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CSD17579Q5A: How to get the thermal capacity & thermal conductance of MOSFET

user4090349
Intellectual 941 points
Part Number: CSD17579Q5A

Tool/software:

As I want to get the time constant of the MOSFET. I need to get the thermal capacity & thermal conductance.

I think the thermal conductance is the reciprocal of thermal impedance(Probably junction to ambient).

And how to get thermal capacity, from the pulse current capability?

Thanks in advance!

  • 0
    TI__Mastermind 37950 points

    Hello Yun Fang,

    Thanks for your interest in TI FETs. I's not clear to me what you're asking for. TI provides thermal resistance, Rθja and Rθjc in the datasheet. We also include a graph of normalized transient thermal impedance to estimate junction temperature rise for single or repetitive pulses. Do you have an example of the information you are looking for?

    Best Regards,

    John Wallace

    TI FET Applications

  • 0 in reply to John Wallace1
    Intellectual 941 points

    Generally, the temperature rise curve of a conductor follows a Exponential curve. Time constant tau is determined by thermal capacity and thermal conductance. For a MOSFET, thermal conductance is usually known. But the thermal capacity is not so clear. I need this data to drive the temperature rise curve.

  • 0 in reply to user4090349
    TI__Mastermind 37950 points

    Hi Yun Fang,

    Thanks for the update. I am going to see if I can manipulate the data in the ZθJC graph in Figure 1 of the datasheet to generate a plot of heat in joules vs. temperature rise in °C. Please standby. I'll get back to you as soon as I can.

    Thanks,

    John

  • +1 in reply to John Wallace1
    TI__Mastermind 37950 points

    Hi Yun Fang,

    I pulled up the characterization data collected during product development which includes Zθjc used to generate the normalized transient thermal in Figure 1 of the datasheet. Using this data, I generated a single pulse curve as shown below. I assumed 1W power pulse and multiplied it by pulse width to get energy. For the temperature rise, I used: ΔTj = P x Rθjc x Zθjc. Does this make sense to you?

    Thanks,

    John