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TPS23753: Good choice for high temperature application?

Benjamin Bawkon
Expert 1065 points
Part Number: TPS23753
Other Parts Discussed in Thread: PMP9175, , PMP20220, TPS23751

Hello,

I have a need for a POE PD design that will power a remote sensor.  This sensor could frequently operate in environments around 85C, and even be subjected to excursions of 110C or so.

Power requirements are 5V with typical current being 100mA and short term maximums of 1A (50-100mS at these levels, infrequently).

I've found PMP9175 to be a good starting point for the design.  Would you agree?  I plan to replace the majority of external components with 125+C rated equivalents.

Does PMP9175 and TPS23753 make the most sense for a high temperature design?  The ultimate goal is to be able to function at the highest temperatures possible, so if another PD controller makes more sense, I'm very open to suggestions.  PMP9175 was selected as a starting point purely because the voltage/current output suited our requirements.  This application is such that sacrificing life-span of the device is acceptable in order to function at extreme temperatures.  Our end users would be truly delighted if we could function at 125C ambient, and would happily accept <1000 hour lifespans as a tradeoff.

Thank You,

Ben

  • 0
    Expert 1065 points

    One additional question - It would seem beneficial to me to replace the mosfets on PMP9175 with much lower RDSon parts that also have better heat dissipation characteristics. The tradeoff for lower RDSon is primarily higher Qg. What would TI recommend as the upper end for acceptable Qg on these two parts?

  • 0 in reply to Benjamin Bawkon
    TI__Genius 9230 points

    Hi Benjamin,

    To summarize your two questions:

    1. Which PD designs have the best thermal performance?
    Generally speaking, any PD controller with an exposed heatsink at the bottom will do a better job of heat dissipation. They would have HTSSOP, VQFN, or PowerPAD packages. Based on your chosen design, I would recommend PMP20220. A 5V/3A design that uses TPS23751.

    2. What is the highest acceptable Qg for said PD+PWM controllers?
    According to section 2.7.1 of SLVA305C, a gate charge under 20nC is recommended. In section 8.2.2.11 of the TPS23751 datasheet, it describes how the gate charge of the chosen MOSFET is taken in to consideration when sizing the Cvc capacitor connected to the Vc supply pin. A higher gate charge would require a larger Cvc capacitor.


    Thanks,
    Tom