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BQ76942: The impact of temperature on the lifespan of the BQ76942

Duncan wang
Prodigy 50 points
Part Number: BQ76942

 

We are evaluating the impact of temperature on the lifespan of the BQ76942. We have noticed that in the datasheet, the Functional temperature is 85 degrees Celsius, while the junction temperature is 150 degrees Celsius.
In the calculations for lifespan and MTBF, should we refer to 85 degrees or 150 degrees?
Please note that in practice, our product will not allow the BQ76942 to operate above 85 degrees; we will shut down the product as it approaches 75 degrees.

  • 0
    TI__Mastermind 42060 points

    Hello Duncan,

    I am going to look into this.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 50 points

    Hi Luis, 

    Is there any progress on this issue?
  • 0
    TI__Mastermind 42060 points

    Hello Duncan,

    It's probably fine to do 85C or 125C for this.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 50 points

    Hi Luis:

    I don't quite understand, could you explain it more clearly? why not juction temperature 150degC?
  • 0 in reply to Duncan wang
    TI__Expert 5645 points

    Hi Duncan, 

    The junction temperature spec refer to the maximum junction the part can tolerate on the Absolute Maximum Ratings, the 85C represent the maximum ambient temperature the device was characterized and where the specs (Electrical Characteristics) are guarantee and the part is expected to be functional. 

    For lifespan and MTB you want to get an average operating range of the device, you can use an ambient temperature of 85C as that's where your systems will be operating. You can also us the datasheet thermal information and your systems power dissipation to calculate the junction temperature of the die when ambient is 85C, or measure the junction temperature on your board while dissipating max power. An alternative or common practice will be using a 125C as junction will be a very good representation of the device operating.

    The device shall never be exposed to 150deg junction for a lifespan, so that'll be way to extreme to get average life information, so 125C is a more conservative estimate if you want to get worse case operational lifespan or MTB. Hope this helps. 

    Best regards, 

    Arelis G. Guerrero