• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 33 subscribers
  • Views 375 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.

DS90UB954-Q1: Consultation on Layout Impedance

WU YISYUAN
Expert 2165 points

Part Number: DS90UB954-Q1

Hi,

The impedance of the mipi interface, TI's SerDes requires 100 ohms.
I used The SoC chip requires a mipi interface impedance of 90 ohms.

If so,which value should we take for the layout design.

thanks.

  • 0
    TI__Mastermind 30515 points

    Hello,

    pls see mipi DPHY spec., the HS receiver DC spec. has 100ohms differential input impedance request (range: 80ohms ~ 125ohms), also ub954 output typ. single-end impedance is 50ohms (diff. is 100ohms), so this is why TI recommends you to use the 100ohms PCB control, this impedance would impact the SOC's MIPI input SI issue but it doesn't impact 954's performance.

    regarding your issue why SoC asked you to select 90ohms, it is dependent on your SoC termination spec., you can compare it with MIPI spec. listed as below (in MIPI DPHY spec.1.3, page85,). Possibly it could be that SoC can get better SI performance if you use 90ohms as receiver. also pls note the PCB has some variation on impedance control.

    Table 24 HS Receiver DC Specifications 1065
    Parameter
    Description
    Min
    Nom
    Max
    Units
    Notes
    VCMRX(DC)
    Common-mode voltage HS receive mode
    70
    330
    mV
    1, 2
    ZID
    Differential input impedance
    80 (min)
    100 (typ.)
    125 (maximum)
    Ω
    3
    ZID_Open
    Differential input impedance in unterminated mode
    10K
    –
    –
    Ω