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CDCV304 input high threshold

Greg Ramon
Prodigy 60 points
Other Parts Discussed in Thread: CDCV304

I've been using the CDCV304 in many application as a high speed clock buffer/fannout.  However, in this new application, I wonder if I am doing something I should not be with this part.  I'm AC coupling (DC block) a high speed CMOS signal (0 to 3V) and feeding it into the clock input of the CDCV304.  Therefore my signal is now swinging -1.5V to +1.5V going into CDCV304 input.  It seems to be working okay like this but the datasheet says on page 5 that VIH(min) is 0.5VDD (1.65V for me).  Is there an internal DC bias that would bias the signal up again?

  • 0
    TI__Expert 3985 points

    Hi Greg,

    first of all, thanks for your attention in our device. You are right when you say that in datasheet at page 5 it is written that the VIH(min) is 0.5VDD. But in the Electrical Characteristics table it is also written that the Input Voltage (VIK) can reach -1.2V, which is anyway not enough for your -1.5V.

    Unfortunately there is no circuit which bias up the signal again. This means that the IC may work, but we can not guarantee that all the figures specified in datasheet are then fulfilled.

     

    Best Regards,Do you have the possibility to insert some resistors in your board in order to provide datasheet compliant levels at the input of CDCV304?

    Leandro

  • 0 in reply to Leandro_z
    Prodigy 60 points

    I know what I have to do now, thanks.

    -greg