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UCC21542: Design UCC21542 and simulation

Ethan Ku
Prodigy 90 points
Part Number: UCC21542
Other Parts Discussed in Thread: UCC21550

Tool/software:

i am designing a circuit using the UCC21542 isolated gate driver in our project and have some quesion that need to be comfirmed 

1.Can UCC21542 drive two MOS(C3M0045065D by Wolfspeed) as depicted in schematic 

2.we attempted to simulate the UCC21542 using Pspice for TI,based on Figure 10.3 form datasheet , but it does not work.

How can we implement a negative voltage for turning off the MOSFET in PSpice for TI?

3.I found that the OUTA voltage level seems to follow V7 (isovolt)? Could you confirm this behavior?

  • 0
    TI__Intellectual 1925 points

    Hi Ethan,

    Firstly, I would make sure that your -3V VSS is going to be the standard ground voltage for everything pertaining to the output stage. By the looks of things, you have a 400V source, which assumes a +400V and 0V on each terminal. This effectively will set the ground voltage to a zero for everything tied to it. Now for your -3V source, it only has a 0.001Ω resistor between it and another ground connection. I want to make sure this is not going to result in exceedingly high current through that resistor. Here is an image with some notes on it for further clarification:

    To answer some of your questions directly:

    1. The UCC21542 will be able to drive your stated configuration, as long as the VSS/ground issue mentioned above is sorted out. The part can support VDD-VSS voltages of up to 20V, and your configuration of 15V - (-3V) = 18V falls into this specification, the driver will be able to support this application.

    2. In PSpice, if it does not allow you to assign a negative voltage value to a source, my first recommendation would be to try to assign a 3V value to it, and then reverse the connections (connect the + side to 0V GND).

    3. The OUTA pin should not be reading 1500V, as it should be tied to either VDDA or VSSA based on INA. I would first recommend to see my initial recommendations for your schematic, and if the issue still persists, please let me know so I can look into the PSpice model.

    Best regards,

    Will

  • 0 in reply to Will Appelt
    Prodigy 90 points
    Hi Will
    Thanks your supporting 

    I have followed your recommendation

    1.to reverse the connections

    2.re-simulate in order to modify the isoVoltage.

    3.add resistor between -3V to MOS Source

     however,the issue still exits and The isoVoltage is affecting the OUTA output level. I have attached my file for your review.

    UCC21540_C3M0045065D.DSN

    Could you please help me check it?

    thank you in advance 

  • 0 in reply to Ethan Ku
    TI__Mastermind 23206 points

    Hi Ethan,

    You should use a differential voltage meter for measuring voltages on the isolated side, to avoid including the common-mode voltage (here 100V) in the measurement.

    ucc21550-q1-2024-07-02T18-01.zip

    You can use the attached UCC21550 simulation file for an example. There is no ground reference on the isolated side, and the outputs are measured differentially.

    Best regards,

    Sean

  • 0 in reply to Sean Cashin
    Prodigy 90 points

    HI Sean

    thank your feedback

    however .  i use UCC21550 to drive a NMOS for testing , I cannot observe the MOS switching 

    could you help me test it ?

    thnaks 

  • 0 in reply to Ethan Ku
    TI__Intellectual 1925 points

    Hey Ethan,

    It appears that the gate driver is outputting the correct 12V that it should on the A channel. If your NMOS is not switching properly, I would double check it's parameters to make sure that your setup is reaching the proper threshold to turn it on/off.

    Best regards,

    Will

  • 0 in reply to Will Appelt
    Prodigy 90 points

    hi Will

    could you help me check this issue ? i have tried it several times but NMOS still does not work 

    thnaks 

  • 0 in reply to Ethan Ku
    TI__Intellectual 1925 points

    Hi Ethan,

    Kindly review the NMOS parameters and power supply configuration, as well as the UVLO setting for UCC21550. If you have selected a higher UVLO option for UCC21550, then the 12V on VDD will likely not turn it on.

    Best regards,

    Will

  • 0 in reply to Will Appelt
    Prodigy 90 points

    Hi Will 

    what is your meaning of the  "UVLO setting for UCC21550"? 

    can Pspice model UCC21550 set UVLO?

  • 0 in reply to Ethan Ku
    TI__Intellectual 1925 points

    Hi Ethan,

    UCC21550 has multiple different UVLO options listed on the datasheet. If I remember correctly, the PSpice model should be the 12V UVLO option, which is fine in your case. Your waveforms shown earlier indicate that the gate driver is in fact switching on, even though the MOSFET is not. I recommend to take another look at the MOSFET parameters and configuration to determine why it is not switching.

    Best regards,

    Will