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Original question:

TPS92630-Q1: TPS92630-Q1 Thermal Foldback programming

TPS92630-Q1: Question about operation in thermal foldback mode

Alan O
Mastermind 32575 points
Part Number: TPS92630-Q1

My customer is looking into using the TPS92630 LED driver in a scenario where, at high ambient temperatures, it is possible to operate the driver in the thermal foldback mode.

Is there any reliability or lifetime concern with operating the driver in this way, or does the protection mechanism sufficiently protect the device?

I believe this shouldn’t be an issue as long as the IC power dissipation using thermal foldback can maintain junction temperature below Tj-max spec of 150degC at max ambient temp and avoid continuous cycling into overtemperature shutdown mode - is this understanding correct?  Is it sufficient to estimate the Ptotal and Tj using the equations in section 10.4.1 in the datasheet?

Thanks,
Alan

  • 0
    TI__Genius 16660 points

    Hi,

    1)For thermal foldback mode, you need to choose the suitable resistor to connect the TEMP pin.

    2)I don't understand this part, please explain about this part.

    I believe this shouldn’t be an issue as long as the IC power dissipation using thermal foldback can maintain junction temperature below Tj-max spec of 150degC at max ambient temp and avoid continuous cycling into overtemperature shutdown mode

    3) the equations in 10.4.1 is sufficient in normal situation. If you have more concerns, please tell us more details.

  • 0 in reply to Zhiqian Wu
    TI__Mastermind 32575 points

    Assuming a suitable resistor is connected to the TEMP pin to set the thermal foldback threshold, the question is: 

    Is there any reliability or lifetime concern with operating the driver in thermal foldback mode indefinitely?  Thanks. 

  • 0
    TI__Genius 16660 points

    A suitable resistor s will  not result in more lifetime problem.

  • 0 in reply to Zhiqian Wu
    TI__Mastermind 32575 points

    Are there any reliability concerns with operating just below the thermal limit of the device with the thermal foldback function disabled?  For example (purely hypothetical to understand how to interpret the specification), how would the lifetime of the device be impacted if we were to operate continuously at 149C (1C lower than the max operating temp)?  Thanks. 

  • 0
    TI__Genius 16660 points

    Hi,

    we can confirm that if the ambient temperature is below 125℃, chips can work normally. And it will not influence the lifetime when the chips work normally. For the junction temperature, it depends on the heat dissipation and is hard to measure. So in some situation, the junction temperature will be higher than 150℃ and leads to shut down. And we can confirm that the chips work normally before shut down.