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DS90UB947-Q1: Power pins description

William Taylor
Prodigy 90 points
Part Number: DS90UB947-Q1

Hi at TI, I am working on a design using the 947 and 948 parts.

I just can't seem to find at all a detailed description of the power pins on these devices.

For example, referring to the 948 there is VDD12_LVDS VDDP12_LVDS VDDL12_0 VDDL12_1 VDDP12_CH0 VDDR12_CH0 VDDP12_CH1 VDDR12_CH1 among others.

Maybe I do not need to know too much but I am trying to make sure the interfaces to other devices will work as there is an FPGA and of course a processor in the system too.

So, is there a Tech note in the system somewhere and I just haven't looked hard enough?

Thanks in advance for your help

William

  • 0
    TI__Guru 66810 points

    Hi William, 

    Thanks for reaching out. 

    TI's recommendation is to exactly follow the Typically Application diagram filtering structure for these rails.

    For guidance on approximate pin power/current consumptions and noise/tolerance information, this is in each datasheets' Specification tables.

    Regards, 

    Logan

  • 0 in reply to Logan Cummins
    Prodigy 90 points

    Thanks very much Logan, and yes I have followed the data sheet to the letter so no problems there. I was just wondering for example which rail powers the lvds outputs?

    And I forgot another question, the 948 data talks of placing pull downs on unused pins but there is no mention of that for the 947. Could you clarify for me? And what typical resistor values assuming best not to tie to ground.

    Thanks again Logan.

    William 

  • 0 in reply to William Taylor
    TI__Guru 66810 points

    Hi William, 

    We don't really differentiate each rail, as some might be directly tied or indirectly tied to OLDI block or data in/out of OLDI block. 

    Leaving them floating may lead to unwanted radiated noise in EMC testing depending on the device configuration and the pins may float to a unknown value based on leakage current. So generally it is recommended to use pulldowns per the datasheet recommendation. Value is not super critical, user's choice in the 1k to 10k+ range is fine. 

    Regards, 

    Logan

  • +1 in reply to Logan Cummins
    Prodigy 90 points

    Great, thanks Logan, I've already placed 10K's so that's good.

    Cheers

    William