[SI-LIST] USB and SATA Common-Mode Impedance - Q on importance

Hi All,
 

In reviewing the USB and SATA specs I noticed that the Zcm  (Common-mode
impedance) is defined for the respective cable assemblies. However the
Zcm id NOT spec'd
for the circuit board construction, which leads to the following
questions that I 
hope some folks can help me with:

 

1.      How important is the Zcm for USB and SATA?
2.      Should the Zcm for the pwb be matched to the cables?
3.      HDMI does not spec Zcm for cable or pwb. Is this an oversight?

 

 

(With due deference to EricB - but I have to use the terminology from
the standards!)

 

 

Best Regards
Charles Grasso
Compliance Engineer
Echostar Communications Corp.
Tel: 303-706-5467
Fax: 303-799-6222
Cell: 303-204-2974
Pager/Short Message: 3032042974@xxxxxxxxx
<BLOCKED::mailto:3032042974@xxxxxxxxx> 
Email: charles.grasso@xxxxxxxxxxxx
<BLOCKED::mailto:charles.grasso@xxxxxxxxxxxx> 

 


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