistakenly thought you were referring to another pin and not Vout.  If Vout exceeds Vin by 0.3V then it will not be an ESD diode, it will be the internal nonideal MOSFET body diode that will be forward biased.  Once that diode is forward biased, reverse current will flow in the MOSFET from Vout to Vin.  In this case we recommend to limit the current to 5% the abs max rating of the device.  For the TPS7A8300 that is 100 mA reverse current. 

    Thanks,

    - Stephen