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OPA653: LAYOUT with ground plane cuts

Renan Santos Adriano
Mastermind 18385 points
Part Number: OPA653
Other Parts Discussed in Thread: OPA659EVM

Hi Team, 

Goo day.

My customer is looking into our OPA659EVM layout. There is a window open in all of the ground and power planes around the IC. In this case, 50 ohms of microstrip lines connecting to inputs do not have a ground plane underneath. Is not this a problem input-output matching? Please see attached snapshots.

Regards,

Renan

  • 0
    Guru 140200 points

    Hi Renan,

    if the traces are as short as possible (which they are here), then it doesn't matter. Important is that the ground plane is reaching up to the termination resistors and that these termination resistors are mounted as close as possible to the OPAmp package (which they are here).

    Kai 

  • 0
    TI__Genius 15555 points

    Hello Renan,

    Having the GND/Power planes underneath the pins will cause provided unwanted parasitic capacitance on the input/output, which can be a cause of instability and might limit the bandwidth of your device.

    Best,

    Hasan Babiker