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TLK100 Transformer Termination

Other Parts Discussed in Thread: TLK100

Using a TLK100 in design and I have a question regarding the transformer terminations- the datasheet recommends the center taps be pulled to VDD.  There are many VDD on this part.  Does this mean the VDD33 rail or the VDD11 rail?  Thanks.

  • Hi Patrick,

    VDD33 is the I/O 3.3V supply.  VDD11 is the 1.1V Core Power Output.

    Please take a look at Figure 2-1. Power Scheme for Single Supply Operation [Page 10 of datasheet]

    Figure 2-1 shows the center taps connected to the 3.3V supply.

    Based on the above information, i'd say that the center taps should be pulled to VDD33.

    Best regards,
    Brian Gosselin


  • Hi Patrick,

      True, there are several internal power rails in the TLK100.  However the xfmr CT is connected to the main supply.  If you look at Fig 2-1 on page10, and Fig 2-2 on page 11, and most importantly Table 2-1 on page 12, you'll see the xfmr CT is always connected to the 3.3V rail, or the 1.8V rail, depending on what supplies are available for the TLK100 design.  Table 2-1 defines the scenarios for Single Supply and Lowest Power.



  • Patrick,

    Also, please take a look at Table 2-1. Power Supply Options.

    "Because the TLK100 incorporates independent voltage regulators, designers may take advantage of several optional configurations, depending on available power supplies."

    The center taps don't always have to be pulled to 3.3V - it depends on your configuration.

    However, it appears that the center taps are always connected to what VDD33 is connected to.

    Best regards,
    Brian Gosselin

  • Hi,