[IBIS] BIRD95.4: Power Integrity Analysis using IBIS

From: Syed Huq <shuq_at_.....>
Date: Tue Apr 19 2005 - 18:35:56 PDT
To All:

BIRD95.4 removes the proposed set of [*_Equiv] keywords since the same
additions can be accomplished with the existing set of passive Series
keyword.  The difference is that the Series keywords are for all the
buffers on the bus, whereas the [*_Equiv] keywords were for individual
buffers.

The limitations regarding Input and Terminator buffers are removed
for impedance paths between power and ground.  The Series keywords
can also be used to document such paths, as needed.

BIRD95.4 also adds some details regarding the other rails in the model.
It also clarifies some ambiguous language regarding ECL technnology.

BIRD95.4 DOES NOT discuss algorithms to process the additional
information. However the algorithm is expected to be one in which
"difference" current sources are added to the reference buffer model in
order to reproduce the extracted [Composite Current] I-T tables under
the several test conditions (or at least provide a close
approximation).  The EDA algorithms are expected to take into account
existing elements in the model and to adjust currents properly to avoid
double counting.

The proposed BIRD97 give more adjustments for rail collapse and does
not dependent on the BIRD95.4 content.

Some discussion of changes is given in the ANALYSIS PATH/DATA THAT LED
TO SPECIFICATION: section under BIRD95.4.

BIRD95.4 will be discussed in the Fri April 22nd IBIS Teleconference.

Syed Huq

-- 
Cisco Systems, Inc
Acting Chair - EIA IBIS Forum

******************************************************************************
******************************************************************************

BIRD ID#:       95.4
ISSUE TITLE:    Power Integrity Analysis using IBIS
REQUESTER:      Syed Huq, Vinu Arumugham and Zhiping Yang, Cisco Systems, Inc.;
                Bob Ross, Teraspeed Consulting Group
DATE SUBMITTED: December 13, 2004  
DATE REVISED:   January 28, 2005, March 8, 2005, March 29, 2005, April 19, 2005
DATE ACCEPTED BY IBIS OPEN FORUM: PENDING 

******************************************************************************
******************************************************************************

STATEMENT OF THE ISSUE:

Power Integrity Analysis which includes Current switching profile of the Core
as well as Simultaneous Switching Noise (SSN) of states of a buffer is
to be analyzed through IBIS.

******************************************************************************

STATEMENT OF THE RESOLVED SPECIFICATIONS:

Power Integrity Analysis from a modeling perspective has been split into 
multiple tasks. Current into the power and ground rails are needed to give a 
more accurate analysis for ground and power bounce associated with simultaneous 
switching noise.

Solving the Simultaneous Switching Noise (SSN) will be achieved through 
the use of I-T tables in this proposal and the existing Series keywords.

****

Three sections in BIRD95.3 for [R_equiv], [L_Equiv], [C_Equiv], and [G_Equiv]
are REMOVED (but copied in the end for reference.  They dealt with the
keyword definition, tree diagram additions, and definition of the base units
mhos.

The [Composite Current] keyword is modified with references to [R_Equiv], etc.
removed and replaced with references to the Series keywords.

Also [Composite Current] is modified with references to the [Power Clamp
Reference] and [GND Clamp Reference] rails with respect to more description
on what [Composite Current] includes.  Some changes are noted with |**** lines.


|==============================================================================
|    Keywords:  [Composite Current]  
|    Required:  No
| Description:  Describes the shape of the rising and falling edge
|               current waveforms from the power supply measured through
|               the power pin terminal.
| Usage Rules:  The [Composite Current] keyword is positioned under the 
|               [Rising Waveform] (for rising waveform currents) and
|               [Falling Waveform] (for falling waveform currents.  The keywords 
|               are followed by a table of current versus time rows (I-T) that
|               describe the shape of a current waveform.  These I-T tables
|               inherit the fixture test load of the [Rising Waveform]
|               or [Falling Waveform] R/L/C/V_fixture and R/L/C_dut 
|               subparameters.
|
|               The [Composite Current] keyword is optional.  It can be omitted,
|               or it can be positioned under a few, but not all of the rising
|               and falling waveform tables.
|
|               The table itself consists of one column of time points, then
|               three columns of current points in the standard typ, min, and 
|               max format.  The four entries must be placed on a single line
|               and must be separated by at least one white space.  All four 
|               columns are required.  However, data is only required in the 
|	        typical column.  If minimum or maximum data is not available, 
|               use the reserved word "NA".  The first value in the time column 
|               need not be '0'.  Time values must increase as one parses down 
|		the table.  The waveform table can contain a maximum of 1000 
|               data points.
|
|               The I-T table data must be time-correlated with the V-T data
|               above.  That is, the currents documented in the I-T table
|               correspond to the voltages in the V-T table at the identical
|               time points and for the given *_fixture load.
|                
|               The following diagram illustrates a general configuration from
|               which a [Rising Waveform] or [Falling Waveform] is extracted.
|               The DUT die shows all of the available power and ground pin 
|               reference voltages.  For many buffers only one power pin and one 
|               common ground pin is used.  The absolute GND is the reference to 
|               the the V_fixture voltage and and the package model equivalent.  
|               It can also serve as a reference to C_comp, unless C_comp is 
|               optionally split into components attached to the other reference 
|               voltages.
|
|               The [Composite Current] I-T table includes all of the current
|               through the [Pullup Reference] terminal.  If the [POWER Clamp
|               Reference] is the same as the [Pullup Reference] (according
|               to the [Pin Mapping] keyword table), the [POWER Clamp] current
|               is included (for example, when on on-die terminator is
|               connected to the power pin).  
|
|
|           [External Reference] - if used
|
|           |  [POWER Clamp Reference] - if different
|           |
|           |  |  [Pullup Reference] - usually the Power Pin
|           |  |    ____  
|           |  |  | |    [Composite Current]
|           |  |  | V
|           |  |  |       PACKAGE            |   TEST FIXTURE
|          _|__|__|_                         |
|         |  DUT    |   L_dut   R_dut        | L_fixture  R_fixture
|         |  die    |---@@@@@--/\/\/\--o-----|--@@@@---o---/\/\/\--- V_fixture
|         |_________|                  |     |         |
|              |  |                    |     |         |
|              |  |                    |     |         |
|              |  |             C_dut ===    |        === C_fixture
|              |  |                    |     |         |
|              |  |                    |_____|_________|____________
|              |  |                          |                       GND
|              |
|              |  [Pulldown Reference] - usually the GND pin
|
|              [GND Clamp Reference] - if different
|
|
|               For *_ECL model types both the [Pullup Reference] and [Pulldown
|               Reference] terminals are connected.  The [Composite Current]
|               keyword therefore documents the currents through both terminals
|               and through both the [Pullup] and [Pulldown] tables.  The lowest
|               rail needs to be specified as either the default GND connection
|               or as an optional [GND Clamp Reference].
|
| Other Notes:  The diagram below documents some expected internal paths for a
|               useful special case where only one common power pin (VDDQ) and
|               one common ground exists (GND).
|                                  
| 
|   Black Box                                           [Composite Current] | VDDQ
|                                                                           | o
| __________________________________________________________________________| |__
||                                                                          | |  |
||                                                                          | |  |
||                                                                          v |  |
||                                                         -------- --------  |  |
||                                                         |      | |      |  |  |
||             ____________________________________________|L_VDDQ|_|R_VDDQ|__|  |
||            |                 |                |       | |      | |      |     |    
||            |                 |                |       | -------- --------     |
||         -----                |                |       |                       |
||	   | E |                |           |    |   |   |                       |
||         | S |        ----------------    |  P_|   |  --- POWER Clamp          |
||         | R |        |  Pre-Driver  |    | ||     |  / \                      |
||         -----        |   Circuit    |    | ||_    v  ---                      |
||           |          |  powered by  |    |    |       |                       |
||           |          |     VDDQ     |    |    | I_term|    I_sig              |
||         -----        ----------------    |    |       |   ------->            |
||         | E |                |           |    o-------o---------------------------o
||         | S |                |           |    |       |                       | Sig
||      |  | L |             |  |           |    |       |                       |
||      |  -----             |  |           |  N_|      --- GND Clamp            |
||      |    |               |  |           | ||        / \                      |
||      v    |               v  |           v ||_       ---                      |
||	   -----                |                |       |   ------  -------     |
||   I_byp ----- C_p+b    I_pre |         I_cb   |       |   |     | |     |     |
||	     |__________________|________________|_______|___|L_GND|_|R_GND|__   |
||                                                           |     | |     |  |  |
||                                                           ------  -------  |  |
||                                                                            |  |
||                                                                            |  |
||____________________________________________________________________________|__|
|                                                                             |
|                                                                             o  
|                                                                            GND
|
|       
|              Other elements in a more detailed typical (per buffer) model are:                          
|
|                 I_byp    - Bypass current
|                 I_pre    - Pre-Driver current
|                 I_cb     - Crow-bar current
|                 I_term   - Termination current (optional)
|                 L_VDDQ   - On-die inductance of I/O Power
|                 R_VDDQ   - On-die resistance of I/O Power
|                 L_GND    - On-die inductance of Ground
|                 R_GND    - On-die resistance of Ground
|                 C_p+b    - Bypass + Parasitic Capacitance
|                 ESR      - Equivalent Series Resistance for on-die Decap
|                 ESL      - Equivalent Series Inductance for on-die Decap
|
|

|**** References to [*_Equiv] removed from the next two paragraphs and the
|**** Text is changed to emphasize the Series keywords.


|              While the [Composite Current] already includes the buffer I_byp
|              current, some Series model type elements are used to document an
|              equivalent bypass impedance to improve simulation results.  
|              Such an equivalent impedance can be extracted on a per buffer
|              basis, but summed and expressed as a total equivalent impedance
|              between the power and ground pins with the Series model type
|              keywords including [C Series], [Lc Series], [Rc Series] and
|              [R Series] under a separate [Model] and with connections using
|              the [Series Pin Mapping] keyword.  Paths between several
|              voltage rails can be modeled in this manner.  The [Pin Mapping]
|              keyword documents what buffers share common and often isolated
|              power rails.
|
|              The C_p+b value might include the detailed distribution of C_comp
|              when C_comp* is attached to several rails.  If the C_comp value
|              and the C_p+b value are about the same magnitude, the [C Series]
|              value should be adjusted to avoid double counting.
|
|              The Power Pin terminal in most cases is the [Pullup Reference],
|              or the default [Voltage Range] terminal.  The [Pulldown Reference]
|              is usually the GND connection.
|
|              The [Composite Current] can still be defined for model types without
|              the [Pullup] keywords (such as Open_drain) because the [Pullup
|              Reference] or [Voltage Range] are still required.  Pre-driver and
|              other internal paths still can exist.
|              
|              In most cases six [Composite Current] tables are recommended
|              for accurate modeling.  The first four tables correspond to the 
|              recommended fixture conditions for [Rising Waveform] and [Falling
|              Waveform] tables (normally 50 ohm loads to Vdd and GND).  Two
|              additional waveforms for no load conditions (such as with an R_fixure
|              of 1.0 Megaohm) are useful.  However, some EDA tools process only
|              the first four waveforms.  So the additional open load waveforms for
|              I-T tables should be in [Rising Waveform] and [Falling Waveform]
|              tables that are positioned after the other V-T tables to maintain the
|              best output response simulation accuracy.
|
|              For Open-drain* and Open-source* technologies, two tables are
|              often specified (one for the [Rising Waveform] and one for the
|              [Falling Waveform]).  The tables should be positioned in front 
|              of any other optional waveform tables because some EDA tools
|              process just the first two tables.  Also, the open load tables
|              may not yield meaningful simulations unless internal on-die
|              terminators exist.
|
|              When the [Model] is configured for differential operation with the
|              [Diff Pin] keyword, the individual I-T currents for each [Model]
|              is used as an approximation, and may not accurately conform to
|              the measured currents under actual differential operation.
|             
|              The [Composite Current] table can be derived from currents measured
|              at the [Pulldown Reference] (GND) node, but adjusted for the
|              current flowing through the output pin and at other terminals.
|
|              The [Pin Mapping] keyword is used to document how buffers with
|              common voltage rails are connected.  The effective impedances for
|              each buffer between the [Pullup Reference] and [Pulldown Reference]
|              are then combined to form the total effective impedance between
|              the voltage rails.
|
|              The [Composite Current] keyword does not accurately document
|              the effects of controlled switching buffers such as those with
|              [Submodel] or [Driver Schedule] keywords.  The currents associated
|              with [Submodel] switching under specified test load conditions
|              can occur at different times under other load conditions.  The
|              scheduled models under the [Driver Schedule] keyword can be
|              attached to different voltage rails in an undocumented manner.
|------------------------------------------------------------------------------
|			
[Rising Waveform] 			
R_fixture = 50.0
V_fixture = 0.0
| ...
| ...            | Rising Waveform table
| ...						
[Composite Current]
|					
| Time            I(typ)      I(min)  I(max)
0		4.243E-05	NA	NA
4.00E-11	4.244E-05	NA	NA
8.00E-11	4.242E-05	NA	NA
1.20E-10	4.265E-05	NA	NA
1.60E-10	3.610E-05	NA	NA
2.00E-10	3.903E-03	NA	NA
..
..
..
3.80E-09	2.012E-02	NA	NA
3.84E-09	2.012E-02	NA	NA
3.88E-09	2.012E-02	NA	NA
3.92E-09	2.012E-02	NA	NA
3.96E-09	2.012E-02	NA	NA
4.00E-09	2.012E-02	NA	NA
|			
[Falling Waveform] 			
R_fixture = 50.0
V_fixture = 1.8
| ...
| ...            | Falling Waveform table
| ...
[Composite Current]
|				
| Time            I(typ)      I(min)  I(max)	
0		4.302E-05	NA	NA
4.00E-11	4.299E-05	NA	NA
8.00E-11	4.304E-05	NA	NA
1.20E-10	4.287E-05	NA	NA
1.60E-10	4.782E-05	NA	NA
2.00E-10	1.459E-04	NA	NA
..
..
..
3.80E-09	4.933E-05	NA	NA
3.84E-09	5.211E-05	NA	NA
3.88E-09	5.490E-05	NA	NA
3.92E-09	5.441E-05	NA	NA
3.96E-09	4.842E-05	NA	NA
4.00E-09	4.244E-05	NA	NA
|
| ... etc.
|
|==============================================================================


***

The following entries are made to the Tree diagram in Section 3a under the
[Model] keywords as noted by the |*** lines:  (The [*_Equv] keyword entries
are removed in BIRD95.4.)


|  |     |-- [Ramp]                         dV/dt_r, dV/dt_f,
|  |     |-- [Rising Waveform]              R_fixture, V_fixture,
|  |     |                                  V_fixture_min, V_fixture_max,
|  |     |                                  C_fixture, L_fixture, R_dut, L_dut,
|  |     |                                  C_dut

|*** Add this keyword

|  |     |   -----------------
|  |     |      |
|  |     |      |-- [Composite Current]
|  |     |

|*** End of addition

|  |     |-- [Falling Waveform]             R_fixture, V_fixture,
|  |     |                                  V_fixture_min, V_fixture_max,
|  |     |                                  C_fixture, L_fixture, R_dut, L_dut,
|  |     |                                  C_dut

|*** Add this keyword

|  |     |   -----------------
|  |     |      |
|  |     |      |-- [Composite Current]
|  |     |

|*** End of addition

|  |     |-- [Test Data]                    Test_data_type *, Driver_model, 
|  |     |                                  Driver_model_inv, Test_load
|  |     |   -----------


******************************************************************************

ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:

Power Integrity Analysis has become a significat part of Signal Integrity 
Simulations and Analysis. Core voltages are going down with process
enhancement and, I/O speeds are increasing, it is critical that 
high-speed applications solve Power Integrity issues on the die, package 
and PCBs combined. System failures can be traced to poor Power Integrity 
Designs.

During the DesignCon2004 Power Integrity Panel, these issues were discussed.
It was suggested to explore a solution through the IBIS commitee and hence
this BIRD proposal.

Several discussions were conducted(3/12/04,5/14/04,6/8/04,7/16/04,8/24/04)
with the IBIS Futures Meetings. 

BIRD95.3:

Based on comments and intent of BIRD95.2, the following changes were made:

Subparameters for R_zvddq, L_zvddq, C_zvddq, and G_zvddq were changed to
four keywords under [Model]: [R Equiv], [L Equiv], [C Equiv] and [G Equiv].
for the following reasons: (1) avoid repeating the same values for each
occurance of [Composite Current] because there was never the intention
to support different values, (2) to allow for typ-min-max values under the
extraction conditions.

The name change in keywords was made to conform better to the illustrative
diagram components (ESR, ESL, etc) and to emphasize that these are overall
equivalent values.

A consequence of this syntactical change is that these keywords can be
used whether or not [Composite Current] is defined.  This is good because
gate modulation control sometimes is sufficient in some devices.

Several syntactical choices exist: (1) uses the [Series Pin Mapping] keyword
and the already defined Series models, (2) write as subparameters under model
similar to C_comp, (3) capture the group under new keyword (such as [Zvddq])
under [Model], but use a subparameter format under this like [Package] and
R_pin, etc. (4) define as independent keywords such as [R Equiv], etc. like
the [Rgnd], [Rpower] terimnator elements, (5) do nothing and rely on some
future connection to hook up ICM with IBIS.

Choice (1) has syntactical might not be available on a per buffer basis.
Also, this requires a complete [Series Pin Mapping] pinout of all such
connections along with the [Pin Mapping] keyword.  Using the (2) subparameter
method directly under [Model] is a syntactical departure from what we have
traditionally done.  Even some [Model Spec] subparameters are grouped under
a keyword for grouping purpose. (Putting these additional impedances under
[Model Spec] was also rejected because the describe electrical content, not
specification information or specification test setups.)  Positioning the
subparameters under a keyword (such as [Zvvdq]) for grouping purposes is the
preferred alternative and was almost used for BIRD95.3.  While it has grouping
advantages for content location purposes, and while it may follow the syntax
similar to [Package] and its R_pin, L_pin, and C_pin subparameters, all
electrical content under the [Model] keyword are described by keywords such
as those for I-V tables, and terminators (e.g., [Rac], [Cac], [Rpower], [Rgnd])
or [TTpower], [TTgnd].  The choice for using the keyword format follows from
these cases.  The C_comp* subparameters remain the only exception.

The other detail concerns more resolution on ECL/PECL support.  The problem
is that the negative reference supply is not required.  The options are
to simply list this as an unsupported exception at this time, or to add
more requirements and conditions.  The choice is changed to specify that
it is not supported and leave its support to other BIRDs if there is a
compelling industrial need.

Some other changes per the discussion at the March 11, 2005 meeting:

1) _typ, _min, _max for the sub-params - Itzik Peleg
 Added with the four new keywords.

2) C_comp for Power and GND and it's relation to this BIRD - Arpad Muranyi
 Added by stating that C_comp* is assumed separate from [C Equiv].

3) C_p+b, Is this Total or per I/O - John Angulo
 Stated per I/O

4) On-die cap for power rail, is this included or not - Michael Mirmak
 Assumed separate, if it exists and modeled by [C Series]

5) Make a statement that says, this is for a single buffer and not a complete
   component - John Angulo
 Assumed per single buffer by statements and positioning under [Model]

6) Z_VDDDQ subparams and placement under Model_type - Bob Ross/John Angulo
 Added statement that the new keywords might not be used for Input, Terminator,
 Series, Series Switch, Input_diff model_type.  The positioning of [Composite
 Current] under the [Rising Waveform] and [Falling Waveform] keywords already
 constrain that it is used only where the waveform tables are used.


The tree diagram and addition of mho as a base unit is added for completeness.
Some Editorial changes and corrections are made.


BIRD95.4

Several questions arose regarding the details of the [*_Equiv] keyword and
how they would be impacted when other voltage rails such as [POWER Clamp
Reference] were defined.  Also several people were concerned that the
additions did no allow for additional internal paths to the other rails.

Since the effect can be captures with the existing Series keywords [R Series],
[C Series], [Rc Series] and [Lc Series] keywords, in a more general manner
to each supply, BIRD95.4 makes reference to these.

Also, more details are given for the other power rails.

The *_ECL discussion is modified to indicate that the [Composite Current]
flow through both the [Pullup Reference] and [Pulldown Reference] connections.
If this mode is supported, then the EDA tool algorithms must deal with *_ECL
technologies differently than non-ECL technologies.  In all cases, BIRD95.4
docuemnts what is in the model, not how the information is processed.

The black box reference diagram has been modified to remove the extra internal
termination resistors.  Normally they are modeled with the clamp tables.  The
I_term current is moved to the clamp tables.  All the currents are modified
so they flow through the top-most internal element.

******************************************************************************

ANY OTHER BACKGROUND INFORMATION:

Other Power Integrity Related BIRDs are planned, but there may be future
issues regarding exactly what is adopted to be discussed separately.  Other
than the already proposed BIRD97, BIRD95.3 has sufficient content for a
complete solution at a lower level without these planned BIRDs:

Linkage to a Core model will be achieved by BIRDXX (TBD).
Linkage to an ICM model will be achieved by BIRDYY (TBD).
Linkage to a Gate Modulation model will be achieved by BIRD97.

This proposal is based on various past work done by many IBIS contributors and 
they are listed in no particular order. Links to ICEM are also listed:	

DesignCon2004 PDN Simulation panel proceedings material and slides:
http://home.att.net/~istvan.novak/papers.html


BIRD42.3: Modeling Current Waveforms
          C. Kumar, Bob Ross
IBIS and ICEM interaction: B. Ross, Microelectronic Journal November 16, 2003

ICEM:	 
----
EMC for Component, Integrated circuits Electrical Model(ICEM)
                93/XX/CDC, Project number 62014-3
Cookbook for Integrated Circuit model ICEM, Project number 62014-3

IBIS Summits: 
-------------
EMC model for prediction of parasitic emission, E. Sicard, March 2001
Electromagnetic Compatibility simulation of Printed Circuit Board, M. Christian,
  March 2001
ICEM - Proposal IEC62014-3, J.C.Perrin, March 2001
Advances of the ICEM model for Emission of Integrated Circuit, S. Calvet,
  January 2001
Adding On-Chip Capacitance in IBIS Format for SSO Simulation, R. Chen,
  January 2004
Simultaneous Switching Noise(SSN)Modeling, B. Unger January 2000
Crossbar-current out of CMOS-IBIS-Models, K. Koller & G .Bannert, March 2002
IC-Emit Comparing Simulated/Measured IC Emission Spectrum,
  E. Sicard & A. Soubeyran Februayr 2004

REVISION HISTORY CHANGES:

Replace following BIRD95.1 lines:
|*Power Integrity Analysis from a modeling perspective has been split into 
|*two tasks. 

|*1)Solving the Simultaneous Switching Noise (SSN) on the I/O level using current 
|*  and future IBIS syntax. This will be achieved through IvsT tables.
  
|*2)Solving the Core Current Switching profile using the ICEM (Integrated circuits 
|*  Electrical Model specification, Project number 62014-3). This will be achieved 
|*  by a call statement within IBIS calling an ICEM model. Using v4.1 IBIS syntax.


replace:
Current into the power and ground rails are needed to give a more accurate
analysis for ground and power bounce associated with simultaneous switching noise.

replace:
|     Keywords:     [Series Composite Current] 

with:
replace:
|     Description:  Describes the shape of the rising and falling edge
|                   current waveforms from the power supply measured through
|                   R_VDD(see diagram). This includes Pre-driver, Crow-bar current,
|                   on-die I_bypass and I_term(see diagram).


replace:
|     Usage Rules:  The [Series Composite Current] keyword is positioned under the

replace:
|                                  
|    
|                                                           -------- -------- (**)
|                                                           |      | |      |<---
|              _____________________________________________|L_VDDQ|_|R_VDDQ|__VDDQ
|             |                   |         |     |       | |      | |      |          
|             |                   |         |     |       | -------- --------
|           -----                 |         |     |       |   
|	    | E |                 |         /     |       |
|           | S |        ----------------   \   P_|      --- PowerClamp
|           | R |        |  Pre-Driver  |   / ||         / \
|           -----        |   Circuit    |   \ ||__       ---
|             |          |  powered by  |   |     |       |
|             |          |     VDDQ     |   |     |  |    |   I_sig
|           -----        ----------------   |     |  |    |   ------->
|           | E |                 |         o-----o--|----o----------
|           | S |                 |         |     |  |    |
|	 |  | L |            |    |      |  /     |  |    |
|I_bypass|  -----       I_pre|    |I_term|  \   N_|  v   --- GNDClamp
|	 |    |              |    |      |  /  ||   I_cb / \
|	 v    |              v    |      v  \  ||_       ---
|	    -----                 |         |     |       |   ------  -------
|	    ----- C_p+b           |         |     |       |   |     | |     |
|	      |___________________|_________|_____|_______|___|L_GND|_|R_GND|__GND
|                                                             |     | |     |
|                                                             ------  -------
|
|            I_bypass - Bypass current
|            I_pre    - Pre-Driver current
|            I_cb     - Crow-bar current
|            I_term   - Termination current (optional)
|            L_VDDQ   - On-die inductance of I/O Power
|            R_VDDQ   - On-die resistance of I/O Power
|            L_GND    - On-die inductance of Ground
|            R_GND    - On-die resistance of Ground
|            C_p+b    - Bypass + Parasitic Capacitance
|            ESR      - Equivalent Series Resistance for on-die Decap
|            ESL      - Equivalent Series Inductance for on-die Decap
|
|            (**)     - Current measure point


The original BIRD95.2 [Composite Current] writeup is captured here for
historical reference.

|==============================================================================
|    Keywords:  [Composite Current]  
|    Required:  No
| Description:  Describes the shape of the rising and falling edge
|               current waveforms from the power supply measured through
|               the power pin terminal illustrated more fully in the Usage
|               Rules.
|  Sub-params:  R_zvddq, R L_zvddq, C_zvddq_typ, G_zvddq
| Usage Rules:  The [Composite Current] keyword is positioned under the 
|               [Rising Waveform] (for rising waveform currents) and
|               [Falling Waveform] (for falling waveform currents.  The keywords 
|               are followed by optional on-die parasitic die subparameters and
|               then a table of current versus time rows (I-T) that
|               describe the shape of a current waveform.  These I-T tables
|               inherit the fixture test load of the [Rising Waveform]
|               or [Falling Waveform] R/L/C/V_fixture and R/L/C_dut 
|               subparameters.
|
|               The [Composite Current] keyword is optional.  It can be omitted,
|               or it can be positioned under a few, but not all of the rising
|               and falling waveform tables.
|
|               The listed subparemeters, R_zvddq, L_zvddq, C_zvddq, and G_zvddq,
|               describe the impedance path between the power pin terminal and
|               ground (see Other Notes below).  The first three subparameters
|               describe a series path of resistance, inductance and capacitance.
|               The forth subparameter describe a separate path in parallel to
|               the series path and also between the power pin terminal and
|               ground.
|
|               These subparameters are optional, but if any are missing, they
|               take on a default value of zero.  Thus C_zvddq, if missing, opens
|               the series path, and if R_zvddq is missing, the resistance is
|               assumed zero.  If G_zvddq is missing, it is not included in the
|               model
|
|               The I-T table follows these subparameters.  The table itself               
|               consists of one column of time points, then 
|               three columns of current points in the standard typ, min, and 
|               max format.  The four entries must be placed on a single line and
|               must be separated by at least one white space.  All four 
|               columns are required.  However, data is only required in the 
|	        typical column.  If minimum or maximum data is not available, 
|               use the reserved word "NA".  The first value in the time column 
|               need not be '0'.  Time values must increase as one parses down 
|		the table.  The waveform table can contain a maximum of 1000 
|               data points.
|                
|               The following diagramss illustrate a typical configurating which
|               a [Rising Waveform] or [Falling Waveform is extracted.  The
|               DUT die is modified to include the Power Pin and Ground Pin.
|
|        
|   Power Pin  |
|              |
|              |
|              |          PACKAGE            |   TEST FIXTURE
|          ____|____                         |
|         |  DUT    |   L_dut   R_dut        | L_fixture  R_fixture
|         |  die    |---@@@@@--/\/\/\--o-----|--@@@@---o---/\/\/\--- V_fixture
|         |_________|                  |     |         |
|              |                       |     |         |
|              |                       |     |         |
|              |                C_dut ===    |        === C_fixture
|              |                       |     |         |
|              |_______________________|_____|_________|___
|  Ground Pin                                |             GND
|
|
|               The [Composite Current] direction is shown with respect to the
|               Power Pin and the new subparameters are added to the DUT die.
|               These subparameters do not effect the [Rising Waveform and
|               [Falling Waveform] table extractions, but give added equivalant
|               circuit detail for more accurate power pin current calculations.
|
|
!                                            [Composite Current]
|                                                   <------
|                               __________________________________ Rower Pin
|                              |
|           ___________________|_______________________ 
|          |                   |                       |
|          |        ___________|______________         |
|          |   ____|____       |              |        |
|          |  |         |      |              |  DUT   |
|          |  | R_zvddq |      |              |  die   |
|          |  |_________|      |              |        |
|          |   ____|____   ____|____      ____|____    |
|          |  |         | |         |    |  I/O    |   |
|          |  | L_zvddq | | G_zvddq |    |  die    |-------------- To L_dut
|          |  |_________| |_________|    |_________|   |
|          |   ____|____       |              |        |
|          |  |         |      |              |        |
|          |  | C_zvddq |      |              |        |
|          |  |_________|      |              |        |
|          |       |___________|______________|        |
|          |                   |                       |
|          |___________________|_______________________|
|                              |
|                              |________________________________  Ground Pin
|                               
|
|
| Other Notes:  The internal networks for the DUT die 'Black Box' are shown
|               below to illustrate the effects that the equivalent circuit
|               are intended to describe.  The Power Pin terminal is ahown as
|               VDDQ, and the Ground Pin terminal is shown as GND.
|                                  
| 
| 
|                                                                           VDDQ
|   Black Box                                                           (**)  o
| ___________________________________________________________________________||__
||                                                                           ||  |
||                                                                           ||  |
||                                                                           v|  |
||                                                         -------- --------  |  |
||                                                         |      | |      |  |  |
||             ____________________________________________|L_VDDQ|_|R_VDDQ|__|  |
||            |                  |         |     |       | |      | |      |     |    
||            |                  |         |     |       | -------- --------     |
||         -----                 |         |     |       |                       |
||	   | E |                 |         /     |       |                       |
||         | S |        ----------------   \   P_|      --- PowerClamp           |
||         | R |        |  Pre-Driver  |   /  ||        / \                      |
||         -----        |   Circuit    |   \  ||_       ---                      |
||           |          |  powered by  |   |     |       |                       |
||           |          |     VDDQ     |   |     |  |    |   I_sig               |
||         -----        ----------------   |     |  |    |   ------->            |
||         | E |                 |         o-----o--|----o---------------------------o
||         | S |                 |         |     |  |    |                       | Sig
||	 | | L |            |    |      |  /     |  |    |                       |
|| I_byp|  -----       I_pre|    |I_term|  \   N_|  v   --- GNDClamp             |
||	 |   |              |    |      |  /  ||   I_cb / \                      |
||	 v   |              v    |      v  \  ||_       ---                      |
||	   -----                 |         |     |       |   ------  -------     |
||	   ----- C_p+b           |         |     |       |   |     | |           |
||	     |___________________|_________|_____|_______|___|L_GND|_|R_GND|__   |
||                                                           |     | |     |  |  |
||                                                           ------  -------  |  |
||                                                                            |  |
||                                                                            |  |
||____________________________________________________________________________|__|
|                                                                             |
|                                                                             o  
|                                                                            GND
|
|                 (**)       I-T    - current through VDDQ terminal.
|       
|              Other elements typically in a more detailed model are                                
|
|                 I_byp    - Bypass current
|                 I_pre    - Pre-Driver current
|                 I_cb     - Crow-bar current
|                 I_term   - Termination current (optional)
|                 L_VDDQ   - On-die inductance of I/O Power
|                 R_VDDQ   - On-die resistance of I/O Power
|                 L_GND    - On-die inductance of Ground
|                 R_GND    - On-die resistance of Ground

|                 C_p+b    - Bypass + Parasitic Capacitance
|                 ESR      - Equivalent Series Resistance for on-die Decap
|                 ESL      - Equivalent Series Inductance for on-die Decap
|
|          
|              The subparameters R_zvddq, L_zvddq, C_zvddq and G_zvddq represent
|              and effective impedance of the internal Power pin to Ground pin
|              elements, as extracted from the terminals.  In the future, the ICM
|              format might proivde more accurate detail, if needed.

|              NOTE: The Power Pin terminal in most cases is the [Pullup Reference],
|              or the default [Voltage Range] value.  This [Pullup Reference] can
|              also be GND, as in some *_ECL technologies, and the Ground Pin is the
|              more negative reference.  In such cases, the [GND Clamp Reference]
|              value should be defined.
|
|              If [POWER Clamp Reference] or [GND Clamp Reference] are different
|              than the [Pullup Reference] or [Pulldown Reference] voltages,
|              the model may not account for all of the currents.  However, the
|              simulatiion should still closely approximate the current transients.
|
|              The [Composite Current] can still be defined for Model_types with
}              out the [Pullup] keywords (such as Open_drain) because the [Pullup
|              Reference] or [Voltage Range] are still required.  Pre-driver and
|              other internal paths still exist.
|              
|              NOTE: In most cases six [Composite Current] tables are recommended
|              for accurate modeling.  The first four tables correspond to the 
|              recommended fixture conditions for [Rising Waveform] and [Falling
|              Waveform] tables (normally 50 ohm loads to Vdd and GND).  Two
|              additional waveforms for no load conditions (such as with an R_fixure
|              of 1.0 megaohm are useful.  However, some EDA tools may use only
|              the first four waveforms.  So these additional open load waveform
|              I-T tables should be in [Rising Waveform] and [Falling Waveform]
|              tables positioned after the other V-T tables to maintain the best
|              output response accuracy.  These extra two tables do not apply
|              for any of the Open-drain and Open-source technologies or for
|              ECL technologies.
|
|              When the [Model] is configured differentially with the [Diff Pin]
|              keyword, the individual I-T currents for each [Model] is used as
|              an approximation.  This summation may not be as accurate as the
|              the actual measured currents under actual operation.
|             
|              The [Composite Current] table can be derived from currents measured
|              at the GND node that have been transformed by combining with the
|              current at the output pin.
|
|              The [Pin Mapping] keyword is used to docuemnt the voltage rails
|              of several buffers are combined.  This combination includes the
|              effective impedances describe for each buffer
|
|              The [Composite Current] keyword is not designed to accurately
|              document the effects of controlled switching buffers such as
|              those defined with [Submodel] or [Driver Schedule] keywords.
|------------------------------------------------------------------------------
|			
[Rising Waveform] 			
R_fixture = 50.0
V_fixture = 0.0
| ...
| ...            | Rising Waveform table
| ...						
[Composite Current]
R_zvddq = 2.0m
L_zvddq = 0.2n
C_zvddq = 2.0p
G_zvddq = 2.0u
|					
| Time            I(typ)      I(min)  I(max)
0		4.243E-05	NA	NA
4.00E-11	4.244E-05	NA	NA
8.00E-11	4.242E-05	NA	NA
1.20E-10	4.265E-05	NA	NA
1.60E-10	3.610E-05	NA	NA
2.00E-10	3.903E-03	NA	NA
..
..
..
3.80E-09	2.012E-02	NA	NA
3.84E-09	2.012E-02	NA	NA
3.88E-09	2.012E-02	NA	NA
3.92E-09	2.012E-02	NA	NA
3.96E-09	2.012E-02	NA	NA
4.00E-09	2.012E-02	NA	NA
|			
[Falling Waveform] 			
R_fixture = 50.0
V_fixture = 1.8
| ...
| ...            | Falling Waveform table
| ...						
[Composite Current]	
R_zvddq = 2.0m
L_zvddq= 0.2n
C_zvddq = 2.0p
G_zvddq = 2.0u
|				
| Time            I(typ)      I(min)  I(max)	
0		4.302E-05	NA	NA
4.00E-11	4.299E-05	NA	NA
8.00E-11	4.304E-05	NA	NA
1.20E-10	4.287E-05	NA	NA
1.60E-10	4.782E-05	NA	NA
2.00E-10	1.459E-04	NA	NA
..
..
..
3.80E-09	4.933E-05	NA	NA
3.84E-09	5.211E-05	NA	NA
3.88E-09	5.490E-05	NA	NA
3.92E-09	5.441E-05	NA	NA
3.96E-09	4.842E-05	NA	NA
4.00E-09	4.244E-05	NA	NA
|
| ... etc.
|
|------------------------------------------------------------------------------


BIRD95.4:

The following section in BIRD95.3 was removed:



The [R Equiv], [L Equiv], [C Equiv] and [G Equiv] keywords are entered above
the [Ramp] keyword in the document:


|==============================================================================
|    Keywords:  [R Equiv], [L Equiv], [C Equiv], [G Equiv]  
|    Required:  No
| Description:  Describes the impedance between the [Pullup Reference] and
|               [Pulldown Reference] in terms of a resistance, inductance,
|               capacitance in series and a parallel conductance.
| Usage Rules:  These keywords are positioned with the other keywords under the
|               [Model] keyword.
|              
|               For each of these keywords, the three columns hold the
|               typical, minimum, and maximum values.  The three
|               entries must be placed on a single line and must be separated
|               by at least one white space.  All three columns are required
|               under these subparameters.  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 that
|               the typical column entry will be used.
|
|               These keywords are optional, but if any are missing, it takes
|               on a default value of zero.  Thus [C Equiv], if missing, opens
|               the series path, and if [R Equiv] is missing, the resistance is
|               assumed zero.  If [G Equiv] is missing, it is not included in
|               the model
|
|               The keyword connections are defined with respect to reference
|               diagram in parallel to an I/O pin on the die on a per buffer
|               basis.  The Power Pin is
|               the [Pullup Reference] and the Ground Pin is the [Pulldown
|               [Reference].
|
|
|
|                               __________________________________ Power Pin
|                              |                          [Pullup Reference]
|           ___________________|_______________________ 
|          |                   |                       |
|          |        ___________|______________         |
|          |   ____|____       |              |        |
|          |  |         |      |              |        |
|          |  |[R Equiv]|      |              |  Die   |
|          |  |_________|      |              |        |
|          |   ____|____   ____|____      ____|____    |
|          |  |         | |         |    |  I/O    |   |
|          |  |[L Equiv]| |[G Equiv]|    |  die    |-------------- 
|          |  |_________| |_________|    |_________|   |
|          |   ____|____       |              |        |
|          |  |         |      |              |        |
|          |  |[C Equiv]|      |              |        |
|          |  |_________|      |              |        |
|          |       |___________|______________|        |
|          |                   |                       |
|          |___________________|_______________________|
|                              |
|                              |________________________________  Ground Pin
|                                                       [Pulldown Reference]
|
|
|               These Keywords might not be effective for *_ECL technologies
|               because the [Pullup Reference] and [Pulldown Reference] are
|               connected to the same rail (which also can be Ground), and the
|               the most negative rail might not be specified.
|
|               These keywords might not have any effect for the Model_type
|               settings of Input, Input_diff, Terminator, Series, and
|               Series_switch.  These settings do not have a driver mode of
|               operation.
|
| Other Notes:  The [R Equiv], [L Equiv], [C Equiv] and [G Equiv] keywords may
|               be used with, but do not require the [Composite Current] keyword
|               described later.  Also, an example of a more detailed internal
|               network for these equivalent impedances is presented under the
|               [Composite Current] keyword.
|------------------------------------------------------------------------------
| variable     Typ           Min          Max
|
[R Equiv]      2.0m          NA           NA
[L Equiv]      0.2n          .3n          .1n     | Follow Process, Temperature
[C Equiv]      2.0p          1.0p         1.3p    | Voltage conditions with no
[G Equiv]      2.0u          NA           NA      | Ordering of values assumed
|
|==============================================================================

***

The following entries are made to the Tree diagram in Section 3a under the
[Model] keywords as noted by the |*** lines:


|  |     |-- [Lc Series]             
|  |     |-- [Rc Series]             
|  |     |-- [Series Current]        
|  |     |-- [Series MOSFET]                Vds

|*** Add these keywords

|  |     |-- [R Equiv]
|  |     |-- [L Equiv]
|  |     |-- [C Equiv]
|  |     |-- [G Equiv]

|*** End of addition


***

The following change is made in Section 2, item 8) to add mho as a base unit
as denoted in the |*** line:


| 8)  Valid scaling factors are:
|         T = tera        k = kilo        n = nano
|         G = giga        m = milli       p = pico
|         M = mega        u = micro       f = femto
|     When no scaling factors are specified, the appropriate base units are
|***  assumed.  (These are volts, amperes, ohms, mhos, farads, henries, and
|     seconds.)  The parser looks at only one alphabetic character after a
|     numerical entry, therefore it is enough to use only the prefixes to
|     scale the parameters.  However, for clarity, it is allowed to use full
|     abbreviations for the units, (e.g., pF, nH, mA, mOhm).  In addition,
|     scientific notation IS allowed (e.g., 1.2345e-12).

******************************************************************************


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Received on Tue Apr 19 18:36:18 2005

This archive was generated by hypermail 2.1.8 : Tue Apr 19 2005 - 18:41:02 PDT