Subject: I/O buffer modeling cookbook
From: Yoked Erlich (r58559) (r58559@email.sps.mot.com)
Date: Sun Aug 12 2001 - 04:18:21 PDT
Hi ,
I would like to ask some questions about the 'I/O buffer modeling
cookbook'
paper (revision 2.0X) , Which I've got from 'www.eig.org' web site.
1. Is there anywhere I can find revision 3.2 cookbook?
2. I've an I/O buffer model which working in some chip pads as I/O ,
some pads as steady input and some pads as steady output.
I would like to know if the buffer grouping is made by the buffer
type or by the pad direction?
If buffer type is the answer so one model with I/O type in enough
for this buffer,
If pad direction is the answer so three model is needed for this
buffer , I/O model , Input model and Output model
( in this case Input and Output model tests will be exactly the same
as I/O model ) .
3-6 questions are about 'Extracting Data for the [Ramp] keyword'
paragraph in the cookbook :
3. It is written that 'if the device does not have enough
drive capability to make a significant output transition than a
higher load may be used' ,
How much is significant output transition ?
4. it is written that ' For an open drain , measure the rise and fall
time into the load resistor and voltage used
by the manufacture when specifying propagation delays' , This
sentence is not clear
what is the test structure in open drain buffer case?.
5. it is written that ' Falling edge ramp data is captured with the load
resistor tied to VCC'
, Is VCC mean the pmos Driver source voltage (pad voltage) or low
voltage?
6. It is written that 'simulations are performed with C_comp included in
the circuit' , This sentence is not clear.
As I understood C_comp is the capacitance seen when looking from the
pad back into the buffer ,
It is written that C_comp should be added to the simulation , but
C_comp is not a capacitor it is capacitance measurement.
7. In 'Ground Clamp' paragraph it is written that 'The data in table
must cover the range of -Vcc to Vcc ' ,
Isn't it suppose to be -Vcc to 2*Vcc ?
8. In 'pulldn' paragraph it is written 'If the buffer is a 3-state
device then first subtract the ground clamp current
from the pulldown current then enter the result into the [pulldown]
table' ,
first , it is written above the graph 'Pullup I/V curve after
subtraction of ground clamp currents' Which is probably mistake.
second , Should I replace the pulldn results in Ibis model file
after the subtraction?
9. In 'Power Clamp' It is written that 'the data in the table must cover
the range of vcc to vcc*2' ,
Isn't the range suppose to be -Vcc to 2*Vcc ?
--With regards,
Yoked.
_____________________________________ E-mail: yokede@msil.sps.mot.com Tel: 972-9-9522482 Fax: 972-9-9522888 WIRELESS CIRCUIT - IO GROUP MOTOROLA SEMICONDUCTOR ISRAEL
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