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TLK105 clock XI voltage level when using VDDIO 1.8V

jonds
Prodigy 110 points

Other Parts Discussed in Thread: TLK105

From the current datasheet (January 2014) it is not clear which voltage level has to be used for clock input XI.

Is it referenced to VDDIO (e.g. 1V8) or to AVDD33 (3.3V) ?

Can TI confirm that all other IO pins (e.g. led output, reset, pwrdn, ...) are referenced to VDDIO ?

Thanks,

Jon

 

  • 0
    TI__Mastermind 23675 points

    Hi Jon,

    Page 34 of the TLK105 datasheet has reference to the voltage. If using an external oscillator you "should be a nominal voltage of 3.3V". Yes, the LED pins, reset and pwrdn pins are all referenced to VDDIO.

    Regards,

    Ross

  • 0
    TI__Mastermind 23675 points

    Hi Jon,

    Are you operating in MII or RMII mode? It is important to note that RMII 1.8V VDD I/O is not supported. Are you using a crystal or external clock source? I am assuming external oscillator since you are only asking about XI. Is this correct?

    Regards,

    Ross

  • 0 in reply to Ross Pimentel
    Prodigy 110 points
    Hi Ross, I am aware of the stated limitation at 1.8V and will use MII, although there might be some chance that using RMII on the RX side output will actually work: in the tables at page 90/91 there is only some reference to VDDIO for the TX input timing and not for the RX output timing. (I only need the RX output). Most likely I'll be using a clock buffer (at 3.3V) to distribute the 25 MHz to the different PHY's. Thank you for the support, Jon
  • 0 in reply to jonds
    TI__Mastermind 23675 points

    Hi Jon,

    I just spoke with the team to clarify the clock inputs and here is what I found: 

    Even if you are using external clock source, the target levels should be the same as I/O Vdd (i.e. 1.8V). However, even if you external clock source is 3.3V, the internal circuity should still operate with these higher levels. 

    I will be making changes to our datasheet to make this more clear for future use.

    Sorry for the confusion.

    Regards,

    Ross