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THVD1550: Behavior in the event of a permanent short circuit on these outputs to the ground (0V) ?

Yvan KERJOUAN
Prodigy 10 points
Part Number: THVD1550

Hello everybody.

I need to justify a requirement concerning its permanent behavior in the event of a short circuit of its outputs to 0V.

For me, this component limits its current to +/-250mA. it is powered by 5,3V.

This means that it will definitely heat up and burn because it has no thermal protection.

Correct ?

(5.3V x 0.25A) = 1.3W

The ambient temperature of my PCB must be +85°C and i use SOIC Package for this component.

  • +1
    TI__Guru 56640 points

    Hi Yvan,

    In a short and easy answer, yes you could calculate the worst case power dissipation in this way. The device itself does have a thermal shutdown but it's at 170C and is mainly meant for fast transient protection. In practice, the device itself would probably limit its current earlier than 250mA and as it heats up the Ron of the CMOS outputs would increase and the Vth of the device would also increase resulting in the clamping current to get lower as it heated up. Using your method would be the most practical/easiest way of calculating power though.

    Thermal metrics are also something that can vary with PCB design so the datasheet values reference an industry standard. In practice your set up may be more thermal efficient. Using your power calculation and the SOIC package, the device would hit an estimated junction temp of ~230C though the device should hit thermal shut down at 170C. To keep the device within 150C junction the max power allowed would be ~578mW (assuming 85C ambient).

    -Bobby

  • +1
    Prodigy 10 points

    Hi Bobby,

    Thank you very much for your analysis and this quick feedback !

    Regards,
    Yvan