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TPS53647: Setting output with writing VOUT_COMMAND register

Muhammet Alçın
Prodigy 10 points
Part Number: TPS53647

Tool/software:

Hello, we are using TI’s TPS53647 with pin strap configuration. The power IC powers up according to the strapped value and starts driving the PWM (VOUT). After that, we want to change VOUT by writing a VID value into the VOUT_COMMAND register, but it doesn’t work. The VOUT_MAX register is still at its default (FF). Later, we tried writing the VID value into the MRF_specific_11 register, and in this case, the IC actually drove VOUT according to the written value. However, it ignored the VOUT_MAX limit and exceeded it.

Why is this happening? Why can’t I change the output voltage using the VOUT_COMMAND register?

  • 0
    TI__Expert 4235 points

    Hi,

    Could you provide the project configuration file (.xml), exported using TI's Fusion Digital Power Designer?

    What were the values written to VOUT_COMMAND and MFR_SPECIFIC_11?

    Regards,

    Troy

  • 0 in reply to Troy Johnson
    Prodigy 10 points

    Hello Troy,

    Thank you for your response. Let me explain the steps I followed:

    • First, I set VOUT_MAX to 1.200 V. I verified this with the oscilloscope, and the value was correct. Then, I measured the output voltage at the power stage (driven by PWM) with a voltmeter, and I observed 1.030 V, as shown in the screenshots below.

    • Next, I set VOUT_COMMAND to 0.94 V. Again, I checked with the oscilloscope and the voltmeter, but the output voltage still showed 1.030 V without any change.

    • Then, I set the VBOOT value to 1.5 V, and I observed the output voltage correctly as 1.507 V, also confirmed by the screenshots below.

    • Finally, I set VBOOT to 1.300 V, and the output voltage was correctly measured as 1.306 V.

    In summary, the values written to VOUT_COMMAND do not affect the output voltage, while writing to the MFR_SPECIFIC_11 register directly sets the output voltage — even if it exceeds the VOUT_MAX limit.

    As requested, I am also attaching the XML file exported from Fusion Digital Power Designer.

    Best regards,
    Muhammet

    https://drive.google.com/file/d/1MGO7_96bPk8VuOCOSz2uqJoD0cv9wnPk/view?usp=sharing

  • 0 in reply to Muhammet Alçın
    TI__Expert 4235 points

    Hi Muhammet,

    Are you able to directly attach the exported .xml file to this post, instead of pasting the text from the file? You should be able to do this when adding your reply by selecting Insert -> File. I attempted pasting the text you provided into my own file, but was not able to open the file in Fusion. 

    When you are writing these values through Fusion GUI, are you only selecting "Write to Hardware" or are you also selecting "Store to NVM"? If storing to NVM, STORE_DEFAULT_ALL command will cause VOUT_COMMAND to return to VBOOT value, and VOUT_MAX to return to 0x00FF.

    Regards,

    Troy

  • 0 in reply to Troy Johnson
    Prodigy 10 points

    Hi Troy,

    Thank you for your reply. Here is the Drive link to the exported .xml file: [https://drive.google.com/file/d/1MGO7_96bPk8VuOCOSz2uqJoD0cv9wnPk/view?usp=sharing].

    Regarding your question, I am only selecting "Write to Hardware". I am not selecting "Store to NVM". Also, when I read back through the FPGA, I can confirm that the correct values are indeed being written to the VOUT_COMMAND register.

    Best regards,
    Muhammet

  • 0 in reply to Muhammet Alçın
    TI__Expert 4235 points

    Hi Muhammet,

    I cannot open and download files from drive links. If you cannot attach the .xml file to this post, you can send it to me via email: 

    I will continue looking into what could be causing this issue, and I will update you by the end of this week (9/5).

    Regards,

    Troy

  • 0 in reply to Troy Johnson
    Prodigy 10 points

    Hi Troy,

    I’ve sent this message via email — I hope you’re able to open it without any issues and import it into Fusion Digital Power Designer successfully.

    Best regards,
    Muhammet

  • 0 in reply to Muhammet Alçın
    TI__Expert 4235 points

    Hi Muhammet,

    Thanks for sending .xml file, I was able to open in Fusion and import to TPS53647 device on EVM.

    While testing on EVM with provided config, I have not been able to replicate the behavior you are seeing. Writes to VOUT_COMMAND change the output voltage appropriately. Attempting to set VOUT_COMMAND or VBOOT above VOUT_MAX will result in output voltage instead being set to VOUT_MAX, and VOUT_MAX Warn being tripped.

    Can you share your schematic file so I can compare to EVM? If you cannot attach here, you may send it to me through email as with the .xml file.

    Regards,

    Troy