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UCC15241-Q1: Over-temperature Shutdown

Steve S
Prodigy 50 points
Part Number: UCC15241-Q1
Other Parts Discussed in Thread: UCC14240-Q1

I've done a comparison with the UCC14240-Q1 to see what the main differences were and noticed that the over-temperature shutdown thresholds (e.g. TSHUTPPRIMARY_RISING) have increased from from 150 degC (typ) to 160 degC (typ).  However, the Operating junction temperature range has remainined with a maximum of 150 degC.  Wouldn't this mean that the shutodown would only activate once the device is beyond it's maximum rating (thus not protect the device)?

  • 0
    TI__Expert 7526 points

    Hi Steve,

    Please, notice that the Test Conditions of the TSHUTP in the Datasheet says Tj<140C. Tj can go up to 150C but the Thermal Shutdown at the die (inside the IC) was tested when Tj<140C.

    Thank you

  • 0 in reply to Manuel Alva Hernandez
    Prodigy 50 points

    Hi Manuel,

    Thank you for you reply.  My understanding of the 140 degC threshold is that it is a requirement to be below this junction temperature at power-up in order to allow the device to turn on.  If the device is already powered up, then I wouldn't have thought the 140 degC would apply.

    On the assumption that my understanding is incorrect, can you clarify on how the Thermal Shutdown thresholds are tested when Tj is less than 140 degC?

    Regards,

    Steve

  • 0 in reply to Steve S
    TI__Expert 7526 points

    Hi Steve,

    Thermal Shutdown is tested under many Junction Temperatures Tj (check SOA curves in Datasheet). Load current is increased until it shutdowns (TSHUT_prim_rising=160C). Therefore, peak/maximum power capabilities is tested in the device and reflected in SOA curves. As you can notice, Tj is <140 during this test.

    Thank you

  • 0 in reply to Manuel Alva Hernandez
    Prodigy 50 points

    Hi Manuel,

    That you for explaining the test condition.  The device is powered in an unloaded state whilst the junction temperature Tj is <140 degC.  However, I would expect that the increase in load current would cause Tj to increase above 140 degC as more power is internally dissipated?  Isn't TSHUT_prim_rising a threshold compared against the internally monitored Tj?  If so, then for the IC to reach the TSHUT_prim_rising threshold, then Tj would need to exceed 150 degC (and thus exceed the absolute maximum junction temperature)?

    Regards,

    Steve

  • +1 in reply to Steve S
    TI__Expert 7526 points

    Hi Steve,

    Correct, increasing the load will increase Tj and eventually Tj>150C. SOA curves at very high loads reflect how much power can be delivered by the device pushing up its limits. The condition highlighted in the Datasheet is when first powered up the device (Tj<140C) to be able to test TSHUTP.

    Thank you.