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TPS650941EVM-116: Buck 3 not changing output voltage

Aaron Mears
Prodigy 20 points
Part Number: TPS650941EVM-116
Other Parts Discussed in Thread: IPG-UI, TPS65094

I'm testing some functions of this evaluation module and having a problem with one function. Using IPG-UI with the package installed for this part, I can change bits and read/write without any issues. I have manipulated the buck controllers and LDOs, and tested some of the enable/disable features. All have been successful except BUCK3_VID (7 non-reserved bits for setting the DC output voltage). On any other buck, I'll make a change, write it, and it will be reflected on the hardware. But for whatever reason, BUCK3 is stuck at the default 1.05V and won't change. I have verified via the "read" function that the bits have been modified, but the output is still the default.

The BUCK3_DISABLEB bit functions as it should, enabling or disabling the output. But no matter what I write to BUCK3_VID, the output voltage is unchanged. It does write, and when I read, it reflects the correct bits that I wrote. I have attempted it with and without a load.

Looking at the schematic, the only significant difference I see between BUCK4/5 and BUCK3 is that 4/5 have a pull-up resistor on the output to BUCKX_1P8, which is not present in the schematic for BUCK3. Any ideas what I could be missing?

  • 0
    TI__Expert 6700 points

    Hello Aaron,

    We have assigned this ticket to the appropriate engineer and he should be getting back with you in the next day or so. Thank you.

    Regards,

    Alex

  • 0 in reply to Alex Saenz
    Prodigy 20 points

    Hi Alex,

    Thank you. Have you heard any word from this engineer? I just want to make sure this thread has not been forgotten.

    -Aaron

  • 0 in reply to Aaron Mears
    TI__Mastermind 19405 points

    Hi Aaron,

    This E2E was accidentally assigned to another engineer and it was re-assigned today. We apologize for the inconvenience and delayed response. I will review your information and provide an update within the next 24Hrs.

    Thanks,

    Brenda

  • 0 in reply to Brenda Diaz
    TI__Mastermind 19405 points

    Hi Aaron,

    I have successfully changed the output voltage on Buck3 using BOOSTXL-TPS650861 which is the customer programming BoosterPack for the variant that comes with two "blank" OTP memory (TPS65086100). I have also placed an order for a TPS65094 EVM (TPS650941EVM-116) that should arrive early next week. Could you please provide the details of your setup (EVM jumper config and the steps followed to change the voltage on Buck3) so I can replicate the issue on my end?

    In the meantime, could you please specify the configuration of each of the control signals on the S1 switch?

    Thanks,

    Brenda

  • 0 in reply to Brenda Diaz
    Prodigy 20 points

    Hi Brenda,

    Thanks for your response. All 6 control switches in the "off" position (i.e. not tied to ground), 13V on the VSYS screw terminals, DMM measuring across the BUCK3 test points. Using the IP-GUI, I start by reading all the addresses. BUCK3CTRL, which is located at address 0x22, has 1 bit which cannot be modified and the other 7 bits "sets the buck 3 nominal regulator operating voltage". By default, on the first read, they contain b0010001 (h11), representing 1.05V on the output. I change the bits to b0000101 (h05), for example, which should change the output to 0.75V, and write. I measure at the output with the DMM, but the output remains 1.05V. I read the 0x22 address, and it returns b0000101 (h05) as it should, but the output voltage is still the default (1.05V). Every other buck controller/convert functions as expected.

    Kind regards,

    Aaron

  • 0 in reply to Aaron Mears
    TI__Mastermind 19405 points

    Hi Aaron,

    Thanks for providing the information! I will get back with an update early next week (by Tuesday Feb-15-2022). 

    Thanks,

    Brenda

  • 0 in reply to Brenda Diaz
    TI__Mastermind 19405 points

    Hi Aaron,

    Just wanted to provide an update on this. The TPS65094 EVM hasn't arrive yet (it should arrive sometime this week) but I reviewed the GUI files in details and identified a register address that is probably not up to date in the version that is available in the product folder. This could explain why you are not able to make changes to Buck3_VID specifically. Once the EVM arrives, I will test it with the GUI available in ti.com as well as the internal version to confirm my hypothesis.  

    Thanks,

    Brenda

  • 0 in reply to Brenda Diaz
    Prodigy 20 points

    Thanks for the update Brenda, please continue to keep me posted as things develop.

    Kind regards,

    Aaron

  • 0 in reply to Aaron Mears
    TI__Mastermind 19405 points

    Hi Aaron,

    Yes, I'll let you know about the results as soon as the EVM is received. 

    Thanks,

    Brenda

  • 0 in reply to Brenda Diaz
    TI__Mastermind 19405 points

    Hi Aaron,

    I have confirmed the GUI files that are linked to the EVM user's guide are not the latest and the Buck3 register address is not up to date. The GUI version you have shows 0x22 and it should be 0x23. This has been validated. I'm working with the team internally to update the source files so you can re-download the GUI. If we are not able to update the source files within the next 3 business days, I'll send you a private E2E message with a file extension ".json" that you can easily replace to fix the issue. 

    Thanks,

    Brenda

  • 0 in reply to Aaron Mears
    TI__Genius 11020 points

    Hi Aaron,

    Note that due to public holiday in US today your answer might get delayed to Tuesday.

    Thanks.

    Regards,

    Tomi Koskela

  • 0 in reply to Brenda Diaz
    Prodigy 20 points

    Hi Brenda,

    Any luck with the update so far? I haven't heard anything one way or the other.

    Kind regards,

    Aaron

  • 0 in reply to Aaron Mears
    TI__Mastermind 19405 points

    Hi Aaron,

    I apologize for the delay on this. An E2E request has just been sent. Please let me know if it was received on your end to see if it enables the message option so I can send the updated .json file. 

    Thanks,

    Brenda

  • +1 in reply to Brenda Diaz
    TI__Mastermind 19405 points

    Hi Aaron,

    Thanks for accepting the request! I have sent a direct message with the updated file. Could you please follow the instructions sent in the private E2E message and let me know if you are able to change the output voltage on Buck3?

    Thanks,

    Brenda

  • 0 in reply to Brenda Diaz
    Prodigy 20 points

    Hi Brenda,

    Changed out the .json with the updated one and it works just like it's supposed to! Thanks for all your help!

    Kind regards,

    Aaron