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CSD19536KCS SOA and simulation

Zhongxu Qiu
Prodigy 20 points
Other Parts Discussed in Thread: CSD19536KCS

Hello,

i want to use the mosfet CSD19536KCS for a motor system. When i read the datasheet i find some questions.

Figure 7: if Tc=125°C, Id=100A, then Rds(on)=4mohm

Now Vds=100A*4mohm=0.4V

Figrure 10 (SOA): when Vds=0.4V, Id=65A<100A.

Figure 12: when Tc<125°C, the max. Id=150A.

These figures dont match togehter. Is there something wrong with the SOA or the resistance Rds?

And i try to simulate this model using LTspice. In the Pspice model library there are only 4 nodes. I think it should be 5: Gate Source Drain Tj Tc.

So anbody can tell me how to solve it? Kindly explain.

 

best regards,

Qiu

 

 

  • 0
    TI__Mastermind 18200 points
    Qiu,
    The resistance limitation in the SOA assumes worst case scenario, so the FET is considered to be operating at its max temperature of 175deg.

    Max resistance of the FET is 2.7mOhm, and temperature coefficient at 175 deg is around 2.2, so worst case resistance of the FET is actually closer to 6mOhm in this scenario.

    Thus at .4Vds, we can predict Id = V/R = .4/.006 = 67A. This agrees with FIgure 10 so there is no contradiction there.

    Figure 12 is just a thermal calculation base on RthJC, max temp of the FET = 175, and the max resistance of the FET at this temperature of 6mOhm. It is clipped at 150A because that is the max current this package can handle, independent of thermal conditions. I do not believe there is any contradiction here either.

    I will inquire as to the nodes in the spice model, but I assume two of these can be combined. I will have to get back to you.
  • 0 in reply to Brett Barr1
    TI__Mastermind 18200 points
    Here is the response I got from our Spice model author.

    It is a 5 terminal model as following:

    *********************************************
    * 1=d 2=g 3=s 4=TA/TC 5=TJ
    * set the voltage of terminal 4 equal to
    * the numeric value of ambient and/or case temperature
    * Terminal 5 is for sensing only, V(5)=junction temperature numerically
    *********************************************
  • 0 in reply to Brett Barr1
    Prodigy 20 points
    Hi,

    Thank you for your answer. Now I want to simulate this model using LTspice. It seems that, it requires a unencrypted model. (I dont want to use TINA TI Spice, the worse is that model in TINA TI is also 3 Pins without the thermical pins, the Pspice model doesnt work in LTspice.) Could you send me the general model, that can in LTspice work. Thank you very much.

    with best regards
    Qiu
  • 0 in reply to Zhongxu Qiu
    TI__Mastermind 18200 points

    Qiu, 

    Unfortunately, as a semiconductor manufacture, we are not allowed to provide LT Spice Models, and we can only provide unencrypted PSpice models to customers with and NDA.