[SI-LIST] Re: Maximum frequency consideration for high-speed digital analysis of differential signals
- From: "Tom Dagostino" <tom@xxxxxxxxxxxxx>
- To: <Cortex.Chen@xxxxxxxxxxxx>, <esayre3@xxxxxxxx>
- Date: Sun, 8 Jan 2006 19:26:10 -0800
The 0.35 factor is for a 2 pole critically damped system.
Tom Dagostino
Teraspeed(R) Labs
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065
tom@xxxxxxxxxxxxx=20
www.teraspeed.com=20
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
401-284-1827
-----Original Message-----
From: Cortex.Chen@xxxxxxxxxxxx [mailto:Cortex.Chen@xxxxxxxxxxxx]
Sent: Sunday, January 08, 2006 6:44 PM
To: esayre3@xxxxxxxx
Cc: tom@xxxxxxxxxxxxx; rula.bakleh@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: RE: [SI-LIST] Re: Maximum frequency consideration for
high-speed digital analysis of differential signals
Ed,
Actually, refer to the page 330 of High-Speed Digital System Design - A =
Handbook of Interconnect Theory and Design Practices.
V =3D Vin (1-e -t/t)
If Vin is assumed to be 1V, then
t80% =3D 1.609t
t20% =3D 0.223t
t20~ 80% =3D 1.386t
F3dB=3D 1/2pt ----> t=3D 1/2pF3dB
t20~ 80% =3D 1.386/2pF3dB =3D 0.22/F3dB
? F3dB =3D 0.22 / t20~ 80%
Regards,
Cortex
-----Original Message-----
From: Ed Sayre III [mailto:esayre3@xxxxxxxx]=20
Sent: Friday, January 06, 2006 11:48 PM
To: Cortex Chen (???)
Cc: tom@xxxxxxxxxxxxx; rula.bakleh@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] Re: Maximum frequency consideration for =
high-speed digital analysis of differential signals
Cortex,
The value of 0.35 in your calculation is base on the pole location =
of=20
the 1st order system. How are you deriving the 0.22 value?. I am very=20
curious to understand the thinking behind this.
Regards
-Ed
At 10:25 AM 1/6/2006 +0800, Cortex.Chen@xxxxxxxxxxxx wrote:
>0.35/Tr ---- 10% to 90%
>0.22/Tr ---- 20% to 80%
>
>Regards,
>
>Cortex
>________________________________
>
>From: si-list-bounce@xxxxxxxxxxxxx Nz Tom Dagostino
>Sent: 2006/1/6 [P] W 10:03
>To: rula.bakleh@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: Maximum frequency consideration for high-speed=20
>digital analysis of differential signals
>
>
>
>I'm not sure how you are computing your bandwidth. If you have a 25 =
psec
>risetime (assuming 10-90%) your -3dB bandwidth is 0.35/25psec or 14 =
GHz.
>
>When analyzing bandwidth requirements for systems like this most people =
talk
>about passing the 3rd or 5th harmonic of the clock. In your case that =
is
>7.5 or 12.5 GHz. Some analysis of your system requirements is in =
order.
>
>Tom Dagostino
>Teraspeed(R) Labs
>13610 SW Harness Lane
>Beaverton, OR 97008
>503-430-1065
>tom@xxxxxxxxxxxxx
>www.teraspeed.com
>
>Teraspeed Consulting Group LLC
>121 North River Drive
>Narragansett, RI 02882
>401-284-1827
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx
>[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of =
rula.bakleh@xxxxxxxxxx
>Sent: Thursday, January 05, 2006 2:19 PM
>To: si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Maximum frequency consideration for high-speed
>digital analysis of differential signals
>
>
>Hi Everyone,
>
>
>I'm designing a differential signal for the Rocket I/O interface. My =
signal
>speed is 5 Gbit/sec, operating frequency is 2.5 GHz, and fastest edge =
rate
>is 25 psec or 40 GHz.
>
>
>
>In regards to performing channel analysis, what is the highest =
frequency
>content to consider when designing this particular differential signal
>serial link? If I am measuring or simulating S parameters for various
>portions of this link what is the highest frequency of interest that I =
need
>to consider as a rule of thumb and why?
>
>
>
>Is it the operating frequency only, multiples/harmonics of the =
operating
>freq, edge rate frequency (f=3D1/trise), multiples/harmonics of the =
edge rate
>freq, or some fraction of the edge rate? I'm finding conflicting
>information: some people say that it's the full edge rate, others say =
0.35
>or 0.5 of the edge rate, and yet others say multiples of the edge =
frequency
>should be taken into account for analysis and design. I'm hoping that
>somebody could shed some light on this topic for me.
>
>
>
>Thank You,
>
>Rula Bakleh
>
>
>
>
>
>
>
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