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UCC21710: Estimating MOSFET die temperature

Ian Paull
Prodigy 20 points
Part Number: UCC21710


I would like to estimate MOSFET die temperature from measured Vds_on and presumed Rds_on from data sheet values. Is there an easy way to derive Vds_on from the protection signal I already develop on the OC pin of the UCC21710QDWQ1 (per the data sheet schematic) and then send it into the Ain pin to go across the isolation barrier? If it is possible, do you think it is practical?

Thanks.

Ian

  • TI__Genius 10652 points

    Ian,

    I understand your idea here.

    I have seen there are publications about this real time TJ estimation to achieve some kind of closed loop about it.

    Its quite intense and i wouldn't say its ready for production. I think in the future it will be.

    Ican not comment on how accurate this would be other than pointing you to others researchers works,  but my guess would be "not very" without significant work on your end for thermal modeling/calibration because the FET mfr can't or wont provide all of the data needed, and of course youd then have to implementing this all in the controller.

    From feasibility standpoint, you can technically do what you are asking, even using AIN, but i think its still infeasible and not practical.

    * In normal use case, you already have set the max ambient or case temperature, and the whole design is already designed around keeping the FETs/ICs below their TJ rating. So, the reasons you would have over temperature even is as follows.

    * You will get overtemp from Short-circuit events -> OC gives protection against this

    * You could get overtemp from another failure system, or maybe the system is being used in a volcano. In that case I would recommend NTC diode/thermistor to accurately to detect Overtemp condition.

    I would recommend to use thermistor or even FET module which has built in thermal diode or thermistor, which is robust and accurate.

    If this answers your question, please let me know by pressing the green button. Please let me know if you have any more questions.

    Best

    Dimitri