• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 11 subscribers
  • Views 125 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

AFE7901: Impedance matching

Maor Bouhadana
Prodigy 70 points
Part Number: AFE7901

Tool/software:

Hi, I'm a little bit confused. The datasheet says that the impedance of the TX port is a differential 100 ohm, but in some application notes and the layout I can see the impedance is a differential of 50 ohm. 
In the EVB scheme, we can see 2 types of Baluns - 1:1 and 1:2.
can you explain the cause?

  • 0
    TI__Mastermind 30170 points

    HI Maor,

    Typically differential traces for analog inputs are routed 50ohm single ended. Not 100ohm diff like on digital traces for LVDS, CML, etc.

    For the balun, different baluns, with different impedance ratios, were selected based on a few different application BWs that the device can cover.

    Regards,

    Rob

  • 0 in reply to Rob Reeder
    Prodigy 70 points

    When the datasheet says 

    what does it mean? can you clear the input impedance requirements for RX and TX? 

  • 0 in reply to Maor Bouhadana
    TI__Expert 4955 points

    Hi Maor,

    Tx is 50ohm output differential termination impedance for the AFE795x family. And 100ohm output differential termination impedance for the AFE790x family.

    For the Rx/FB channels, match using input differential impedance of 100 ohms.

    Best,

    Camilo