[SI-LIST] Re: stripline differential impedance control issue

  • From: steve weir <weirsi@xxxxxxxxxx>
  • To: ZYL <sango@xxxxxxx>
  • Date: Wed, 10 Nov 2010 00:42:49 -0800

The impact of truly orthogonal traces on adjacent layers is minimal. The 
impedance will not drop significantly unless you have tandems on L7 and 
L8, or patches on one layer that signals from the other run over.

Steve
ZYL wrote:
> Thanks for you feedback Steve
> Our design can only realize 100 diff stripline impedance by routing on 
> layer 7 or layer 8, but ref. to layer 6 and layer 9
> so the layer 7 digital/power signals will quite close to layer 8 HDMI 
> signals
> My concern is with this kind of routing, is that big impedance drop 
> might happen? example from 100ohm to 80ohm?
> It's very difficult to simulate, since all signals in layer 7 should 
> have load, without load, simulation shows that no big impact to 100ohm 
> diff. impedance on HDMI signal
> Br
> Sango
>
> At 2010-11-10 15:34:11úČ"steve weir" <weirsi@xxxxxxxxxx 
> <mailto:weirsi@xxxxxxxxxx>> wrote:
>
> >Are you asking if you can route HDMI in L7 as well as L8?  Or are you 
> >asking about impedance only in L8?
> >
> >L7 HDMI, is a matter of how close you get to the digital / power signals. 
> >
> >L8 impedance:  There is no reason from what you show that you cannot get 
> >100 Ohms differential in L7 and L8.  It depends on your materials, 
> >spacing, and trace parameters.
> >
> >Steve.
> >ZYL wrote:
> >> Hello Everyone
> >> I got one problem related to PCB layout design for HDMI differential 
> >> signal. 
> >> Actualy, since layout area is so limited, we have to route some traces 
> >> above HDMI differnetial signal in adjacent layer, like below
> >> Layer 6: ref. GND;
> >> Layer 7: lots digital/power signals (horizental)
> >> Layer 8: HDMI differential pairs (vertical)
> >> Layer 9: ref. GND 
> >> Can someone let me know how much impact will get by this kind of routing? 
> >> Is that possible to meet 100ohm diffenertial impedance by this routing?
> >> Thanks
> >> Best Regards
> >> Sango
> >>  
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> >-- 
> >Steve Weir
> >IPBLOX, LLC 
> >150 N. Center St. #211
> >Reno, NV  89501 
> >www.ipblox.com
> >
> >(775) 299-4236 Business
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>
>


-- 
Steve Weir
IPBLOX, LLC 
150 N. Center St. #211
Reno, NV  89501 
www.ipblox.com

(775) 299-4236 Business
(866) 675-4630 Toll-free
(707) 780-1951 Fax


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