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TPS51206: Only VTTREF case

Genius 15590 points
Part Number: TPS51206
Other Parts Discussed in Thread: TPS51200

Hello,

I have 2 questions for TPS51206.

1.

My customer usually uses TPS51206 for DDR circuit.
But their new project requires only VTTREF and doesn't need VTT.
In that case, do we have any other better device than TPS51206?

2.
I have checked the below post for VTT unused case of TPS51206.

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/945053/tps51206-vtt-unused-case

Then I have an additional question.
Can the capacitor on VTT be removed in this case?

Regards,
Oba

  • Oba,

    In response to your questions, I have the following answers:

    1. I do not believe that only VTTREF is considered a typical case, so I do not believe that we have any parts geared towards VTTREF but not VTT. However, devices can be found that are just LDOs that output at the fixed voltage required with 10mA of current, but they may require more external components, as the divider for VDDQSNS is internal to this part.

    2. Theoretically speaking, if the VTT output is never used, then a capacitor on it would not be necessary for stability, as it never turns on. As an example, here is a diagram from the datasheet where only VTTREF is on - you can see that VTT stays off:

    In this case, it should not be necessary to have the capacitor on VTT, as it stays completely off. I should stress though that this is not a typical use case, and TI cannot guarantee operation outside of the typical parameters specified in the datasheet.

    Thanks,

    Kadeem

  • Hello, the alternative part in our portfolio is TPS51200. Please check this link and let me know for further support.

    (1) TPS51200: Reference output - Power management forum - Power management - TI E2E support forums

    Regards

  • Hello Oba,

    please close this thread as resolved if it answers your question.

    Regards

  • Hello Mahmoud,

    Thanks for your alternative part number infomration.

    Hello Kadeem,

    Thanks for your reply.
    VTTREF=ON, VTT=OFF with S3=LO and S5=HI is within the specification. The datasheet specifies this usage.
    So I don't think it is out of spec. What is your concern? Why this usage can't be guaranteed?

    Regards,
    Satoshi Obata

  • Satoshi,

    Realistically, I do not believe that there will be any concern with not having a capacitor on this pin - if VTT is completely unused, it should not require a capacitor.

    What I mean by the "TI cannot guarantee" is that the case of not having a capacitor on the pin whatsoever is outside of the specifications listed in the datasheet, therefor, we cannot assure that it will not cause any issue.

    Having said that, based on the functional block diagram below, there is no connection between VTTSNS and VTTREF, I cannot see any reason why this capacitor cannot be removed altogether.

    Thanks,

    Kadeem

  • Hello Kadeem,

    Thanks, I understand.

    Regards,
    Oba

  • Oba,

    Perfect. Please reach out if you have any further questions.

    Thanks,

    Kadeem