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TPS25921 question for TSD temperature variation and reliability after TSD working

Kazuya Nakai59
Guru 21595 points

 Hello guys,

 Our customer wants to use TPS25921 to protect a actuator driver when the actuator terminals are shorted.

 But they have the following questions about TSD of the device .

 Could you tell me your comments for the questions?

 1. When RILIM is 95.3kohm, TPS25921 current limit value is set to 1A.

     Then if the output load is shorted to GND, the device heats and the device temperature

    reachs to TSD threshold level (155C typ). After that, the switch which connects between IN and OUT terminal

    is turned off by TSD function.

     The customer wants to know the TSD accuracy. What is the maximum/minimum temperature of the TSD threshold level?

 2. What is TPS25921 life time by design with no TSD working? Our customer life time target is 13 years.

     Can the device meet the life time target?

 3. After TSD works 1 time, is the device reliability changed? Can our customer continue to use the device?

     Or should they replace the device with new one to meet their life time target?

     Also is the device life time reduced after TSD working?

 

Your reply would be very appreciated.

Best regards,

Kazuya Nakai.

 

  

 

 

  • 0
    TI__Intellectual 2800 points

    Hi Nakai-san,

    Please see my response here:

    1. When RILIM is 95.3kohm, TPS25921 current limit value is set to 1A.

        Then if the output load is shorted to GND, the device heats and the device temperature

       reachs to TSD threshold level (155C typ). After that, the switch which connects between IN and OUT terminal

       is turned off by TSD function.

        The customer wants to know the TSD accuracy. What is the maximum/minimum temperature of the TSD threshold level?

    [VN] Expected min, max TSD thresholds are: 145(min), 155(typ), 165(max)

    2. What is TPS25921 life time by design with no TSD working? Our customer life time target is 13 years.

        Can the device meet the life time target?

    [VN] Here is the reliability data link http://www.ti.com/quality/docs/estimator.tsp?OPN=TPS25921AD&partNumber=TPS25921AD&partType=tiPartNumber#resultstable

    3. After TSD works 1 time, is the device reliability changed? Can our customer continue to use the device?

        Or should they replace the device with new one to meet their life time target?

        Also is the device life time reduced after TSD working?

    [VN] Reliability will not change after one TSD event, customer can continue to use the device. Typically TSD event is transient in nature. Since average die temperature during fault is less than 125degC, reliability is not affected.

    Regards,

    Venkat

  • 0 in reply to Venkata Nandam
    Guru 21595 points
    Hi Venkat,

    Thank you for your reply.

    Could I ask again?
    Is TPS25921 reliability not changed even if TSD is occured many times (For example 10 times, 100 times or 1000times) not one?

    Thank you again and best regards,
    Kazuya Nakai.
  • 0 in reply to Kazuya Nakai59
    TI__Intellectual 2800 points

    Hi Nakai-san,

    Reliability change depends upon no of hours junction is operated at TSD temperature (155degC Typ). If the output is shorted to ground, with 12V Vin and 1A current limit, the device dissipates 12W and enters thermal shutdown in 1ms time. After entering thermal shutdown, it takes 150ms to cool down the junction and re-try again.

    Based on above conditions, if we assume that short persists for 365 days, no of hours junction operates at TSD temp is only 58. Reliability change for such small no of hours of operation at TSD temp is minimal.

    Regards,

    Venkat