[SI-LIST] Re: About the Cref in IBIS Model
- From: james.f.peterson@xxxxxxxxxxxxx
- To: yinko_cheng@xxxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Wed, 4 Jun 2003 04:12:44 -0700
Yinko,
I believe the model was made incorrectly. The "test" waveform (based on
either a dv/dt number or a V/T curve), should have had a load that =
matched
the data sheet - which in this case would have included a Cref of 50pf. =
If
it doesn't, then the timing analysis will be inaccurate. It should show =
a
longer delay (because of the double dipping effect of the timing in the =
data
sheet with a 50pf load and the timing in the SI analysis). A longer =
delay is
more conservative when looking at setup timing, but is less =
conservative and
a problem when looking at hold times. In other words, it can be telling =
you
that your hold time is good when it's really not.
call your model maker and ask them to fix the problem.
Jim Peterson
Honeywell
-----Original Message-----
From: cheng yin [mailto:yinko_cheng@xxxxxxxxxxx]
Sent: Tuesday, June 03, 2003 9:04 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] About the Cref in IBIS Model
Hi,
I got a IBIS Model file from the device producer.=20
I find this text in one output model : Rref =3D 500ohms . and no =
Cref=20
here.
But in the DataSheet of this device, it told me the t_pd measurement=20
information is
RL =3D 500ohms to GND, CL =3D 50pf to GND .
I want to caculate the propogation delay and final settle delay of this =
device. I'm using
cadence's SpecctraQuest tool. So I think I should add 'Cref =3D 50pf' =
to the=20
IBIS file. Am I right?
Who can tell me how to do it?
thanks
Yinko
_________________________________________________________________
=C3=E2=B7=D1=CF=C2=D4=D8 MSN Explorer: http://explorer.msn.com/lccn/ =
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