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TINA/Spice/CSD87355Q5D: MOSFET Power Loss Calculator vs. SPICE

Reto Christen
Prodigy 80 points
Part Number: CSD87355Q5D
Other Parts Discussed in Thread: TINA-TI,

Tool/software: TINA-TI or Spice Models

Hi,

for a project I am trying to calculate switching losses in MOSFETs for different currents and frequencies. 

As a test object I have chosen the part CSD87355Q5D. My first goal was to analytically calculate (http://www.ti.com/lit/an/slpa009a/slpa009a.pdfthe losses and compare them with the results given from the online tool "MOSFET Power Loss Calculator". This works fine.

Afterwards I wanted to build the same model in SPICE to compare the results to the calculated results (it is not really necessary, however, it's always good to cross-check). Unfortunately, the simulated losses do not correspond with the calculated losses.

Comparison:

MOSFET Power Loss Calculator:

SPICE Model (loss results from dissipated power W):

Does anyone has a clue if I am doing something wrong or is the SPICE Model not working properly?

Since I am rather new to this field, it might also be a strange question. Maybe it is simply not possible to do it like this? 

Anyway, I would be happy about any help. 

Thanks,

Reto

  • 0
    TI__Mastermind 18200 points
    Reto,
    I am looking into this for you. To confirm - your manually calculated losses mostly agreed with the online calculator, correct? It was just the spice model simulation that did not correspond and looks like came in much lower.
  • 0 in reply to Brett Barr1
    TI__Mastermind 18200 points
    Reto,
    Our apps team advises against using SPICE models for power loss estimations. The SPICE model isn't designed for this purpose, and a lot of the parameters are not calibrated to match the real values for Ploss.

    Assuming your manual calculations and the online calculator were in decent agreement, I would trust those losses more. And since they are higher, it will force you to be more conservative in your design.
  • 0 in reply to Brett Barr1
    Prodigy 80 points

    Brett, 

    Thank you very much for this fast answer. 

    Yes, my manual calculations and the results from the online calculator are in agreement. As you suggested, I will take these calculations for further designing.

    Once again, thank you very much. I highly appreciate this.

    Reto