Subject: BIRD9.1 TERMINATORS

From: [email-masked] ( Bob Ross)
Date: Mon, 21 Feb 94 16:03:22 PST

Hello IBIS members:

Based on the brief discussion and recommendations at the 2/18/94 forum,
BIRD9.1 is issued as a more robust terminator proposal with the additional
capability of handling RC terminators and internal Series terminators.

Packages containing resistor arrays or RC arrays are used in digital circuit
design.  It is reasonable to include IBIS formatting capablility so these
elements can be entered into the database.  Without such capability, the
user must enter these components through individual, simulator-specific
constructs.  Forcing a mixed input format is undesireable.

For many terminators, the POWER and GND pin attachments are left to the
user.  For example, a resistor array could be used for pullup attachments
in an open_drain or as a terminator to ground.  So the user is expected to
provide most of the [Model]s based on the connection configuration.

Bob Ross, Interconnectix, Inc.

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                 Buffer Issue Resolution Document  (BIRD)

BIRD ID#:                9.1
ISSUE TITLE:             Terminator Specification 
REQUESTOR:               Bob Ross, Interconnectix, Inc. 
DATE SUBMITTED:          2 February 1994
DATE REVISED:            21 February 1994
DATE ACCEPTED BY IBIS OPEN FORUM:     {will be filled in when accepted}

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STATEMENT OF THE ISSUE:  

  Terminators are used in design and can exist as packaged parts.  Therefore
they are candidates for IBIS modeling.  

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STATEMENT OF THE RESOLVED SPECIFICATIONS:  

  The additional keywords, [Rpower] and [Rgnd], are proposed to represent
resistors connected to power (VCC) and ground (GND) or to the voltages based
on the voltage reference rules in BIRD3 as they apply to [POWER_clamp] and
[GND_clamp].  A series terminator keyword [Rseries] is proposed.  Finally,
and AC terminator requiring both [Rac] and [Cac] to GND is proposed.

|==============================================================================
|    Keywords:  [Rgnd], [Rpower], [Rac], [Cac], [Rseries]        
|    Required:  Yes, if they exist in the device                              
| Description:  The data for these keywords define the resistance values of
|               Rgnd and Rpower connected to GND and the POWER pins,           
|               respectively.                                                 
| Usage Rules:  For each of these sections the three columns hold the         
|               typical, minimum, and maximum resistance values.  The three  
|               entries for R(typ), R(min), and R(max) or C(typ), C(min),
|               and C(max) must be placed on a single line and must be    
|               separated by at least one white space or tab character.       
|               All three columns are required under these keywords, however  
|               data is only required in the typical column.  If minimum      
|               and/or maximum values are not available, the reserved word
|               "NA" must be used indicating the R(typ) or C(typ) value by
|               default.  
| Other Notes:  It should be noted that [Rpower] is connected to 'Vcc' and      
|               [Rgnd] is connected to 'GND'.  However, [GND_clamp reference] 
|               voltages, if defined, apply to [Rgnd].  [POWER_clamp reference]
|               voltages,  if defined, apply to [Rpower].                                                 |               Either or both [Rgnd] and [Rpower] may be defined and may
|               co-exist with [GND_clamp], [POWER_clamp], [Pulldown], and
|               [Pullup] structures.
|               If an AC terminator is specified, then both [Rac] and [Cac]
|               are required.
|------------------------------------------------------------------------------
| variable      R(typ)          R(min)          R(max)
|
[Rgnd]          330Ohm          300Ohm          360Ohm   | Parallel Terminator
[Rpower]        220Ohm          200Ohm          NA       |
|
[Rseries]        10Ohm          NA              NA       | Series terminator
|
[Rac]            30Ohm          NA              NA       | 
|                                                        |
| variable      C(typ)          C(min)          C(max)   | AC terminator
|                                                        |
[Cac]            50pF            NA             NA       | 
|==============================================================================

  The "Other Notes:" text within the [Model] Keyword description is changed
to include references to the new keywords:

| Other Notes:  A complete [Model] description normally contains the following 
|               keywords:  [Voltage range], [Pullup], [Pulldown], [GND_clamp], 
|               [POWER_clamp], [Rgnd], [Rpower], [Rseries], [Rac], [Cac],
|               and [Ramp].  However, some models may have only 
|               a subset these keywords.  For example, an input structure      
|               normally only needs the [Voltage range], [GND_clamp], and      
|               possibly the [POWER_clamp] keywords.                           
|               Note that C_comp defines the silicon die capacitance.  This    
|               value should not include the capacitance of the package.      
|                                                                             
|------------------------------------------------------------------------------

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ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:  

  A set of terminator components is useful to be formatted using IBIS because
they are found as packaged components.  All of the options can support (typ),
(min) and (max) specifications.

(1) Parallel Resistor Termination:

  The additonal elements [Rpower] and [Rgnd] provide terminations to Vcc, Gnd
or both.  Devices such as the Motorola MCC142233 to MCC142236 Switchable SCSI
Passive Bus Terminator series would be modeled with these elements. 

  At least two other techniques could be used in IBIS Version 1.1.  The 
[POWER_clamp] or [GND_clamp] tables could be used (with as few as two data
points each) to represent resistors.  Another method could be to use R_pkg
(or R_pin) with [POWER_clamp] or [GND_clamp] structures configured as a 
very low impedance.  Processing tabular data for these purposes would be less
efficient and less obvious than working with resistive elements directly.  

(2) RC (or AC) Termination:

  R_pkg (or R_pin) and C_comp can provide RC terminations.  This proposal
specifies [Rac] connected to [Cac] elements.  This will allow packaged RC
terminations which include built in clamping diodes to be modeled directly.

(3) Internal Series Resistance Terminations:

  R_pkg (or R_pin) can be used to model internal series terminations.  This
proposal specifies an internal [Rseries] component.  It is structured so that
it would be added to the already existing R_pkg element.

  Diode terminators already can be modeled using IBIS Version 1.1:

(4) Diode Termination:

  Devices such as the TI SN74S1050 thru SN74S1056 Schottky Barrier Diode
Bus-Termination Arrays can be modeled using existing [POWER_clamp] and
[GND_clamp] structures.  

  The total context model is attached showing the proposed additons.  BIRD9.1
expands BIRD9 by adding the RAC, CAC, and RSERIES elements

 |<------------------------OUTPUT and I/O Models--------------------------->|
                                                                            |
                        |<-------------------INPUT Model------------------->|

    VOLTAGE RANGE or       VOLTAGE RANGE or
       PULLUP REF           POWER_CLAMP REF
           o                       o
           |                       |
      |----o----|       POWER_ |---o---|
      |         |       CLAMP  |       |
   |--o--|   |--o--|        |--o--|    \
   |     |   |     |        |     |    /
 |-|RAMP |---| VI  |--|     | VI  |    \ RPOWER            PACKAGE Keyword
 | |     |   |     |  |     |     |    /                      Parameters
 | |-----|   |-----|  |     |--o--|    |                |<----------------->|
 | dV/dt_r   PULLUP   |        |       |            
 |                    |        |       |                                     PIN
 |                    |--o-----o-------o-----o---/\/\/\--/\/\/\--UUUUUU---o--o 
 |                    |  |     |GND_   |     |   RSERIES  R_PKG   L_PKG   |
 | dV/dt_f   PULLDOWN |  |     |CLAMP  |     |                            |
 | |-----|   |-----|  |  |  |--o--|    |     |                            |
 | |     |   |     |  |  |  |     |    \     |                            |
 |-|RAMP |---| VI  |--|  |  | VI  |    /RGND |                            |
   |     |   |     |     |  |     |    \     \                            |
   |--o--|   |--o--|     |  |--o--|    /     / RAC                        | 
      |         |        |     |       |     \                            |
      |----o----|        |     |---o---|     /                            |
           |             |         |         |                            |
           o     C_COMP ---        o        --- CAC                C_PKG ---
        GND or          ---     GND or      ---                          ---
     PULLDOWN REF        |   GND_CLAMP REF   |                            |
                         |                   |                            |
                         |-------------------o----------------------------|
                                             |
                                             o
                                            GND

                                      |<-------------->|
                                           Proposed 
                                          Terminator
                                           Keywords

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ANY OTHER BACKGROUND INFORMATION:

This BIRD partially addresses the issue related to BIRD2 regarding 
Termination Resistor Packs and Termination Diode Packs.  It does not
address Discrete two-port devices except through one partial solution
with internal series terminators.

The adoption of this BIRD would require some text changes in BIRD3 to 
reference the new keywords.

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