[SI-LIST] Re: optimal tline impedance
- From: "Alex Ippich" <dmarc-noreply@xxxxxxxxxxxxx> (Redacted sender "a.ippich@xxxxxxxxx" for DMARC)
- To: "sherman.chen@xxxxxxx" <sherman.chen@xxxxxxx>, Scott McMorrow <scott@xxxxxxxxxxxxx>
- Date: Mon, 26 Jan 2015 14:57:27 +0000 (UTC)
Sherman,
it does not really matter, if the PCB vendor shoots for 85ohms or for example
79ohm or 87ohm. As long as they do not have to use extreme line widths or end
up with the need to choose a material with very low or very high resinÂ
content, they are all similar in difficulty.
However, we all like to use things, that have worked in the past. So if you
stick with "standard" / typical impedance values, the PCB vendor may have used
a construction in the past, that fulfills your needs. So instead of using a new
stripline building block and having to optimize again, they like to use
building blocks, they already have optimized.
So from this second argument, there is some merit in staying with the 85 or 100
ohms.
Best regards,alex
Â
From: "Chen, Sherman" <sherman.chen@xxxxxxx>
To: Scott McMorrow <scott@xxxxxxxxxxxxx>
Cc: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
Sent: Monday, January 26, 2015 8:04 AM
Subject: [SI-LIST] Re: optimal tline impedance
Thanks.
Any practical concern from PCB vendor such as they are more deft in 85Ohm or
100Ohm impd control?
Best Regards,
Sherman Chen
Signal Integrity
EMC Global Hardware Engineering
Tel: +86 21 60951100-3329
From: Scott McMorrow [mailto:scott@xxxxxxxxxxxxx]
Sent: Monday, January 26, 2015 10:05 AM
To: Chen, Sherman
Cc: si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] optimal tline impedance
The answer to your question is ... yes. A statistical channel simulation will
help to show where the channel impedance will be centered.
On Jan 25, 2015 8:40 PM, "Chen, Sherman"
<sherman.chen@xxxxxxx<mailto:sherman.chen@xxxxxxx>> wrote:
Hi,
This idea may incur some controversial. Hope it's worthwhile.
It's like this:
In channel design, the optimal tline impedance actually depends on the fixed
impedances of TX, RX, and connector, etc. Through optimization you can locate
the best impedance for the trace, and it's not necessarily 85Ohm or 100Ohm. In
this case, to explore every cent of the system performance potential, should we
jump out of the frame of 85Ohm/100Ohm and choose to use other values?
Best Regards,
Sherman Chen
Signal Integrity
EMC Global Hardware Engineering
Tel: +86 21 60951100-3329
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