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LMH0384: return loss measurement

Satoshi Yone
Expert 3600 points
Part Number: LMH0384

Hi, Team,

For LMH0384 ac coupling capacitor, I have a question for the return loss measurement.

The customer layout is 1005, but the mounted capacitor is 0603. Is there a concern when we measure the return loss of this board?

I think that this cause a bad return loss result, but the data doesn't have an issue. They finally use 0603 layout with 0603 capacitor.

Best Regards,
Satoshi Yone

  • 0
    TI__Guru* 88895 points

    Hi Yone-San,

    Customer layout is 1005 but 0603 form factor capacitor is used. 1005 Cap could have a higher parasitic capacitance. Also, to a large degree this depends on the pcb layout as well. If there is no ground or VCC under capacitor pads then this parasitic capacitance is minimized.

    In summary, using a 0603 cap on 1005 pads could be ok. Please make sure there is return loss margin - at least 2-3dB - just to make sure we have enough margin for part to part or board to board variations.

    Regards,,nasser