RE: Clarification needed.

Adam, Anbazhagan:

 Hi. The output impedance of an I/O buffer is contained directly in the I/V
curves of the pullup and pulldown. Add to this the package parasitics and
you should have the impedance of the I/O buffer looking back through the
package.

Regards,

Matt

-----Original Message-----
From: Adam.Tambone@fairchildsemi.com
[mailto:Adam.Tambone@fairchildsemi.com]
Sent: Thursday, May 24, 2001 9:16 AM
To: ibis@eda.org; ibis-users@eda.org
Subject: Re: Clarification needed.

Anbazhagan,

Sounds good to me... I haven't modeled a ASIC but you seem to be on the
right track.

Regarding point 3. I'm not sure how the output impedance of the I/O buffer
can be included in a IBIS datasheet so this is probably not necessary.
Others with more experience may correct me on this.

Regarding point 5. the DC sweep for I/V data is -Vcc to 2Vcc, so in your
case this seems to be -3.3V to 6.6V. Do not forget that Pullup data has a
domain of Vtable=Vcc - Vin, where Vin is the DC voltage sweep.

For a I/O buffer here are the parameters and data you will want to form a
IBIS model, you have already described most of these:

     Polarity
     Vref, Rref, Cref
     Ccomp
     Temperature Range
     Voltage Range
     Pulldown Data
     Pullup Data
     Rising and Falling Waveforms across the Voltage Range, one set at 50
Ohms to gnd, another set at 50 Ohms to Vcc ( assuming the ASIC is CMOS )
     Ramp Data

     additionally you will want the R L C packaging parameters either pin
specific or general typ, min, max values
     you would also want the I/V curves for the Power and GND Clamps but
you have stated that these do not exist

Refer to the 3.2 spec for definitions and descriptions of the above data
and parameters.

One other point, when requesting this data be sure to mention you want no
more than 100 points per data curve.

Hope this is of some help.

Adam Tambone

Anbu@scmmicro.co.in on 05/24/2001 02:48:13 AM

To: "ibis-users@eda.org":@server.eda.org
cc:

Subject: Clarification needed.

Hello Users,

        I am using XTK to simulate a PCBA. The board has a 100pin ASIC. In
order to model the ASIC properly I need the IBIS model of the ASIC which I
can convert it to XTK format. Now if I directly request for an IBIS model
the vendor may hesistate. So I am requesting the following data from the
vendor with which I can create a IBIS model. Below is the data I am
requesting them. Is it OK. Does it cover everything necessary to create a
proper IBIS model?. The ASIC does not have any clamp diodes. Please reply.
The following data whichever is applicable for each pin of the ASIC are
needed
 1. Package parasitics namely, the Resistance, capacitance and Inductance.
Typical, max, min values required.

2. Die capacitance as seen at the die pad. Typical, max, min values
required

3. Output impedance of the I/O buffers. Typical, max, min values required.

4. Rise time and fall time values (dv/dt typical, max, min) of buffers
excluding the effect of packaging but including the effect of die
capacitance. Load conditions required.

6. Rising edge and falling edge waveforms (Voltage vs. time curve with the
voltage values having typical, max, min values) of the driver along with
the test conditions.

5. V/I characteristics of Pull up and Pull down resistor, if present, when
the buffer is driven high and low respectively. The voltage sweep must be
from ?3.3V to +6.6V. Current measurement with typical, max, min values are
required.

Thanks,

Anbazhagan.

 
Received on Thu May 24 06:29:33 2001