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TMDXEVM8148: Some queries regarding power sequencing in DM8148 evaluation board.

Jagdish Karamchandani
Expert 1420 points

Part Number: TMDXEVM8148

Hi TI support,

1. In DM8148 datasheet it is written that 1.8V supplies should be brought up before 3.3V, however in DM8148 evaluation board schematic from Mistral I found TPS_VDDA_1V8 is generated from TPS_BCK2_3V3 which is 3.3V rail. So there seems violation of power sequencing. Can anybody explain why?

2. Since TPS65232A2 is not recommended for new designs & we are not using PCIe feature can we eliminate this IC with below implementation,

=> We are having +24V rail so generate +5V from 24V rail & use 5V power good signal to enable separate 3.3V regulator. Again this 3.3V regulator will have input from 24V.

Awaiting your response.

Regards,

jagdish

  • 0
    TI__Guru**** 170625 points

    Hi Jagdish,

    Jagdish Karamchandani said:
    1. In DM8148 datasheet it is written that 1.8V supplies should be brought up before 3.3V, however in DM8148 evaluation board schematic from Mistral I found TPS_VDDA_1V8 is generated from TPS_BCK2_3V3 which is 3.3V rail. So there seems violation of power sequencing. Can anybody explain why?

    DM814x latest datasheet is correct and with highest priority. EVM was designed based on old version of the DM814x datasheet, that is the reason of misalignment.

    Jagdish Karamchandani said:

    2. Since TPS65232A2 is not recommended for new designs & we are not using PCIe feature can we eliminate this IC with below implementation,

    => We are having +24V rail so generate +5V from 24V rail & use 5V power good signal to enable separate 3.3V regulator. Again this 3.3V regulator will have input from 24V.

    This depends on the requirements of the specific PMIC chip that you will use to power supply DM814x device (on EVM this is TPS659113). You should check in the PMIC forum (link below) regarding the specific requirements of this PMIC, if supplying it with 5V first, then 3.3V is fine. This is out of scope of the DM814x device.

    Regards,
    Pavel

  • 0 in reply to Pavel Botev
    Expert 1420 points
    Hi Pavel,

    I shall move TPS65232 query to pertaining forum but just further query that assuming we are to use same TPS659113 can we ensure correct sequence by powering VIO section of TPS659113 from 5V (TPS_EVM_5V0) instead of 3.3V (TPS_BCK2_3V3)?

    Regards,
    jagdish
  • 0 in reply to Jagdish Karamchandani
    TI__Guru**** 170625 points
    Jagdish,

    From what I understand, your question is regarding TPS65x PMIC, not regarding DM814x device. I would suggest you to check into TPS65x PMIC documentation and ask/post into PMIC forum.

    Regards,
    Pavel
  • 0 in reply to Pavel Botev
    Expert 1420 points
    Pavel,

    It is unfortunate that client is rolled like ball. One query asked yesterday on PMIC forum was suggested to check on Webench that you told me to ask on PMIC forum. If everything we have to do by going in so detail it will take lot time then what is use of TI support. What type of support do TI provide in EVM? For every minor design related question do we ask Mistral who works on professional basis? If TI is selling the board, TI should allocate some resource who could look into EVM design. I understand business & engagement of TI & Mistral but that could be where customer engages Mistral for complete solution. If client wants to work by his way, why TI is not helping?

    TI Indian top heads assured me of support on forum, I never knew we will be supported in this way. If we were not be supported then things should have been conveyed very clearly that you wouldn't get any design related support from TI & TI should write in bold letters on EVM website so each customer understands well before buying the board. Remember, error only happens once that seems is done by selecting DM8148 & never again for other projects.

    Thanks,
    jagdish
  • 0 in reply to Jagdish Karamchandani
    TI__Guru**** 170625 points

    Jagdish,

    DM814x is very old device and support is very limited, refer to the below e2e post:

    e2e.ti.com/.../426680

    And your question is not related neither DM814x device nor DM814x TI EVM, but to your custom design.

    Regards,
    Pavel

  • 0 in reply to Pavel Botev
    Expert 1420 points
    Pavel,

    The posts that you show me is very clear about no support for EVM to clients which was not conveyed to me in email communications with TI people. This is very lamenting.

    "And your question is not related neither DM814x device nor DM814x TI EVM, but to your custom design."

    DM8148 can't exist independently in board & certainly questions will come about design & interface with DM8148 like any other TI chips. Every customer buying DM8148 will have its own design. I understand it is custom design & I never asked any design help but just clarification/guidance on power sequencing to help me in design. Anyway thanks,

    Jagdish
  • 0 in reply to Jagdish Karamchandani
    TI__Guru**** 170625 points

    Jagdish Karamchandani said:
    DM8148 can't exist independently in board & certainly questions will come about design & interface with DM8148 like any other TI chips. Every customer buying DM8148 will have its own design. I understand it is custom design & I never asked any design help but just clarification/guidance on power sequencing to help me in design.

    You want someone to make your design for you, not support.

    I am trying to explain that your questions are not related to DM814x device or DM814x TI EVM, but to PMIC.

    2. Since TPS65232A2 is not recommended for new designs & we are not using PCIe feature can we eliminate this IC with below implementation,

    => We are having +24V rail so generate +5V from 24V rail & use 5V power good signal to enable separate 3.3V regulator. Again this 3.3V regulator will have input from 24V.

    just further query that assuming we are to use same TPS659113 can we ensure correct sequence by powering VIO section of TPS659113 from 5V (TPS_EVM_5V0) instead of 3.3V (TPS_BCK2_3V3)?

     

    In DM814x TI EVM we have this power sequence: TPS65232A2 -> TPS659113 -> DM814x device. And your above questions are related to power distribution between the two PMICs: TPS65232A2 -> TPS659113

    Unfortunately I am not familiar with PMIC (i.e. TPS659113) voltage input requirements, thus I recommended you to check PMIC documentation and ask/post in PMIC forum.