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ADS54J60EVM: About LMK04828 clkin1 input impedance matchingquestion

Part Number: ADS54J60EVM
Other Parts Discussed in Thread: LMK04828

Dear TI,

I'm using clkin1 as external clock input with 100Mhz frequency and find in schematic R42 is not connect. However, from user guide LMK04828, if use clkinX as single end input, there should be a 50ohm resistance to match the impedance. Should I add R42 manually for better performance? Attached is the evaluation board schematic and LMK04828 user guide page 104. Thanks advance for your help.

Shuyi Liu

  • Shuyi,

    I am not 100% sure how much this will help, but feel free to try this. Ideally, R42 and C81 should be placed as close as possible to the LMK, but on this EVM, they are not as close as they could have been. Based on this placement and the frequency you use for the external clock, adding this resistor may or may not help.

    You may have to apply more power from your signal generator with this termination resistor added.

    Regards,

    Jim