[SI-LIST] 90 OHM Differential Impedance

  • From: Saril <saril_k@xxxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Sun, 21 Mar 2010 00:11:21 +0530 (IST)

Hi All,
Basically USB signals require 45 Ω  characteristic impedance and have a 
target differential impedance of 90 Ω. 
The 90 Ω Differential impedance can be achieved without having the single 
ended characteristics impedance of 45 Ω. Sometimes the Single ended 
characteristics impedance may be 50 Ω but still we can have the differential 
impedance of 90 Ω, if we tune the differential trace separation. 

How important is it to meet single ended as well as differential impedance 
requirements together, can I just neglect the single ended impedance and 
consider only the differential impedance value. 

Thanks in advance.

Saril Kaiprath

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