Subject: Re: [IBIS-Users] Waveform mismatch question
From: John Phillippe (john.phillippe@motorola.com)
Date: Fri Jan 24 2003 - 09:19:29 PST
Duane Mattheisen wrote:
> John Take out as much fixture resistance as possible in the DC
> measurement.
> Also for the AC measurement put a big capacitor (0.1uf and a >2.2uF
> tantalum cap) to ground on the Rfixture having the other side of the
> Rfixture that connects to the output as close as possible to the
> output.
> Sincerely Duane Mattheisen
> "Angulo, John" wrote:
>
>>The following is posted on behalf of John Phillippe at Motorola. Please send any private replies to john.phillippe@motorola.com only.
>>
>>--------------------------------------------------
>>
>>Ibis Guru's,
>> I get quite a few waveform mismatches between the rising/falling
>>edges and the I/V curves like the one shown below.
>>
>>WARNING - Model pad_26v_fast: The [Falling Waveform]
>> with [R_fixture]=50 Ohms and [V_fixture_max]=0V
>> has MAX column DC endpoints of 0.05V and 1.75v, but
>> an equivalent load applied to the model's I-V tables yields
>> different voltages ( 0.16V and 1.91V),
>> a difference of 6.66% and 8.94%, respectively.
>>
>>I'm curious if this is a common problem, or if there are some simple
>>solutions to get everything to match up. I check the waveforms and set
>>the sim time long enough to make sure the waveforms are stable. Any
>>help/suggestions would be greatly appreciated.
Duane,
Since I'm using s2ibis2, I should make rload as small as possible?
On the order of 1ohm? I read in this group before to use an rload of
50ohms since that is what most people are using, and that it is a bit of
a "standard." I've also been told to have NO capacitance in the AC
measurements, and again to only use a 50ohm resistor.
I did try a run with a 0.1uF cap on the pad for the AC measurements,
but that just slows the edge down.
-- John Phillippe SPS, 32 Bit Embedded Controller Division, IC Creation Motorola - 512-895-1835 Austin, TX - john.phillippe@motorola.com|------------------------------------------------------------------ |For help or to subscribe/unsubscribe, email majordomo@eda.org |with just the appropriate command message(s) in the body: | | help | subscribe ibis <optional e-mail address, if different> | subscribe ibis-users <optional e-mail address, if different> | unsubscribe ibis <optional e-mail address, if different> | unsubscribe ibis-users <optional e-mail address, if different> | |or email a written request to ibis-request@eda.org. | |IBIS reflector archives exist under: | | http://www.eda.org/pub/ibis/email_archive/ Recent | http://www.eda.org/pub/ibis/users_archive/ Recent | http://www.eda.org/pub/ibis/email/ E-mail since 1993
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