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DS90UB960-Q1: DS90UB960 FPD link AC coupling cap ground moat?

Oscar Yu69
Prodigy 60 points
Part Number: DS90UB960-Q1

Hi there,
I'm working on a product utilizing your DS90UB960 deserializer. I am wondering if the AC coupling capacitors used on the RIN pins (FPD-Link) need a moat underneath them? 
The 960 evaluation board layout appears to have moats underneath the capacitors but the datasheet guidelines do not specifically say to moat them:
image.png
Thank you.
Best,
Oscar
  • 0
    TI__Guru** 108360 points

    Hello,

    This is not a special requirement of the 960 but it is a general layout improvement.
    Once you are routing a differential pair and you need to branch out the traces to be able to place capacitors (which is the case here) then your impedance is not any more 100ohm but much less. Inorder to increase the impedance to minimize this impedance discontinuity, you need to add these GND relief layer below the landing pads.