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LMH0387 Layout Questions

Mark Sauerwald88474
Genius 13475 points
Other Parts Discussed in Thread: LMH0387

With the LMH0387 should I be removing the ground plane beneath the loop filter capacitor?

 That is C11 on the SD387 evaluation board.

 I just can’t make it out from the PDF.  Is there ground plane  or not.

Also, a long shot, is it possible to use TERM_TX, pin 45 as a second output?

 

  • 0
    TI__Genius 13475 points

    We often remove ground plane from beneath critical components for two reasons:  it will reduce the parasitic capacitance to GND, and it will decrease noise coupling from GND.   In the case of the LMH0387, the capacitor connected between pins 20 and 21 is used by the cable equalizer in a loop which sets the amount of equalization to apply.  The bandwidth of this loop is very low, so we don't worry much about noise injection or parasitic capacitances there.  Whatever you do with the GND plane under that cap will be good.

    And alas, no, you cannot use TERM_TX as a second output....