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TPS7H1101A-SP: Availability of Model to Simulate Frequency Response

Part Number: TPS7H1101A-SP
Other Parts Discussed in Thread: TPS50601A-SP

Is there a TINA TI or PSPICE model available that we can use to simulate the frequency response of this LDO? Goal is to generate a BODE plot to evaluate stability with out selected CIN, COUT, and CCOMP.

If we are able to simulate or measure the frequency response, should we target a phase margin ~60 degrees similar to TPS50601A-SP. This ensures that we should have adequate phase margin over the full operating temperature range.

  • Joshua,

    The WCA model is best suited for stability simulation.

    This model can be found in the product folder: https://www.ti.com/lit/zip/slvmda6

    If this answers your question, please click "This Resolved My Issue"
    Regards,
    Wade

  • The schematic in the reference design says "Please reference the WCA Model User Guide for additional information."

    Unfortunately, I haven't been able to find this document. Can you provide it?

    Alternatively, can you describe which signals to probe to generate a Bode plot?

  • Joshua,

    Thanks for pointing out that the UG is missing.   I suspect this happened when the modelling team performed modifications to the source files to be uploaded for Pspice for TI.

    I am attaching the last published version here.   

    I will follow up with the team to get this published again.

    For the Bode plots, the easiest way with Pspice, to to select "add trace", then Function or Macros drop-down to "Plot Window Templates", then select one of the Bode Plot templates, and use V(VOUT) for the argument.

    slvubt7.pdf

    Regards,

    Wade

  • Thanks for the help, Wade!

    Quick follow up:

    • Do you think targeting 60 degrees of phase margin is still the best strategy?
    • What should the cross over frequency be?
  • Joshua, I am out of the office today.  
    I will respond back on Monday.  
    I want to check with some coworkers to get their feedback on crossover.  
    Have a great weekend.  
    Regards,

    Wade

  • Joshua,

    I believe different companies and/or industries have their own goals for stability requirements.  This may also be a function of the system requirements.

    One comment though, is that LDOs will typically not have the same amount of aging contribution as a switching regulator may have due to fewer components subjected to the aging.  This could allow for somewhat lower PM requirements for an LDO vs a switching converter with an inductor.

    The cross over frequency can vary a fair amount based on load and capacitance.   The crossover frequencies of the baseline schematic in the WCA project and across load in the WCA model ranges from no load cross over of 20kHz to a full load cross over greater than 200kHz.   Varying output capacitance and compensation will also influence this range.   In the testing of this model, the largest crossover frequency documented was just under 240kHz.

    If this answers your question, please click "This Resolved My Issue"
    Regards,
    Wade