[SI-LIST] Re: Basic IBIS I/V curve question
- From: Gustavo Blando <gblando@xxxxxxxxxxxx>
- To: "'marko.pulli@xxxxxxxxx'" <marko.pulli@xxxxxxxxx>,Andrew.Ingraham@xxxxxx
- Date: Thu, 7 Nov 2002 10:41:15 -0500
I am confused here. I though that even though the curves are VCC relative on
IBIS
it does matter the voltage at which the VI curves where extracted.
If you go and change the voltage range on the model, Yes the IV curve will
now be referenced to a different voltage, but that does not mean necesarely
that the IV
curve is correct now.
Changing the voltage as Andrew said, "depending on the driver" will change
the characteristics of the drive strength.
Thanks.
Gus.
-----Original Message-----
From: marko.pulli@xxxxxxxxx [mailto:marko.pulli@xxxxxxxxx]
Sent: Thursday, November 07, 2002 10:01 AM
To: Andrew.Ingraham@xxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Basic IBIS I/V curve question
Hi,
I was misled by one thing in my simulator.
You are absolutely right that the curves are independent of min/max =
voltage.
It looks like the simulator always uses the min and max from what is =
defined in the IBIS model [Voltage range] line.
I was trying to set the minimum and maximum voltage in the simulator =
environment but it doesn't seem to work.
Now I have changed the [Voltage range] section in the model itself to =
correspond the actual min and max in my design..
Thanks for guiding me back into the right path!
Br,
Marko
> -----Original Message-----
> From: ext Ingraham, Andrew [mailto:Andrew.Ingraham@xxxxxx]
> Sent: 07. November 2002 14:52
> To: si-list@xxxxxxxxxxxxx; Pulli Marko (NET/Espoo)
> Subject: [SI-LIST] Re: Basic IBIS I/V curve question
>=20
>=20
> Ideally, the three I-V curves would be independent of the operating
> supply voltage. The curves are Vcc-relative, so each of the three
> curves could be used with any supply voltage within the=20
> normal operating
> range.
>=20
> The minimum I-V curve is supposed to represent slow/weak=20
> silicon (due to
> IC processing variations) at whatever temperature results in slow/weak
> operation (high temp. for MOS, low temp. for bipolar). Since=20
> the supply
> voltage typically does influence device drive strength and speed, the
> minimum I-V curve is usually extracted when the supply voltage is also
> at minimum.
>=20
> I don't know how you can tell that the minimum I-V curve=20
> corresponds to
> any operating voltage. It shouldn't have any clues about the=20
> operating
> voltage.
>=20
> If you question whether the minimum I-V curve is valid, you should
> discuss this with the IC vendor or whoever made the IBIS=20
> model. Without
> that discussion, one should assume that the minimum I-V curve truly
> represents a worst-case device.
>=20
> Regards,
> Andy
>=20
>=20
>=20
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>=20
>=20
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