RE: [IBIS-Users] 3.3V I/O, 5V tolerant

From: Lynne D. Green <lgreen22_at_.....> Date: Sun Dec 18 2005 - 15:16:54 PST · This archive was generated by hypermail 2.1.8 : Sun Dec 18 2005 - 15:21:56 PST

Hello Abril,

Please consider using s2ibis3, since s2ibis3 fixed many of the algorithm and
coding problems in s2ibis2.

If your core voltage has corners, you will need to determine the best and
worst simulation corners (combinations of Vcc and Vcore).

In s2ibis2 and s2ibis3, you must manually edit the spice files.
* run s2ibis2/s2ibis3 to create the SPICE files, setting voltage range for
-Vcc to 2*Vtolerant (this sets the range of simulation and model tables)
* connect normal core voltage to the I/O buffer (2.5V) for every file
* connect normal Vcc to the I/O buffer (3.3V) for every file
* run the SPICE simulations
* run the extraction half of s2ibis2/s2ibis3.
The s2ibis2/s2ibis3 documentation describes how to finish running
s2ibis2/s2ibis3 after editing the SPICE files.

If you are planning to do this more than once, you might consider writing a
script.  If you are really lucky, someone will share a script they have
written.

Best regards,
Lynne

"IBIS training when you need it, where you need it."

Dr. Lynne Green
Green Streak Programs
http://www.greenstreakprograms.com
425-788-0412
lgreen22@mindspring.com

-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf
Of Abril, Giovanni (Space Technology)
Sent: Sunday, December 18, 2005 9:53 AM
To: tom@teraspeed.com; ibis-users@eda.org
Subject: RE: [IBIS-Users] 3.3V I/O, 5V tolerant

Thanks for your response Tom.

The part has a 2.5V core and 3.3V i/o voltage.  Changing the voltage
reference, would mean my 3.3V rail gets set to 5V.  Is that how it should be
done?  Also, I think s2ibis ignores my rising/falling waveform fixture
values (of 3.3, 3.0, 3.6) and sets them to 5.0, 4.5, and 5.5V.

-----Original Message-----
From: Tom Dagostino [mailto:tom@teraspeed.com]
Sent: Saturday, December 17, 2005 4:53 PM
To: Abril, Giovanni (Space Technology); ibis-users@eda.org
Subject: RE: [IBIS-Users] 3.3V I/O, 5V tolerant

I'd change it to:

Voltage Ref: 5.0 4.5 5.5
Pulldown Ref: 0 0 0
Pullup Ref: 3.3 3.0 3.6
Power Clamp Ref: 5.0 4.5 5.5
GND Clamp Ref: 0 0 0

Tom Dagostino
Teraspeed(R) Labs
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065
tom@teraspeed.com
www.teraspeed.com

Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
401-284-1827

-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org]On
Behalf Of Abril, Giovanni (Space Technology)
Sent: Saturday, December 17, 2005 12:54 PM
To: ibis-users@eda.org
Subject: [IBIS-Users] 3.3V I/O, 5V tolerant

Hello IBIS experts,

I'm creating a model from HSPICE using S2IBIS2 vers. 2.1 and have a
question.

If my buffer is 3.3V i/o, but is 5V tolerant, and am using:

Voltage Ref: 3.3 3.0 3.6
Pulldown Ref: 5.0 4.5 5.5
Pullup Ref: 0 0 0
Power Clamp Ref: 5.0 4.5 5.5
GND Clamp Ref: 0 0 0

I was thinking this should vary my voltages from -5V to 10V for the clamps,
but it does not.  It instead varies from -Vcc to 2Vcc as usual.

Is this how I should be setting this up?

Thanks,
Gio

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