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LTC3729 model does not discharge RUN/SS cap

Category: Software
Product Number: LTC3729
Software Version: 17.1.10

The LTC3729 datasheet states that the if the output voltage falls below 70% then the RUN/SS pin will start discharge the softstart cap.  I do not see this occur in the model when I apply a heavy step load to the output.  The Run/SS pin never discharges even though I'm in a current limit and voltage has folded back well below 70%.  I'm trying to better understand how this behaves to balance softstart time vs not latching off, but the model does not appear to work properly.


  • Hi jer1,


    I will reach out to the owners of this ADI part LTC3729. They will be the ones to facilitate the checking and correction of the LTspice model.

    Please be advised that this process may take time depending on the prioritization.

  • Hello,

    I have confirmed that the RUN/SS pin in the LTC3729 LTspice model does not work correctly in regards to the over-current latch-off. The RUN/SS pin of the actual LTC3729 circuit does work as described in the data sheet. If the supply requires over-current latch-off, then the LTC3729 will provide this function. If not required, then over-ride the RUN/SS pin with a 5uA pullup as described in the data sheet.  

    Note, regardless of which method is used, drive the RUN//SS pin with an external UVLO comparator or logic to reset it when Vin goes  low. This is shown below.

    Best regards,