[SI-LIST] Re: ac drive strength
- From: "Muranyi, Arpad" <arpad.muranyi@xxxxxxxxx>
- To: "'si-list@xxxxxxxxxxxxx'" <si-list@xxxxxxxxxxxxx>
- Date: Thu, 26 Jul 2001 11:56:42 -0700
Chuck,
I disagree, testing the characteristics of a buffer is
best done with a resistive load (or a long transmission
line). Measuring the voltage swing tells you how
strong the buffer is, and measuring the time it took
to do that swing is telling you how fast the buffer
is. The 20-80% of these are the dV and dt numbers
IBIS uses also.
If you load the driver with a capacitor you mix the
strength and speed into one number, and you will not
be able to distinguish between strength and speed.
The same goes for dividing dV/dt into a slope.
Arpad Muranyi
Intel Corporation
========================================================
-----Original Message-----
From: Chuck Hill [mailto:chuckh@xxxxxxxxxxx]
Sent: Monday, July 23, 2001 10:49 AM
To: si-list@xxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: ac drive strength
You could try measuring risetime into a capacitive load. This is
essentially dv/dt into C and measures the current drive of the
buffer. Measure this at several different capacitive loads. Plot the
points and see if the current source is a good model for your buffer. If
the risetime doesn't change much over a range of capacitive loads, then
your buffer is better modeled by a voltage source.
Watch out for stray inductance in your test setup.
Chuck Hill, consultant
At 11:30 AM 7/23/01, Peterson, James F (FL51) wrote:
>Hello,
>
>What's the best way to specify the ac drive strength of a buffer? The
>requirement should be testable.
>
>I was thinking about defining it with a source impedance at typical
>voltage/temp's....any suggestions on how to test this?
>
>thanks,
>Jim
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