******************************************************************************
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BIRD ID#:        103.1
ISSUE TITLE:     [Model Spec] DDR2 Overshoot/Undershoot Parameters
REQUESTER:       Randy Wolff, Micron Technology, Inc.
DATE SUBMITTED:  April 14, 2006; May 10, 2006
DATE ACCEPTED BY IBIS OPEN FORUM: June 2, 2006

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

STATEMENT OF THE ISSUE:

The JEDEC DDR2 SDRAM Specification (JESD79-2A) specifies AC overshoot and 
undershoot in terms of a maximum area above or below specific voltage
thresholds.  A maximum overshoot/undershoot amplitude is also defined.  The
parameters available for [Model Spec] do not provide a way to check for
violations of this overshoot/undershoot condition as calculated by area.  
The dynamic overshoot/undershoot parameters can specify time and maximum
voltage, but these are not adequate to define an area in terms of  V-s. 

This BIRD proposes adding four new parameters to the IBIS specification
under [Model Spec] that will give EDA software the conditions necessary to
check for overshoot/undershoot violations on DDR2 SDRAM devices and issue
warnings.

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

STATEMENT OF THE RESOLVED SPECIFICATIONS:

All changes, with the exception of spacing and line break adjustments, are 
shown with |*.  Changes in revision 103.1 are shown with |**.

|*****************************************************************************
|* ORIGINAL [Model Spec] TEXT
|*****************************************************************************
|=============================================================================
|     Keyword:  [Model Spec]
|    Required:  No
|  Sub-Params:  Vinh, Vinl, Vinh+, Vinh-, Vinl+, Vinl-, S_overshoot_high,
|               S_overshoot_low, D_overshoot_high, D_overshoot_low,
|               D_overshoot_time, Pulse_high, Pulse_low, Pulse_time, Vmeas,
|               Vref, Cref, Rref, Cref_rising, Cref_falling, Rref_rising,
|               Rref_falling, Vref_rising, Vref_falling, Vmeas_rising, 
|               Vmeas_falling, Rref_diff, Cref_diff
| Description:  The [Model Spec] keyword defines four columns under which
|               specification subparameters are defined.  
|               
|               The following subparameters are defined:
|               Vinh               Input voltage threshold high
|               Vinl               Input voltage threshold low
|               Vinh+              Hysteresis threshold high max Vt+
|               Vinh-              Hysteresis threshold high min Vt+
|               Vinl+              Hysteresis threshold low max Vt-
|               Vinl-              Hysteresis threshold low min Vt-
|               S_overshoot_high   Static overshoot high voltage
|               S_overshoot_low    Static overshoot low voltage
|               D_overshoot_high   Dynamic overshoot high voltage
|               D_overshoot_low    Dynamic overshoot low voltage
|               D_overshoot_time   Dynamic overshoot time
|               Pulse_high         Pulse immunity high voltage
|               Pulse_low          Pulse immunity low voltage
|               Pulse_time         Pulse immunity time
|               Vmeas              Measurement voltage for timing measurements
|               Vref               Timing specification test load voltage
|               Cref               Timing specification capacitive load
|               Rref               Timing specification resistance load
|               Cref_rising        Timing specification capacitive load for
|                                  rising edges
|               Cref_falling       Timing specification capacitive load for
|                                  falling edges
|               Rref_rising        Timing specification resistance load for
|                                  rising edges
|               Rref_falling       Timing specification resistance load for
|                                  falling edges
|               Vref_rising        Timing specification test load voltage for
|                                  rising edges
|               Vref_falling       Timing specification test load voltage for
|                                  falling edges
|               Vmeas_rising       Measurement voltage for rising edge timing
|                                  measurements
|               Vmeas_falling      Measurement voltage for falling edge timing
|                                  measurements
|               Rref_diff          Timing specification differential
|                                  resistance load
|               Cref_diff          Timing specification differential
|                                  capacitive load
|
| Usage Rules:  [Model Spec] must follow all other subparameters under the 
|               [Model] keyword.
|
|               For each subparameter contained in the first column, the 
|               remaining three hold its typical, minimum and maximum values.
|               The entries of typical, minimum and maximum must be placed on
|               a single line and must be separated by at least one white
|               space.  All four columns are required under the [Model Spec]
|               keyword.  However, data is required only in the typical
|               column.  If minimum and/or maximum values are not available,
|               the reserved word "NA" must be used indicating the typical
|               value by default.
|
|               The minimum and maximum values are used for specifications
|               subparameter values that may track the min and max operation
|               conditions of the [Model].  Usually it is related to the
|               Voltage Range settings.
|
|               Unless noted below, no subparameter requires having present
|               any other subparameter.
|      
|               Vinh, Vinl rules:
| 
|               The threshold subparameter lines provide additional min and
|               max column values, if needed.  The typ column values are still
|               required and would be expected to override the Vinh and Vinl
|               subparameter values specified elsewhere.  Note: the syntax
|               rule that require inserting Vinh and Vinl under models remains
|               unchanged even if the values are defined under the [Model
|               Spec] keyword.
|
|               Vinh+, Vinh-, Vinl+, Vinl- rules:
|
|               The four hysteresis subparameters (used for Schmitt trigger
|               inputs for defining two thresholds for the rising edges and
|               two thresholds for falling edges) must all be defined before
|               independent input thresholds for rising and falling edges of
|               the hysteresis threshold rules become effective.  Otherwise
|               the standard threshold subparameters remain in effect.  The
|               hysteresis thresholds shall be at the Vinh+ and Vinh- values
|               for a low-to-high transition, and at the Vinl+ and Vinl-
|               values for a high-to-low transition.
|
|         |
|         |           Receiver Voltage with Hysteresis Thresholds
|         |
|         |
|         |       Rising Edge                            Falling Edge
|         |    Switching Region   oo    o              Switching Region
|         |                  |  o    oo  ooooooooo           |
|         |                  V o                    o        |
|  Vinh+  - - - - - - - - - - x                        o     |
|  Vinh-  - - - - - - - - -  x                           o   |
|         |                 o                             o  |
|         |                o                               o |
|         |               o                                 oV
|  Vinl+  - - - - - - -  o - - - - - - - - - - - - - - - - - x
|  Vinl-  - - - - - - - o  - - - - - - - - - - - - - - - - -  x
|         |           o                                         o
|         |        o                                               o
|         |oooooo-----------------------------------------------------oooooooo
|
|                                       Time -->
|
|               S_overshoot_high, S_overshoot_low rules:
|
|               The static overshoot subparameters provide the DC voltage
|               values for which the model is no longer guaranteed to function
|               correctly.  Typically these are voltages that would cause the
|               physical component to be destroyed.
|
|               D_overshoot_high, D_overshoot_low, D_overshoot_time rules:
|
|               The dynamic overshoot values provide a time window during
|               which the overshoot may exceed the static overshoot limits
|               but be below the dynamic overshoot limits.  D_overshoot_time
|               is required for dynamic overshoot testing.  In addition, if
|               D_overshoot_high is specified, then S_overshoot_high is
|               necessary for testing beyond the static limit.  Similarly, if
|               D_overshoot_low is specified, then S_overshoot_low is
|               necessary for testing beyond the static limit.
|                
|         |
|         |     Receiver Voltage with Static and Dynamic Overshoot Limits
|         |
|         |
|         |   D_overshoot_time ->|      |<-
|         |                      |      |
|  D_overshoot_high - - - - - - -+ - - -+                       
|         |                      | oo   |  Passes - Does Not Exceed Bounds
|         |                      |o  o  |
|  S_overshoot_high - - - - - - -x    o +- - - - - - - - - - - - - - - - - - -
|         |                     o      o ooooooooo 
|         |                    o        o         o
|         |                   o                    o
|         |                  o                      o
|         |                 o                        o
|         |                o                          o
|         |               o                            o
|         |              o                              o        Fails -
|         |             o                                o    Exceeds Bounds
|         |           o                                   o      |   |  |
|         |        o                                       o     V   V  V
|         |oooooo-------------------------------------------o---------o---oooo
|  S_overshoot_low - - - - - - - - - - - - - - - - - - - - - x      +x x x - -
|         |                                                  |o     x   x
|         |                                                  | o   o|
|  D_overshoot_low - - - - - - - - - - - - - - - - - - - - - + -x x-+
|         |                                                  |   x  |
|                                         D_overshoot_time ->|      |<-
|
|                                       Time -->
|
|               Pulse_high, Pulse_low, Pulse_time rules:
|
|               The pulse immunity values provide a time window during which
|               a rising pulse may exceed the nearest threshold value but
|               be below the pulse voltage value and still not cause the
|               input to switch.  Pulse_time is required for pulse immunity
|               testing.  A rising response is tested only if Pulse_high is
|               specified.  Similarly, a falling response is tested only if
|               Pulse_low is specified.  The rising response may exceed the
|               Vinl value, but remain below the Pulse_high value.
|
|               Similarly, the falling response may drop below the Vinh value,
|               but remain above the Pulse_low value.  In either case the
|               input is regarded as immune to switching if the responses
|               are within these extended windows.  If the hysteresis
|               thresholds are defined, then the rising response shall use
|               Vinh- as the reference voltage, and the falling response shall
|               use Vinl+ as the reference voltage.
|
|         |
|         |         Receiver Voltage with Pulse Immunity Thresholds
|         |
|         |
|         |            Switching                           No Switching
|         |                |                               |
|         |                |      oo    o                  |  Switching
|         |                |    o    oo  ooooooooo         |      |
|         |                |   o                    o      |      | 
|         |                V  o                       o    V   oooV
|  Vinh - - - - - - - - - -  x - - - - - - - - - - - - - x   o + -x
|         | Pulse_time ->|  o  |<-                       |ooo  |   o
|  Pulse_high - - - - -  + o - +            Pulse_low  - + - - +    o   
|         |              |o    |            Pulse_time ->|     |<-   o       
|  Vinl - - - - - - - -  x     + - - - - - - - - - - - - - - - - - -  x
|         |             o                                              o
|         |           o                                                 o
|         |        o                                                      o
|         |oooooo------------------------------------------------------------o
|
|                                       Time -->
|
|               Vmeas, Vref, Cref, Rref rules:
|  
|               The Vmeas, Vref, Cref and Rref values under the [Model Spec]
|               keyword override their respective values entered elsewhere.
|               Note that a Vmeas, Vref, Cref or Rref subparameters may not be
|               used if its edge specific version (*_rising or *_falling) is
|               used.
|  
|               Cref_rising, Cref_falling, Rref_rising, Rref_falling,
|               Vref_rising, Vref_falling, Vmeas_rising, Vmeas_falling rules:
|  
|               Use these subparameters when specifying separate timing test
|               loads and voltages for rising and falling edges.  If one
|               'rising' or 'falling' subparameter is used, then the
|               corresponding 'rising' or 'falling' subparameter must be
|               present.  The values listed in these subparameters override 
|               any corresponding Cref, Vref, Rref or Vmeas values entered
|               elsewhere.
|
|               Rref_diff, Cref_diff rules:
| 
|               The Rref_diff and Creff_diff values under the [Model Spec]
|               keyword override their respective values entered elsewhere.
|               These subparameters are used only when the model is referenced
|               by the [Diff Pin] keyword.  These follow the same rules as
|               the corresponding subparameters documented under the [Model]
|               keyword.  See Section 6b for more discussion on true and
|               single-ended differential operation.
|-----------------------------------------------------------------------------
[Model Spec]
|   Subparameter          typ        min        max
|
| Thresholds
|
Vinh                      3.5        3.15       3.85    | 70% of Vcc
Vinl                      1.5        1.35       1.65    | 30% of Vcc
|
| Vinh                    3.835       3.335     4.335   | Offset from Vcc
| Vinl                    3.525       3.025     4.025   | for PECL
|
| Hysteresis
|
Vinh+                     2.0        NA         NA      | Overrides the
Vinh-                     1.6        NA         NA      | thresholds
Vinl+                     1.1        NA         NA 
Vinl-                     0.6        NA         NA      | All 4 are required
|
| Overshoot
|
S_overshoot_high          5.5        5.0        6.0     | Static overshoot
S_overshoot_low          -0.5        NA         NA
D_overshoot_high          6.0        5.5        6.5     | Dynamic overshoot
D_overshoot_low          -1.0       -1.0       -1.0     | requires
|                                                       | D_overshoot_time 
D_overshoot_time          20n        20n        20n     | & static overshoot
|
| Pulse Immunity
|
Pulse_high                3V         NA         NA      | Pulse immunity
Pulse_low                 0          NA         NA      | requires
Pulse_time                3n         NA         NA      | Pulse_time
|
| Timing Thresholds
|
Vmeas                     3.68       3.18       4.68    | A 5 volt PECL
|                                                       | example
|
| Timing test load voltage reference example
|
Vref                      1.25       1.15       1.35    | An SSTL-2 example
|
|
| Rising and falling timing test load example (values from PCI-X
| specification)
|
Cref_falling              10p        10p         10p
Cref_rising               10p        10p         10p
Rref_rising               25         500         25  | typ value not specified
Rref_falling              25         500         25  | typ value not specified
Vref_rising               0          1.5         0     
Vref_falling              3.3        1.5         3.6   
Vmeas_rising              0.941      0.885       1.026 | vmeas = 0.285(vcc)
Vmeas_falling             2.0295     1.845       2.214 | vmeas = 0.615(vcc)
|   
| Differential timing test load for true or single-ended differential model
| 
Rref_diff                 100        90         110
Cref_diff                 5pF        NA         NA
|
|*****************************************************************************
|* END ORIGINAL TEXT
|*****************************************************************************

|*****************************************************************************
|* NEW TEXT
|*****************************************************************************
|=============================================================================
|     Keyword:  [Model Spec]
|    Required:  No
|  Sub-Params:  Vinh, Vinl, Vinh+, Vinh-, Vinl+, Vinl-, S_overshoot_high,
|               S_overshoot_low, D_overshoot_high, D_overshoot_low,
|*               D_overshoot_time, D_overshoot_area_h, D_overshoot_area_l, 
|*               D_overshoot_ampl_h, D_overshoot_ampl_l, Pulse_high, Pulse_low,
|*               Pulse_time, Vmeas, Vref, Cref, Rref, Cref_rising, Cref_falling,
|*               Rref_rising, Rref_falling, Vref_rising, Vref_falling, 
|*               Vmeas_rising, Vmeas_falling, Rref_diff, Cref_diff
|               
| Description:  The [Model Spec] keyword defines four columns under which
|               specification subparameters are defined.  
|               
|               The following subparameters are defined:
|               Vinh               Input voltage threshold high
|               Vinl               Input voltage threshold low
|               Vinh+              Hysteresis threshold high max Vt+
|               Vinh-              Hysteresis threshold high min Vt+
|               Vinl+              Hysteresis threshold low max Vt-
|               Vinl-              Hysteresis threshold low min Vt-
|               S_overshoot_high   Static overshoot high voltage
|               S_overshoot_low    Static overshoot low voltage
|               D_overshoot_high   Dynamic overshoot high voltage
|               D_overshoot_low    Dynamic overshoot low voltage
|               D_overshoot_time   Dynamic overshoot time
|*               D_overshoot_area_h  Dynamic overshoot high area (in V-s)
|*               D_overshoot_area_l  Dynamic overshoot low area (in V-s)
|*               D_overshoot_ampl_h  Dynamic overshoot high max amplitude
|*               D_overshoot_ampl_l  Dynamic overshoot low max amplitude
|               Pulse_high         Pulse immunity high voltage
|               Pulse_low          Pulse immunity low voltage
|               Pulse_time         Pulse immunity time
|               Vmeas              Measurement voltage for timing measurements
|               Vref               Timing specification test load voltage
|               Cref               Timing specification capacitive load
|               Rref               Timing specification resistance load
|               Cref_rising        Timing specification capacitive load for
|                                  rising edges
|               Cref_falling       Timing specification capacitive load for
|                                  falling edges
|               Rref_rising        Timing specification resistance load for
|                                  rising edges
|               Rref_falling       Timing specification resistance load for
|                                  falling edges
|               Vref_rising        Timing specification test load voltage for
|                                  rising edges
|               Vref_falling       Timing specification test load voltage for
|                                  falling edges
|               Vmeas_rising       Measurement voltage for rising edge timing
|                                  measurements
|               Vmeas_falling      Measurement voltage for falling edge timing
|                                  measurements
|               Rref_diff          Timing specification differential
|                                  resistance load
|               Cref_diff          Timing specification differential
|                                  capacitive load
|
| Usage Rules:  [Model Spec] must follow all other subparameters under the 
|               [Model] keyword.
|
|               For each subparameter contained in the first column, the 
|               remaining three hold its typical, minimum and maximum values.
|               The entries of typical, minimum and maximum must be placed on
|               a single line and must be separated by at least one white
|               space.  All four columns are required under the [Model Spec]
|               keyword.  However, data is required only in the typical
|               column.  If minimum and/or maximum values are not available,
|               the reserved word "NA" must be used indicating the typical
|               value by default.
|
|               The minimum and maximum values are used for specifications
|               subparameter values that may track the min and max operation
|               conditions of the [Model].  Usually it is related to the
|               Voltage Range settings.
|
|               Unless noted below, no subparameter requires having present
|               any other subparameter.
|      
|               Vinh, Vinl rules:
| 
|               The threshold subparameter lines provide additional min and
|               max column values, if needed.  The typ column values are still
|               required and would be expected to override the Vinh and Vinl
|               subparameter values specified elsewhere.  Note: the syntax
|               rule that require inserting Vinh and Vinl under models remains
|               unchanged even if the values are defined under the [Model
|               Spec] keyword.
|
|               Vinh+, Vinh-, Vinl+, Vinl- rules:
|
|               The four hysteresis subparameters (used for Schmitt trigger
|               inputs for defining two thresholds for the rising edges and
|               two thresholds for falling edges) must all be defined before
|               independent input thresholds for rising and falling edges of
|               the hysteresis threshold rules become effective.  Otherwise
|               the standard threshold subparameters remain in effect.  The
|               hysteresis thresholds shall be at the Vinh+ and Vinh- values
|               for a low-to-high transition, and at the Vinl+ and Vinl-
|               values for a high-to-low transition.
|
|         |
|         |           Receiver Voltage with Hysteresis Thresholds
|         |
|         |
|         |       Rising Edge                            Falling Edge
|         |    Switching Region   oo    o              Switching Region
|         |                  |  o    oo  ooooooooo           |
|         |                  V o                    o        |
|  Vinh+  - - - - - - - - - - x                        o     |
|  Vinh-  - - - - - - - - -  x                           o   |
|         |                 o                             o  |
|         |                o                               o |
|         |               o                                 oV
|  Vinl+  - - - - - - -  o - - - - - - - - - - - - - - - - - x
|  Vinl-  - - - - - - - o  - - - - - - - - - - - - - - - - -  x
|         |           o                                         o
|         |        o                                               o
|         |oooooo-----------------------------------------------------oooooooo
|
|                                       Time -->
|
|               S_overshoot_high, S_overshoot_low rules:
|
|               The static overshoot subparameters provide the DC voltage
|               values for which the model is no longer guaranteed to function
|               correctly.  Typically these are voltages that would cause the
|               physical component to be destroyed.
|
|               D_overshoot_high, D_overshoot_low, D_overshoot_time rules:
|
|               The dynamic overshoot values provide a time window during
|               which the overshoot may exceed the static overshoot limits
|               but be below the dynamic overshoot limits.  D_overshoot_time
|               is required for dynamic overshoot testing.  In addition, if
|               D_overshoot_high is specified, then S_overshoot_high is
|               necessary for testing beyond the static limit.  Similarly, if
|               D_overshoot_low is specified, then S_overshoot_low is
|               necessary for testing beyond the static limit.
|                
|         |
|         |     Receiver Voltage with Static and Dynamic Overshoot Limits
|         |
|         |
|         |   D_overshoot_time ->|      |<-
|         |                      |      |
|  D_overshoot_high - - - - - - -+ - - -+                       
|         |                      | oo   |  Passes - Does Not Exceed Bounds
|         |                      |o  o  |
|  S_overshoot_high - - - - - - -x    o +- - - - - - - - - - - - - - - - - - -
|         |                     o      o ooooooooo 
|         |                    o        o         o
|         |                   o                    o
|         |                  o                      o
|         |                 o                        o
|         |                o                          o
|         |               o                            o
|         |              o                              o        Fails -
|         |             o                                o    Exceeds Bounds
|         |           o                                   o      |   |  |
|         |        o                                       o     V   V  V
|         |oooooo-------------------------------------------o---------o---oooo
|  S_overshoot_low - - - - - - - - - - - - - - - - - - - - - x      +x x x - -
|         |                                                  |o     x   x
|         |                                                  | o   o|
|  D_overshoot_low - - - - - - - - - - - - - - - - - - - - - + -x x-+
|         |                                                  |   x  |
|                                         D_overshoot_time ->|      |<-
|
|                                       Time -->
|
|*               D_overshoot_area_h, D_overshoot_area_l, D_overshoot_ampl_h,
|*               D_overshoot_ampl_l rules:
|*
|*               The dynamic overshoot area values define a maximum V-s
|*               area that an overshooting signal must not exceed.  The high
|*               area is calculated from the point that a signal overshoots
|*               above the voltage defined by the [Power Clamp Reference] 
|*               keyword until the point that the signal crosses back through
|**              this same voltage.  Note that the area is defined as the
|**              complete area-under-the-curve as bounded by the limits defined
|**              above and not a "triangular" area as shown in the example
|**              drawing below.  If [Power Clamp Reference] is not defined,  
|*               then this crossing voltage is assumed to be defined
|*               by the [Voltage Range] keyword.  The low area is calculated
|*               from the point that a signal overshoots below the voltage 
|*               defined by the [GND Clamp Reference] keyword until the point
|*               that the signal crosses back through this same voltage.  If
|*               [GND Clamp Reference] is not defined, then this crossing
|*               voltage is assumed to be 0.0 V.  If D_overshoot_area_h is
|*               specified, then D_overshoot_ampl_h must also be specified. 
|*               D_overshoot_ampl_h provides a maximum amplitude allowed for
|*               the overshoot area and is measured as voltage above the
|*               [Power Clamp Reference] voltage.  Similarly, if 
|*               D_overshoot_area_l is specified, then D_overshoot_ampl_l must
|*               also be specified.  D_overshoot_ampl_l is measured as voltage
|*               below the [GND Clamp Reference] voltage.  Both amplitude 
|*               parameters should be listed as absolute (non-negative) values.
|*               Also, if D_overshoot_area_h, D_overshoot_area_l,
|*               D_overshoot_ampl_h, and D_overshoot_ampl_l are specified, then 
|*               other static and dynamic overshoot parameters are optional.               
|
|*         |
|*         |     Receiver Voltage with Dynamic Area Overshoot Limits
|*         |
|*         |
|*         |     
|*         |
|*  D_overshoot_ampl_h  - - - - - - ++- - - - - - - - - - - - - - - - - - - -                        
|*  D_overshoot_area_h - - - - - ->/o \  <--Passes - Does Not Exceed Overshoot
|*         |                      /o o \             Area nor Amplitude
|*  [Power Clamp Reference] - - --o   o - - - - - - - - - - - - - - - - - - -
|*         |                     o     o 
|*         |                    o       o oooooo
|*         |                   o         o      o
|*         |                  o                  o
|*         |                 o                    o
|*         |                o                      o
|*         |               o                        o  Fails - Exceeds
|*         |              o                          o  Overshoot Area
|*         |             o                            o  and Amplitude
|*         |           o                               o     |       o
|*         |oooooooooo                                  o    |      o o oooo
|*         |                                             o   V     o   o
|* [GND Clamp Reference] - - - - - - - - - - - - - - - - -o     - o - - - -
|*         |                                              \o   / x
|*  D_overshoot_area_l - - - - - - - - - - - - - - - - - ->\o / x
|*  D_overshoot_ampl_l - - - - - - - - - - - - - - - - - - -+x x - - - - - - 
|*         |                                                  x   
|*
|*                                       Time -->
|
|               Pulse_high, Pulse_low, Pulse_time rules:
|
|               The pulse immunity values provide a time window during which
|               a rising pulse may exceed the nearest threshold value but
|               be below the pulse voltage value and still not cause the
|               input to switch.  Pulse_time is required for pulse immunity
|               testing.  A rising response is tested only if Pulse_high is
|               specified.  Similarly, a falling response is tested only if
|               Pulse_low is specified.  The rising response may exceed the
|               Vinl value, but remain below the Pulse_high value.
|
|               Similarly, the falling response may drop below the Vinh value,
|               but remain above the Pulse_low value.  In either case the
|               input is regarded as immune to switching if the responses
|               are within these extended windows.  If the hysteresis
|               thresholds are defined, then the rising response shall use
|               Vinh- as the reference voltage, and the falling response shall
|               use Vinl+ as the reference voltage.
|
|         |
|         |         Receiver Voltage with Pulse Immunity Thresholds
|         |
|         |
|         |            Switching                           No Switching
|         |                |                               |
|         |                |      oo    o                  |  Switching
|         |                |    o    oo  ooooooooo         |      |
|         |                |   o                    o      |      | 
|         |                V  o                       o    V   oooV
|  Vinh - - - - - - - - - -  x - - - - - - - - - - - - - x   o + -x
|         | Pulse_time ->|  o  |<-                       |ooo  |   o
|  Pulse_high - - - - -  + o - +            Pulse_low  - + - - +    o   
|         |              |o    |            Pulse_time ->|     |<-   o       
|  Vinl - - - - - - - -  x     + - - - - - - - - - - - - - - - - - -  x
|         |             o                                              o
|         |           o                                                 o
|         |        o                                                      o
|         |oooooo------------------------------------------------------------o
|
|                                       Time -->
|
|               Vmeas, Vref, Cref, Rref rules:
|  
|               The Vmeas, Vref, Cref and Rref values under the [Model Spec]
|               keyword override their respective values entered elsewhere.
|               Note that a Vmeas, Vref, Cref or Rref subparameters may not be
|               used if its edge specific version (*_rising or *_falling) is
|               used.
|  
|               Cref_rising, Cref_falling, Rref_rising, Rref_falling,
|               Vref_rising, Vref_falling, Vmeas_rising, Vmeas_falling rules:
|  
|               Use these subparameters when specifying separate timing test
|               loads and voltages for rising and falling edges.  If one
|               'rising' or 'falling' subparameter is used, then the
|               corresponding 'rising' or 'falling' subparameter must be
|               present.  The values listed in these subparameters override 
|               any corresponding Cref, Vref, Rref or Vmeas values entered
|               elsewhere.
|
|               Rref_diff, Cref_diff rules:
| 
|               The Rref_diff and Creff_diff values under the [Model Spec]
|               keyword override their respective values entered elsewhere.
|               These subparameters are used only when the model is referenced
|               by the [Diff Pin] keyword.  These follow the same rules as
|               the corresponding subparameters documented under the [Model]
|               keyword.  See Section 6b for more discussion on true and
|               single-ended differential operation.
|-----------------------------------------------------------------------------
[Model Spec]
|   Subparameter          typ        min        max
|
| Thresholds
|
Vinh                      3.5        3.15       3.85    | 70% of Vcc
Vinl                      1.5        1.35       1.65    | 30% of Vcc
|
| Vinh                    3.835       3.335     4.335   | Offset from Vcc
| Vinl                    3.525       3.025     4.025   | for PECL
|
| Hysteresis
|
Vinh+                     2.0        NA         NA      | Overrides the
Vinh-                     1.6        NA         NA      | thresholds
Vinl+                     1.1        NA         NA 
Vinl-                     0.6        NA         NA      | All 4 are required
|
| Overshoot
|
S_overshoot_high          5.5        5.0        6.0     | Static overshoot
S_overshoot_low          -0.5        NA         NA
D_overshoot_high          6.0        5.5        6.5     | Dynamic overshoot
D_overshoot_low          -1.0       -1.0       -1.0     | requires
|                                                       | D_overshoot_time 
D_overshoot_time          20n        20n        20n     | & static overshoot
|
|* Overshoot defined by area in V-s (Values from DDR2 specification)
|*
D_overshoot_ampl_h        0.9        NA         NA      | Dynamic overshoot
D_overshoot_ampl_l        0.9        NA         NA      | requires area
D_overshoot_area_h        0.38n      NA         NA      | and amplitude
D_overshoot_area_l        0.38n      NA         NA      | parameters 
|* 
| Pulse Immunity
|
Pulse_high                3V         NA         NA      | Pulse immunity
Pulse_low                 0          NA         NA      | requires
Pulse_time                3n         NA         NA      | Pulse_time
|
| Timing Thresholds
|
Vmeas                     3.68       3.18       4.68    | A 5 volt PECL
|                                                       | example
|
| Timing test load voltage reference example
|
Vref                      1.25       1.15       1.35    | An SSTL-2 example
|
|
| Rising and falling timing test load example (values from PCI-X
| specification)
|
Cref_falling              10p        10p         10p
Cref_rising               10p        10p         10p
Rref_rising               25         500         25  | typ value not specified
Rref_falling              25         500         25  | typ value not specified
Vref_rising               0          1.5         0     
Vref_falling              3.3        1.5         3.6   
Vmeas_rising              0.941      0.885       1.026 | vmeas = 0.285(vcc)
Vmeas_falling             2.0295     1.845       2.214 | vmeas = 0.615(vcc)
|   
| Differential timing test load for true or single-ended differential model
| 
Rref_diff                 100        90         110
Cref_diff                 5pF        NA         NA
|
|*****************************************************************************
|* END NEW TEXT
|*****************************************************************************

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

ANALYSIS PATH/DATA THAT LED TO SPECIFICATION

While creating DDR2 SDRAM IBIS models, it was found that the AC Overshoot/
Undershoot specification could not be checked accurately by simulation tools
given the parameters available for defining overshoot and undershoot under
the [Model Spec] keyword.  The DDR2 specification defines overshoot and
undershoot in terms of a V-ns area.  It was determined that adding two 
parameters to [Model Spec] to describe this area would give EDA software the
necessary information to check for violations of the specification.

The DDR2 specification also defines the maximum amplitude for overshoot.  This
amplitude is measured from the VDD/VDDQ and VSS/VSSQ levels.  Adding two
amplitude parameters to [Model Spec] allows for checking of this violation as
well.  The amplitude parameters are defined as positive values above or below
the VDD/VDDQ and VSS/VSSQ levels in the DDR2 specification, so they are defined
the same way in this BIRD.

For more information on the DDR2 Overshoot/Undershoot specification, refer to 
the JEDEC document JESD79-2B available at the following url:

http://www.jedec.org/download/search/JESD79-2b.pdf
  

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ANY OTHER BACKGROUND INFORMATION:


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