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TPSM831D31EVM: Setting up Vout

Part Number: TPSM831D31EVM

Hi Team,

Good afternoon, my customer is evaluating the TPSM831D31EVM for use in their design and has a couple questions:

Is it possible to set up the board so that it comes up with pre-set voltages and with the outputs enabled? That is can it be made to work like a conventional regulator. I’m sure the answer is yes but are there any tips to help achieve this.

I have been experimenting with the GUI and writing to NVRam and using all the buttons but the card does not seem to remember the settings through a power-cycle.

There is also a slightly difficult aspect to the GUI in that the “Vout Command” box it too small to read. How is this adjusted? I have to use a high magnification headset.



  • HI John,

    For quick discussion, I will contact you by email.

  • Hi John,

    1. Turn on the board after power on.

    The module is set in “CONTROL  pin only, logic high” in factory default.

    A_EN and B_EN pin are pulled high to 3.3V on EVM when Vin power is applied. However, when PMBus USB adaptor is connected to the board, these two pins are pulled low by USB adaptor. You need to go to “System Monitor” to pull the pins high manually. I will work with our GUI team to make it more user friendly.

    If the USB adaptor is disconnected from the board, A_EN and B_EN pins will be pulled up on EVM and turn on the rails.

    2. Set up boot voltage

    In Configure->Static tap, set both “Vout command” and “VBOOT” to the new value, store configure to NVM. That will make the module start up to the new Vout value after power on.



  • Thank you, yes setting "VBOOT" and writing to NVRam is the key to changing the voltage in a non-volatile way.

    Still have a problem with the enable feature. Device always comes up with output off until I toggle the Operation field in the On-Off Config column by clicking it using the GUI.

    I want to power the device and for it to immediately start converting without any GUI instructions.

    Any help appreciated.



  • I have spent another hour or so but not found the secret combination that will allow the device to turn-on immediately on power-up.

    Any assistance much appreciated.


  • Hi Phil,

    Sorry to hear it took you a lot of time with issue unsolved.

    The ON_OFF_CONFIG is set at "control pin only and logic high" in factory default, if A_EN and B_EN pin voltage is high, the part will turn on instantly after power on.

    If ON_OFF_CONFIG is changed to "operation only", user needs to click "ON" in operation field to turn on the part after every power on. This is a PMBus standard. I believe this is the issue you have right now.

    1. Change ON_OFF_CONFIG to "control pin only and logic high"
    2. If TI USB dongle is not connected to EVM, the part should start up after power on, because A_EN and B_EN pins are tied to 3.3V on EVM.
    3. If TI USB dongle is connected to EVM, go to "system monitor" and make sure the control line is set high all the time. The screen shot of "system monitor" is provided in my previous reply.

  • Thank you Qian, yes that works.

    I added steps of "write to hardware" and "write to NVRAM" then I pulled the plug on the Fusion interface.

    Don't know if these additional steps are needed.

    Didn't work immediately but when I removed the jumpers, already fitted on the board, it worked nicely.

    Thanks for helping me find this combination. I wanted to see this work before proceeding with development..


  • Hi Phil,

    Glad the issiue is solved.
    To change ON_OFF_CONFIG, "write to hardware" and "write to NVRAM" are needed to make the new setting effective and store the new setting in NVM.