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Original question:

THS5641A: Request for schematic review

THS5641A: Issue with bring-up

Andrew Baek
Intellectual 925 points

Part Number: THS5641A
Other Parts Discussed in Thread: LMK04828

We finally have the board and are in the process of board bring-up.  There are no real issues so far.

The only thing is that the output from THS5641A shows no activity.

  • The digital input is a simple square wave switching between 0 and 255 at 5MHz rate
  • The clock is coming from LMK04828
  • Checked all the voltages and they are correct
  • Probed all the digital inputs and they are correct
  • The only potential issue could be the signal levels of the clock signal coming from LMK04828, which I've summarized in the attached pdf.

I have also included the schematic.

Please let me know if you have some suggestions.

Thanks,

Andrewnotes 040323.pdffibersense_v1p23.pdf

  • +1
    TI__Guru* 91947 points

    Andrew,

    If DVDD is 5V for the THS5641A, the clock input high-level needs to be at least 3.5V. 

    If DVDD is 3.3V for the THS5641A, the clock input high-level needs to be at least 2.1V. 

    I do not think the LMK can provide this high of a voltage level. You will need to confirm this with the the data sheet and the mode you are using for the output level.

    Regards,

    Jim

  • 0 in reply to jim s
    Intellectual 925 points

    Hi Jim,

    Just a follow-up.

    We used a 3.3V clock from FPGA and got THS5641A working.

    Thank you,

    Andrew