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TMS320C6748 - Unused USB Interface 1.2V Power Supply

AmandaD
Prodigy 140 points

Hi,

I will be using the TMS320C6748BZWTD4 with a core voltage of 1.3V.

I won't be using the USB port but from the datasheet it looks like I still need to connect USB_CVDD to 1.2V.  1.2V will also be connected to filters on the PLL_VDDA and PLL_VSSA lines.

1.2V will not be used anywhere else on my board.

Could you give me an indication of the current that will be required for these 1.2V connections?

I've seen that the maximum operating conditions for these supplies is -0.5V to 1.4V but the recommended operating voltage is 1.14 to 1.32V.  I'm assuming that I can't connect them directly to the 1.3V supply which has a recommended tolerance of 1.25V to 1.35V.

Thanks, Amanda

  • 0
    TI__Guru**** 176811 points

    Amanda

    USB_CVDD must still be connected to 1.2V.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Prodigy 140 points

    David,

    Ok, I can connect USB_CVDD and the PLL filters to the 1.2V supply but how much current will they draw?

    I can't design a power supply for them until I know this and the power calculation spread sheet doesn't give information for a 1.2V supply, only CVDD & RVDD (1.3V), Static (?V) IO18 (1.8V) and IO33 (3.3V).

    Thanks,

    Amanda

  • 0 in reply to AmandaD
    TI__Guru* 83855 points

    Hi Amanda

    Column AA in the c6748/46/42 Power Spreadsheet (Rev D) is what represents the "static" supplies, if you hover over the word "Static" you will see the comments, which calls out that the column comprehends several static 1.2V supplies (PLLx_VDDA, SATA_VDD, RTC, USB_CVDD).

    The USB CVDD power is negligible when USB is not used. If you select USB HS/FS transmit/receive, you will see the USB _CVDD power consumption under the static column for the USB row.

    Hope this helps.

    Regards

    Mukul

  • 0 in reply to Mukul Bhatnagar
    Prodigy 140 points

    Hi Mukul,

    Thanks for your response.  I think I'd looked at this column but since it didn't show anything for the USB_CVDD I'd assumed that there must have been something wrong.  Not that the current drawn was insignificant. :)

    Regards,

    Amanda