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DS90UB948-Q1EVM: Termination resistor

James Zhan
Expert 4365 points
Part Number: DS90UB948-Q1EVM

Hi team,

On the guide of 948 EVM mention that the 100ohm resistor should be placed to 948.

But I am wondering if these 100ohm resistor should be close to the connector?

Thanks.

  • 0
    TI__Mastermind 31590 points

    Hi James,

    Thank you for reaching to us. The 948EVM was designed for dual device 940/948. There are couple reasons for the 100Ω resistor spacing. The resistor placement closer to the device is mainly for CSI. The 100Ω resistor in between N and P are for VOD measurement. Basically, the pad spacing is for probe. For 948, if you need 100Ω termination, the placement of the resistor should be at the end of the connector. This will allow to terminate at the end of a transmission line in the case of EMC or bench testing purposes. Normally, the termination is at the panel side.

    Hope this helps. Let me know if you have further questions.

    Aaron

  • 0 in reply to Aaron Heng
    TI__Expert 4365 points

    Hi Aaron,

    Could you please help to explain why CSI need the 100ohm resistor close to the device? I mean CSI is just another interface.

    Thanks.

    Aaron Heng said:
    The resistor placement closer to the device is mainly for CSI.

  • 0 in reply to James Zhan
    TI__Mastermind 31590 points

    Hi James,

    Yes you are correct. CSI is another interface that supports in DS90UB940 device whereas DS90UB948 supports OLDI interface. Since you are working on the 948 device, you do not need CSI interface. So, the resistors at the device are neglected.

    Aaron

  • 0 in reply to Aaron Heng
    TI__Expert 4365 points

    Hi Aaron,

    But I am still wondering why would EVM place the 100ohm close to the IC?

    Thanks.

    James 

  • 0 in reply to James Zhan
    TI__Mastermind 31590 points

    Hi James,

    Please refer to my first posted. It is for Vod differential or single-ended measurement.

    Aaron