DS90UB960-Q1: layout questions

Kailyn Chen

Part Number: DS90UB960-Q1

Hello,

According UB960 datasheet, route RIN- trace with minimal coupling to RIN+ trace to meet S>3W rule, I need to confirm, if it meet the S>3W rule, it may not meet the 100ohm differential impedance. My customer routed the trace width is 4.8mil, and the interval of the differential signal is 6.2mil. So it doesn't meet the S>3W rule, could you please help to confirm if it is OK?

My customer routed the trace as this:( I recommended him to route the trace according to 100ohm impedance, Terminate RX- near the connector and switch RX+ to 50ohm single-ended trace.)

Best regards

Kailyn

over 4 years ago

0 Steven(Shenzhen) Shi over 4 years ago

TI__Mastermind 30515 points

Kailyn,

yes, you are right.

the 3w rule is not conflicted with impedance control. the impedance is dependent on many factors such as width, depth and material ect., the 3W rule is used for isolating the cross-talk, and the impedance should be controlled by these factors together.

regards,

Steven

0 Kailyn Chen over 4 years ago in reply to Steven(Shenzhen) Shi

TI__Genius 9560 points

Hi Steven,

Thank you very much, the impedance control decide the trace width, trace interval .etc, while the 3W rule need the trace interval equals to the three times width of the trace. For example, our customer routed the RIN+ and RIN- with trace width is 4.8mil, trace interval is 6.2mil, if according to the 3W rule, the trace interval should be 4.8*3=14.4mil? If this, does this meet the 100ohm impedance?

I am so sorry to interrupt you again.

Best regards

kailyn

0 Steven(Shenzhen) Shi over 4 years ago in reply to Kailyn Chen

TI__Mastermind 30515 points

The 3W rule is used for the single-end layout closed to the connector. Nearby the RIN+/RIN-, the 3w is not required but key point is that RIN+/RIN- trace should have 50ohms impedance control.

regards,

Steven

0 Kailyn Chen over 4 years ago in reply to Steven(Shenzhen) Shi

TI__Genius 9560 points

Hi steven，

Thank you very much.

Best regards

Kailyn

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DS90UB960-Q1: layout questions