[SI-LIST] Re: Bandwidth
- From: "Dagostino, Tom" <tom_dagostino@xxxxxxxxxxx>
- To: "'p2rich@xxxxxxxxxxxxx'" <p2rich@xxxxxxxxxxxxx>,si-list@xxxxxxxxxxxxx
- Date: Tue, 18 Sep 2001 15:04:37 -0700
The first reference I saw of 10-90% was in scopes and the equation used there
is BW = 0.35/Tr. The constant depends on the response of the "filter". The
0.35 number assumes a 2 pole critically damped Guassian response if I remember
correctly. Other responses will have different constants.
The 20-80% numbers I first saw were from Motorola ECL databooks in the 60's.
They used the 20-80 numbers because the transition characteristics of ECL were
fast in the middle and slow around the corners. If you used the 10-90 numbers
with ECL you would get an unrealistically slow number. The max dV/dT is the
critical issue for SI.
Hope this helps.
Tom Dagostino
Modeling Manager
Mentor Graphics Corp.
SAE
tom_dagostino@xxxxxxxxxx
503-685-1613
-----Original Message-----
From: Rich Peyton [mailto:p2rich@xxxxxxxxxxxxx]
Sent: Tuesday, September 18, 2001 12:21 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Bandwidth
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Hi all,
I have equations for:
a) bandwidth requirement = .361/Risetime.
b) f3dB =.35/Risetime
Are the above for 10% - 90% risetimes?
In reading "Electronic Packaging of High Speed Circuitry" by Konsowski &
Helland (any comments on book? mine- Good Reading )
it states that you should be using 20% - 80% for high speed signals and
states equation:
c) 3F = 1/trise (20-80%)
If I use a risetime of 1nsec. into the above equations I get:
a) 361 MHz
b) 350 MHz
c) 1GHz
Does anyone want to shed some light on this and comment on which is best to
use when running in high speeds. I was taught awhile back ago to use the
10% - 90%, but am running allot of info that using the 20% - 80% is more
accurate.
Thanks to all who reply,
Rich
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