• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 11 subscribers
  • Views 268 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

AFE7903: Clocking of AFE79xx with LVPECL

Christian Ryffel
Prodigy 140 points
Part Number: AFE7903
Other Parts Discussed in Thread: LMK5B12204

Hi

We would like to clock the AFE79xx with an LMK5B12204. The best noise performance seems to be LVPECL for interfacing. Do you have any recommendation how to connect them?

The datasheet of the AFE has nearly no information about the infrastructure. And for the LMK it's not clear what the settings in the register really do. Do they just change the drive current? Also the 220Ohm resistors mentioned in https://www.ti.com/lit/pdf/slla120 seems to be not necessary as according to the LMK datasheet.

Best

Christian

  • 0
    TI__Mastermind 37960 points

    Hi Christian,

    Connecting an LVPECL clock interface to the AFE79xx would be suggested to use a standard interface. As long as the clocking circuits meets the min/max levels of the input clock and doesn't exceed the abs max.

    As for the LMK questions, I can forward this on to the clocking team to help address.

    Regards,

    Rob

  • 0 in reply to Rob Reeder
    Prodigy 140 points

    Hi Rob

    Yes please, forward it to the clocking team. It's more a question about the LMK. I've asked because the common mode voltage of the receiver is mentioned and there are no information about it in the AFE datasheet.

    Regards

    Christian

  • 0 in reply to Christian Ryffel
    TI__Expert 3095 points

    Hi Christian,

    LMK5B12204 provides AC-LVPECL which has different circuity than traditional LVPECL so it does not require the resistor for current return path.

    AFE Fref requires AC-coupling so you would need to have AC-coupling caps on the path between LMK and AFE.

    -Riley