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TINA/Spice/LMZM33603: Unable to get -5V output with 28V input. I tried to simulate with TI's example inverting design.

Vinayak Chabbi
Expert 1100 points
Part Number: LMZM33603
Other Parts Discussed in Thread: TINA-TI,

Tool/software: TINA-TI or Spice Models

Hi,

I'm looking for a simulation of LMZM33603, input +28V and I want -5V output. 

I tried TI's example, but couldn't get the -5V. 

Please help.

Thanks,

Vinayak

  • 0
    TI__Intellectual 1090 points

    Hi Vinayak,

    The model on Web works fine for Vin=28V, Vout=-5V. I am using a load current of 3A. I have attached the obtained results for your reference.

    Could you please recheck?

    If the problem persists, zip the project and forward it so that we can have a look. 

    Regards,

    Karthik

  • 0 in reply to Karthik Kulkarni
    Expert 1100 points

    Hi,

    PFA.

    I'm trying to simulate it on TINA.

    LMZM33603_N5V.rar

    Thanks,

    Vinayak

  • 0 in reply to Vinayak Chabbi
    TI__Intellectual 1090 points

    Hi Vinayak,

    PFA the updated .TSC file.

    LMZM33603_N5V_modified.TSC

    The following modifications were done:

    1. The macro file was modified slightly as the earlier model on Webench did not support IBB.

    2. All the GND pins(PGND, AGND etc.) need to be connected to Inverting output(-5V in your case).

    3. The feedforward capacitor(C4) was too high. I have changed it to 100pF.

    4. The feedback resistor(R4) was not in accordance to a VOUT of 5V.

    5. Modified analysis parameters to avoid non-convergence.

    There is a spike in VOUT at the start of sim due to a capacitor connected between VIN and VOUT(C2). Connect it to ground(0V) if you want to avoid that.

    Regards,

    Karthik