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LMK00804B-Q1: The layout suggestion for lmk00804

Lijia Zhu
Expert 5730 points
Part Number: LMK00804B-Q1
Other Parts Discussed in Thread: LMK00804B,

Hi team,

I have a question about the clock buffer lmk00804b. My board is big so the clock source is far away from the load(drvice need the clock, such as ADC). Should I put the clock buffer close to clock source or close to the load? The distance between source and load is about 30cm. Clock freq is 100M. Any other advice/comments for the layout?

B&R

Lijia

  • 0
    TI__Genius 16615 points

    Hi Lijia,

    What input termination does the design use? A differential input such as LVPECL is preferred for your design because the differential signal will use less power at longer traces than single ended. The clock buffer can then be placed close to the load since the outputs are single-ended, which will draw more power if they are placed far from the load.

    Also, make sure to place the 43-Ω series termination resistors as close to the Qx outputs as possible at the launch of the 50-Ω traces. (Details under 11.1.5 in the datasheet)

    You can also confirm the affects of the trace length by simulating the design with the Hyperlynx Signal Integrity tool from Mentor Graphics. Check the waveform at the load. The LMK00804B-Q1 IBIS model can be found at https://www.ti.com/product/LMK00804B-Q1#design-development##design-tools-simulation.

    Regards,

    Jennifer