• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 33 subscribers
  • Views 57 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.

DP83822I: Connection with LVPECL for 100BASE-FX

Atsushi Takahashi
Expert 1415 points
Part Number: DP83822I

Tool/software:

Hi Team,

My customer would like to use DP83822IRHBR for 100BASE-FX.
The I/O of the optical module that connects to PHY is LVPECL.

1) Can DP83822IRHBR communicate with LVPECL I/O module?
2) Please tell me VOH/VOL of TD_M/TD_P.
3) Please tell me VIH/VIL, Vcm of RD_M/RD_P.

Best Regards,

  • 0
    TI__Genius 12916 points

    Hi Takahashi-san, 

    DP83822 is a current mode driver so it utilizes CML. The Vcm of DP83822 depends on what DP83822's AVD is. 
    The customer can connect to LVPECL by putting a decoupling capacitor and putting pullups to the Vcm of the LVPECL. 

    We do not have VOH/VOL and VIH/VIL information at the moment. 
    However, we require input signal to have 0.22 to 1.8 Vpk-pk and we transmit 1Vpp. 

    Best,
    J

  • 0 in reply to J
    Expert 1415 points

    Hi J-san,

    Thank you for your reply.

    For example, if the customer is using the DP83822 with AVD = 3.3V(or 1.8V), does that mean I can connect it to LVPECL of opt module by pulling up TD_M/TD_P and RD_M/RD_P to 3.3V(or 1.8V) with a decoupling capacitor?

    In this case, are there any restrictions related with the conditions of use of LVPECL?

    I'm not familiar with this kind of interface specifications, so I apologize if this is a poor question.

  • 0 in reply to Atsushi Takahashi
    TI__Genius 12916 points

    Hi Takahashi-san, 

    Your understanding is correct. 
    On the LVPECL side, the correct termination and correct swing will have to be set. 
    The same would apply for DP83822. The customer can refer to the datasheet for information on receiver input swing and TX swing. 
    Please refer to this document for more information: https://www.ti.com/lit/an/scaa056/scaa056.pdf?ts=1752596177144&ref_url=https%253A%252F%252Fwww.google.com%252F

    And this is the general idea to interface between DP83822 and LVPECL module:


    Best,
    J