[SI-LIST] Re: Long T reflection problems
- From: "Grasso, Charles" <Charles.Grasso@xxxxxxxxxxxx>
- To: "'McKinley, Jory D'" <jory.d.mckinley@xxxxxxxxx>, "'james.stein@xxxxxxxxxxxxxx'" <james.stein@xxxxxxxxxxxxxx>, "'si-list@xxxxxxxxxxxxx'" <si-list@xxxxxxxxxxxxx>
- Date: Wed, 2 Mar 2005 13:12:57 -0700
Thanks - I quickly scanned the email and missed that.
But in rereading the email I find:
"dt_r/dt/f of approx. 0.3 to 0.5 ns" I have no
idea what this means!
Best Regards
Charles Grasso
Senior Compliance Engineer
Echostar Communications Corp.
Tel: 303-706-5467
Fax: 303-799-6222
Cell: 303-204-2974
Pager/Short Message: 3032042974@xxxxxxxx
Email: charles.grasso@xxxxxxxxxxxx;
Email Alternate: chasgrasso@xxxxxxxx
-----Original Message-----
From: McKinley, Jory D [mailto:jory.d.mckinley@xxxxxxxxx]
Sent: Wednesday, March 02, 2005 12:06 PM
To: Grasso, Charles; james.stein@xxxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: RE: [SI-LIST] Re: Long T reflection problems
Remember it's not the frequency but the edge rate and at 300ps worst case
and assuming 180ps/in the full wavelength is roughly 150mm. This will
reflect off the OC.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Grasso, Charles
Sent: Wednesday, March 02, 2005 1:37 PM
To: 'james.stein@xxxxxxxxxxxxxx'; 'si-list@xxxxxxxxxxxxx'
Subject: [SI-LIST] Re: Long T reflection problems
If the frequency is really about 2MHz (or a wavelength
of about 500 feet ) then I anticipate you
won't have much of an SI problem!
Best Regards
Charles Grasso
Senior Compliance Engineer
Echostar Communications Corp.
Tel: 303-706-5467
Fax: 303-799-6222
Cell: 303-204-2974
Pager/Short Message: 3032042974@xxxxxxxx
Email: charles.grasso@xxxxxxxxxxxx;
Email Alternate: chasgrasso@xxxxxxxx
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On
Behalf Of Stein, James F (UK)
Sent: Wednesday, March 02, 2005 8:00 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Long T reflection problems
Hi Everyone,
I have question about signal reflections, I have added some specific data=
but rule of thumb answers are all welcome as i'm new to SI! I have a
bi-directional signal that is loaded with an LV-CMOS transceiver= at 5pF on
each end and a dt_r/dt/f of approx. 0.3 to 0.5 ns. The frequency of data
across this is about 2 MHz. The= distance between the two buffers is about
15mm.=0D This signal needs to be observed externally with a logic analyser
for test= purposes.=0D The track between the two transceivers is t'd to a
test connector giving a= t'd track length of about 150mm.=0D In normal
operation the analyser would not be connected so the long track= section is
o/c; when connected to an analyser then you could probably add a metre to
the total track length.
In this case, what sort of SI problems would I expect to see, both with the=
track o/c and also plugged into an analyser? Would series termination be
sufficient to prevent reflections, or should= the test signal go through a
buffer (last resort really) before the test connector?
Regards
James
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