[FAQ] High-speed PCB layout: Tightly coupled vs loosely coupled

Joey Jin

Part Number: DS90UB962-Q1

Hi,Team

In datasheet layout session , Why we recommend that S>3W between RIN+ and RIN- trace ? Don't they need Tightly coupled or Loosely coupled?

over 3 years ago

0 Vijaya Ceekala over 3 years ago

TI__Intellectual 2930 points

Hello Joey

It is recommended to keep S>3W, so we keep these loosely coupled. Note that because they are differential signals, due to miller effect, any differential capacitance between + and - will manifest as 2xCdiff to Ground(or reference plane) if they are routed too closely

Thanks

Vijay

0 Joey Jin over 3 years ago in reply to Vijaya Ceekala

TI__Intellectual 2680 points

Hi, Vijaya,

Thank you !

Also I ware that different documents show different S&W range about Tight couple VS Loose couple .

Generally speaking, which S&W range is Tightly couple and which S&W range is Loosly couple?

+1 Vijaya Ceekala over 3 years ago in reply to Joey Jin

TI__Intellectual 2930 points

Joey

Usually 'tightly coupled' means you have greater than 2% cross talk between two lines. Two traces are tightly coupled if they are separated by 1W. So if S<=1W, they are tightly coupled

Loosely coupled would not have any cross talk and this is achieved if S>=3W

Thanks

Vijay

0 Joey Jin over 3 years ago in reply to Vijaya Ceekala

TI__Intellectual 2680 points

Thank you very much! Vijaya

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[FAQ] High-speed PCB layout: Tightly coupled vs loosely coupled