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.

DS90UB947-Q1: Confirm the difference in wiring length between lanes of different ports

Part Number: DS90UB947-Q1

Hi team,

The customer currently uses the dual PORT inputs of 947. LVDS shares a set of clock inputs. I understand that D0- and D0+ must be of equal length.
On the same port, for example:
Within what error do the trace lengths of D0+D0- of Port0 and D1+D1- of Port0 need to be controlled?
Do the lanes between different ports need to be of equal length, for example:
Do the trace lengths of D0+D0- of Port0 and D7+D7- of Port1 need to be controlled to be the same length? If necessary, what is our error requirement for trace length?

  • Hi Alan,

    The OLDI standard defines the max inter-pair skew between trace pairs. This is regardless of whether the traces are for Port 0 or Port 1. For inter-pair skew, the traces must be within 1 bit time (1 bit time = 1/7 * LVDS clock).

    Best,

    Jack

  • Hi Jack,

    Thanks for your help, but I still don't understand. Do Port0 (D0-D3) and Port1 (D4-D7) need to be of equal length? As shown below:

    Or do we just need to ensure that each pair of data lines is of equal length. Or the data lines in the same Port can be of equal length.

  • Hi Alan,

    Each pair of data lines needs to ideally be of equal length. Port 0 (D0-D3) and Port 1 (D4-D7) are recommended to be length matched. The general recommendation for OLDI signals is inter-pair skew within 60ps. Using a general rule of thumb of 6 in/ns for signal propagation, that would mean a max recommended difference in length of 0.36 inches.

    What is the max difference in length between Port 0 and Port1?

    Best,

    Jack