[SI-LIST] Re: How to improve non monotonic
- From: "Tom Dagostino" <tom@xxxxxxxxxxxxx>
- To: "'Lockard, Nickolaus J.'" <Nickolaus.Lockard@xxxxxxx>, "'Carrier, Patrick'" <Patrick_Carrier@xxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Thu, 14 Jan 2010 11:48:20 -0800
8 pF sounds awful high for an input Cin. It may be in the datasheet but
unless you are using really old technology it is way out of line. It is
more likely to be on the order of 2 pF or less depending on the package.
Tom Dagostino
Teraspeed(R) Labs
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065
503-430-1285 FAX
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 Lockard, Nickolaus J.
Sent: Thursday, January 14, 2010 10:53 AM
To: Carrier, Patrick; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: How to improve non monotonic
Hello, thanks for the replies. This is a Slow-Weak simulation in
HyperLynx, being probed at the receiver. However, I do not have an IBIS
model for the receiver, so I am using an 8pF cap, which is the Cin for
the receiver. I suppose these curves are due to the cap instead of
having a proper receiver???
So, is there no general methodology for reducing these kinds of
problems?
Thanks again,
-NL
-----Original Message-----
From: Carrier, Patrick [mailto:Patrick_Carrier@xxxxxxxxxx]
Sent: Thursday, January 14, 2010 1:33 PM
To: Lockard, Nickolaus J.; si-list@xxxxxxxxxxxxx
Subject: RE: [SI-LIST] How to improve non monotonic
Hi Nick--
Usually, termination works best. In the case you describe below, with
your series termination, it sounds like you should have nice clean
edges. Some ideas as to why you might be seeing the glitch:
If this is in a simulation:
1. Make sure you are looking at the receiver signal
2. Make sure your IBIS model waveforms for the driver look good
3. Make sure you are using an LVCMOS or similar input impedance receiver
Or if this is a lab measurement:
1. Make sure you are looking at the receiver signal
2. When measuring, make sure you are using a high bandwidth,
high-impedance probe, that is connected close to the receiver without
any large wires on the signal probe or the reference connection
3. If you are doing all that, this glitch could also be crosstalk or
ground bounce, so you may want to look into that as well
--Pat
Patrick Carrier
Technical Marketing Engineer
High Speed Design
Mentor Graphics Corporation
Patrick_Carrier@xxxxxxxxxx
ph. (512) 425-3015
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Lockard, Nickolaus J.
Sent: Thursday, January 14, 2010 12:00 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] How to improve non monotonic
Hello,
In general, how can one improve the quality of an LVCMOS clock signal
that has a non-monotonic trailing edge?
The circuit is an LVCMOS driver, 25MHz, 3.3V, with a series 33.2 ohm
resistor at the driver, 50 ohm trace, 4 inches. The problem is the
trailing edge of the clock starts to rise back up and approach the
allowable threshold before it begins to fall back to 0V. How can this
rise be dampened, or eliminated?
Thanks,
NL
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List technical documents are available at:
http://www.si-list.net
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List technical documents are available at:
http://www.si-list.net
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List technical documents are available at:
http://www.si-list.net
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
