Crosstalk Questions

What is cross talk?

Switching of the signal in one net can interfere neigbouring net due to cross coupling capacitance.This affect is known as cros talk. Cross talk may lead setup or hold voilation.



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How can you avoid crosstalk?

-Double spacing=>more spacing=>less capacitance=>less cross talk

-Multiple vias=>less resistance=>less RC delay

-Shielding=> constant cross coupling capacitance =>known value of crosstalk

-Buffer insertion=>boost the victim strength

How shielding avoids crosstalk problem? What exactly happens there?

-High frequency noise (or glitch)is coupled to VSS (or VDD) since shilded layers are connected to either VDD or VSS.

Coupling capacitance remains constant with VDD or VSS.

How spacing helps in reducing crosstalk noise?

width is more=>more spacing between two conductors=>cross coupling capacitance is less=>less cross talk

Why double spacing and multiple vias are used related to clock?

Why clock?-- because it is the one signal which chages it state regularly and more compared to any other signal. If any other signal switches fast then also we can use double space.

Double spacing=>width is more=>capacitance is less=>less cross talk

Multiple vias=>resistance in parellel=>less resistance=>less RC delay

How buffer can be used in victim to avoid crosstalk?

Buffer increase victims signal strength; buffers break the net length=>victims are more tolerant to coupled signal from aggressor

what is the difference between crosstalk noise and crosstalk delay?
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