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TMS320C6655: Handling of VDDTn pin when Serdes is not used

UNA
Mastermind 7980 points
Part Number: TMS320C6655

Hi,

In the case that Serdes is not used, it is described in "Hardware Design Guide for KeyStone I Devices Application Report" that VDDTn can be connected to DVDD15. Are decoupling capacitors unnecessary in this case?

Best Regards,
H.U

  • 0
    TI__Guru**** 161600 points
    Hi,

    There is no need for decoupling on VDDT, when SerDes is not used. See Table 6-1. Power Supply Rails on C665x from the device datasheet:
    VDDT1 -> Filtered version of CVDD1. Special considerations for noise. Filter is not needed if HyperLink is not in use.
    VDDT2 -> Filtered version of CVDD1. Special considerations for noise. Filter is not needed if SGMII/SRIO/PCIE is not in use.

    Best Regards,
    Yordan
  • 0 in reply to Yordan Kovachev
    TI__Mastermind 42545 points
    Hi,
    Note that there was a typo in the current an earlier versions of the Hardware Design Guide. When the serdes interfaces are not used the VDDTn inputs should be connected directly to the CVDD1 1.0V supply. This is the same supply used when the filter is connected but without the filter components.
    Regards, Bill