[SI-LIST] Re: Routing diff pair HDMI signals at 85 Ohms
- From: Michael Vrbanac <vrbanacm@xxxxxxxxxx>
- To: mgreim001@xxxxxxxxx
- Date: Tue, 18 Dec 2012 13:15:12 -0600
Thanks, Michael for that link.
Its always good to see free and openly published work that shows the
world hasn't changed much since my work the mid-late 90's with regard to
signaling in this fashion at rates higher than that in the same
materials, et al. However, from my experience, I'd really be careful
drawing many conclusions based on 85 ohms in measurement systems tuned
for 50 & 100 ohms without some more rigorous determination of potential
measurement error and the overall effect that loss might provide in
diminishing reflections. A 15% deviation in target impedance seems like
a lot room for that (rho +/-8% at every Z transition) while still making
one feel a bit too comfortable about it than it should. The rest of the
group might feel otherwise but I'd want to really ring that out before
committing to something like that. I see the potential of depending on
the system interconnection loss and then later use higher performance
materials in a similar setting and then wonder what happened when
troubles come up.
Best Regards,
Michael Vrbanac
On 12/17/2012 6:27 AM, Michael Greim wrote:
> Here is an interesting article by Samtec and Teraspeed looking at
> 85 and 100 ohms and their connector. Their may be useful data
> regarding loss for you.
> http://www.samtec.com/documents/webfiles/technical_library/app-note_SEAM-RA_SEAF-RA_pci-express-gen3_web.pdf
>
> -Michael.
>
> On Mon, Dec 17, 2012 at 1:33 AM, Sen Velmurugan
> <sen.velmurugan@xxxxxxxxxx>wrote:
>
>> There is an Intel app note on this for PCI express bus.
>> Thanks
>> Sen
>>
>>
>> On 12/16/2012 10:06 PM, FreeLists Mailing List Manager wrote:
>>> ----------------------------------------------------------------------
>>>
>>> Msg: #1 in digest
>>> From: miner_tom Cipollone <tom_cip_11551@xxxxxxxxxxx>
>>> Subject: [SI-LIST] Routing diff pair HDMI signals at 85 Ohms as opposed
>> to 100
>>> Date: Mon, 17 Dec 2012 00:19:24 +0000
>>>
>>> I was told recently that in order to help reduce radiated emissions in
>> HDMI signals, routed from a PCB to an HDMI connector, that it was better to
>> route the signals at 85 Ohms differential as opposed to 100 Ohms
>> differential.
>>>
>>> The contention was that with added connector L/C the overall average
>> impedance normalized closer to 100 Ohms.
>>> Is there any credence to this? Is there any research material that
>> agrees with this?
>>>
>>> (Hi Nazish)
>>>
>>> Thank You
>>> Tom
>>>
>>>
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