Bird 13, Measurement condition clarification

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                   Buffer Issue Resolution Document (BIRD)

BIRD ID#: 13.0
ISSUE TITLE: Clarify Some Conditions of Measurements
REQUESTOR: Bob Ward, Texas Instruments

DATE SUBMITTED: April 22, 1994
DATE REVISED:
DATE ACCEPTED BY IBIS OPEN FORUM: pending

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STATEMENT OF THE ISSUE:

Certain statements are made in the Version 1.1 standard that need clarification
for the sake of newcomers to the Ibis community regarding the conditions under
measured data is taken. These changes bring the standard more into line with
the discussions on the forum and the cookbook, which is taken to reflect the
intention and not just the letter of the specification.

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STATEMENT OF THE RESOLVED SPECIFICATIONS:

The majority of the change is to the NOTES TO DATA DERIVATION METHOD section of
the spec.

In paragraph numbered 1)

Old text is:
| V/I Curves for CMOS devices:
| typ = nominal voltage, 50 degrees C, typical process
| min = low voltage tol, 100 degrees C, typical process, minus "X%"
| max = hi voltage tol, 0 degrees C, typical process, plus "X%"
|
| V/I curves for bipolar devices:
| typ = nominal voltage, 50 degrees C, typical process
| min = low voltage tol, 0 degrees C, typical process, minus "X%"
| max = hi voltage tol, 100 degrees C, typical process, plus "X%"

Proposed text is:
| V/I Curves for CMOS devices:
| typ = nominal voltage, nominal temperature deg C, typical process
| min = low voltage tol, max temperature deg C, typical process, minus"X%"
| max = hi voltage tol, min temperature deg C, typical process, plus
"X%" |
| V/I curves for bipolar devices:
| typ = nominal voltage, nominal temperature deg C, typical process
| min = low voltage tol, max temperature deg C, typical process, minus "X%"
| max = hi voltage tol, min temperature deg C, typical process, plus "X%"
|
| where nominal, min, and max temperature are specified by the manufacturer
| of the part. The preferred range is 50C nom, 0C min and 100C max
| temperatures.

Add after the end of paragraph numbered 2) and before 3):

These voltage ranges apply to simulation derived data. Data derived from lab
measurements should be taken as near to this range as equipment will allow (
e.g. a curve tracer may limit current to nondestructive values even at these
voltage extremes ) or as limited by manufacturer specified absolute maximum
voltages.

Add in paragraph numbered 3) after step 3 and before step 4 the following note:

There may be devices which will not drive a load of only 50 ohms
into any useful level of dynamics. In these cases use the manufacturers
suggested ( non-reactive ) load and add the load sub parameter to the [Ramp]
specification.

Under the heading Ramp times for CMOS devices, make the same temperature
specifications as above.

Add a note after step 7. in the same section that during the ramp measurements
the driving waveform should be of a rise/fall time typical of the actual circuit
in operation. Also the driving waveform should not have sharp breakpoints at
the top and bottom of the edges, but should be slightly rounded to avoid
artificial high frequency effects.

Add specification of the sub parameter 'load' to the [Ramp] keyword. Under
Keyword: [Ramp]
change Sub-Params: dV/dt_r, dV/dt_f, load

Add text to the Usage Rules:
The load sub-parameter is optional if the preferred 50 ohm load is used. It is
required if a non-standard load is used.

Add to the example as follows:
[Ramp]
| variable typ min max
dV/dt_r 4.2/1.8n 3.5/2.5n 5.0/1.1n
dV/dt_f 2.5/1.5n 2.0/2.3n 3.0/0.8n
load 300ohms

Add after the [Voltage range] keyword discussion:

|==============================================================================
|
| Keyword: [Temperature range]
|
| Required: Yes, if other than the preferred 0, 50, 100 degree C range
|
| Description: Used to define the temperature range over which the model is
| to operate.
|
| Usage Rules: Actual temperatures (not percentages) are to be presented in
| the usual typ, min, max format. "NA" is not allowed.
|
| Other Notes: [Temperature range] also describes the temperature range over
| which the various V/I curves and ramp rates were derived.
|------------------------------------------------------------------------------
| variable typ min max
[Temperature range] 27.0C -50C 130.0C

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ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:

{There are many "experts" reviewing this document. Your reasons,
analysis, and justifications must be precise and well documented, or your BIRD
will be sent back to you. Use this section to show that you've done your
homework, and answer all questions that will undoubtedly be asked. If your
issue is a change instead of an enhancement, document how backward compatibility
is to be addressed.}

The spec should have flexibility enough to handle models of parts manufactured
to MIL spec and automotive spec as well as parts for special purposes which are
perhaps more sensitive than even consumer or commercial spec allows. Thus the
relaxation , or tightening as the case may be, of the temperature and voltage
range mandates.
The added keyword and sub-parameter are to allow the simulator usable
specification of the relaxed or tightened ranges for the relevant measurements.

The ramp rate is still mandated to be determined between 20 and 80 % of actual
swing to promote the linearity of the measured portion
of the edge. The load is mandated to be non-reactive so as to preserve the
inherent dynamics of the driver, and not introduce false dynamics due to the
load.

Backward compatibility is addressed by making the new specifications optional if
the preferred voltage and temperature ranges and load resistance are used.

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ANY OTHER BACKGROUND INFORMATION:

N/A

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Received on Wed Apr 27 17:42:19 1994