Fred:
Doesn't this mean that Vout vs. Vin should be measured at speed? That is,
under the same conditions that vout vs. time is measured and tabulated?
ed sayre
=================
At 03:17 PM 8/24/99 -0700, you wrote:
>Stephen Peters wrote:
>>
>> Hello All:
>>
>> As promised, here is the next bird dealing with characterizing
>> and specifying receivers. Comments welcome.
>>
>> Regards,
>> Stephen
>>
>> --------- cut here --------------
>>
>> Buffer Issue Resolution Document (BIRD)
>>
>> BIRD ID#: 62
>> ISSUE TITLE: Enhanced Specification of Receiver Thresholds
>> REQUESTOR: DC Sessions (Philips), Stephen Peters, Richard Melitz,
>> Arpad Muranyi (Intel Corp).
>> DATE SUBMITTED: Aug 24, 1999
>> DATE ACCEPTED BY IBIS OPEN FORUM:
>>
>>
****************************************************************************
***
>>
****************************************************************************
***
>>
>> STATEMENT OF THE ISSUE: When specifying receiver input thresholds the
current
>> specification allows only the traditional DC derived Vinh and Vinl
parameters.
>> These two parameters are no longer adequate for describing receivers
used for
>> high speed designs. This BIRD proposes four new input switching threshold
>> parameters: Vinh_ac, Vinh_dc, Vinl_ac, Vinl_dc. These parameters are
>> referenced to an reference point Vth, and this reference is allowed to vary
>> with variations in a supply.
>>
>>
****************************************************************************
***
>>
>> STATEMENT OF THE RESOLVED SPECIFICATIONS:
>>
>> 1) The following new keyword is defined and placed in the specification
>> just below the [Model Spec] keyword.
>>
>>
|=============================================================================
>> | Keyword: [Receiver Thresholds]
>> | Required: No
>> | Sub-Params: Vth, Vth_min, Vth_max, Vinh_ac, Vinh_dc, Vinl_ac, Vinl_dc,
>> | Vth_sensitivity, Input_Ref_Supply
>> | Description: The [Receiver Thresholds] keyword defines both a set of
>> | receiver input thresholds as well as their sensitivity to
>> | variations in a referenced supply. The subparameters are
>> | defined as follows:
>> |
>> | Vth, Vth_min and Vth_max are the ideal input threshold
voltage
>> | at which the output of a digital logic receiver changes
state.
>> | Vth is the nominal input threshold voltage under the
voltage,
>> | temperature and process conditions that define 'typ'.
Vth_min
>> | is the minimum input threshold voltage at 'typ' conditions
>> | while Vth_max is the maximum input threshold voltage at
'typ'
>> | conditions.
>> |
>> | Vinh_ac is the voltage that a low-to-high going input
waveform
>> | must reach in order to guarantee that the receiver's output
>> | has changed state. In other words, reaching Vinh_ac is
>> | sufficient to guarantee a receiver state change.
Vinh_ac is
>> | expressed as an offset from Vth.
>> |
>> | Vinh_dc is the voltage that an input waveform must remain
>> | above (more positive than) in order to guarantee that a
>> | receiver output will NOT change state. Vinh_dc is
expressed
>> | as an offset from Vth.
>> |
>> | Vinl_ac is the voltage that a high-to-low going input
waveform
>> | must reach in order to guarantee that the receiver's output
>> | has changed state. In other words, reaching Vinl_ac is
>> | sufficient to guarantee a receiver state change. Vinl_ac
>> | is expressed as an offset from Vth.
>> |
>> | Vinl_dc is the voltage that an input waveform must
remain below
>> | (more negative than) in order to guarantee that a
receiver's
>> | output will NOT change state. Vinh_dc is expressed as a
>> | offset from Vth.
>> |
>> | Vth_sensitivity is a unitless number that specifies how Vth
>> | varies with respect to the supply voltage defined by the
>> | Input_Ref_Supply subparameter. Vth_sensitivity is defined
>> | as:
>> |
>> | change in input threshold voltage
>> | Vth_sensitivity = ------------------------------------
>> | change in referenced supply voltage
>> |
>> | Vth_sensitivity must be entered as a number, not as a
>> | fraction.
>> |
>> | Input_Ref_Supply indicates which supply voltage Vth tracks;
>> | i.e. it indicates which supply voltage change causes a
change
>> | in input threshold. The legal arguments to this
subparameter
>> | are VOLTAGE_RANGE (the supply voltage defined by the
>> | [Voltage Range] keyword), PULLUP_REF (the supply voltage
>> | defined by the [Pullup Reference] keyword), or EXT (an
>> | external voltage defined by the [External Reference]
keyword).
>> |
>> |
>> | Usage Rules: The [Receiver Thresholds] keyword is valid if the model
type
>> | includes any reference to input or I/O. The Vinh_ac,
Vinh_dc,
>> | Vinl_ac, Vinh_dc and Vth subparameters are required and
>> | override any threshold subparmeters declared under the
[Model]
>> | or [Model Spec] keywords. The Vth_min, Vth_max,
>> | Vth_sensitivity and Input_Ref_Supply subparameters are
>> | optional. However, if the Vth_sensitivity subparameter is
>> | present then the Input_Ref_Supply subparameter must also be
>> | present.
>> |
>> | Vth at Minimum or Maximum Operating Conditions:
>> | As described above, the Vth_min and Vth_max subparameters
>> | define the minimum and maximum input threshold values under
>> | typical operating conditions. There is no provision for
>> | directly specifying Vth under minimum or maximum operating
>> | conditions. Instead, these values are calculated using
>> | the following equation:
>> |
>> | Vth(new) = Vth(x) + (Vth_sensitivity) X (change in supply
voltage)
>> |
>> | where Vth(x) is either Vth, Vth_min or Vth_max as
appropriate,
>> | and the supply voltage is the one indicated by the
>> | Input_Ref_Supply subparameter.
>> |
>> |
>> | Differential Receivers:
>> | For a single ended receiver the numerical values of Vth,
>> | Vth_min and Vth_max are specified with respect to 0v.
>> | However, if the [Receiver Threshold] keyword is describing
>> | a differential receiver (i.e. is part of a [Model]
statement
>> | that describes a pin listed in the [Diff Pin] keyword),
then
>> | Vth is assigned a value of zero volts and the Vth_min and
>> | Vth_max parameters are not used. The values of Vinh_* and
>> | Vinl_* subparameters are still given as an offset from Vth
>> | and become, in effect, the more traditional Vdiff.
>> |
>> |
>> | Examples:
>> |
>> | A basic 3.3v single ended receiver using only the required
>> | subparameters
>> |
>> Vth = 1.5v
>> Vinh_ac = +225mV
>> Vinh_dc = +100mV
>> Vinl_ac = -225mV
>> Vinl_dc = -100mV
>> |
>> |
>> | A single ended receiver using an external threshold reference. In this
>> | case the input threshold is the external reference voltage so
>> | Vth_sensitivity equals 1.
>> |
>> Vth = 1.0v
>> Vth_sensitivity = 1
>> Input_Ref_Supply = EXT
>> Vinh_ac = +200mV
>> Vinh_dc = +100mV
>> Vinl_ac = -200mV
>> Vinl_dc = -100mV
>> |
>> |
>> | A fully specified single ended 3.3v CMOS receiver
>> |
>> Vth = 1.5v
>> Vth_min = 1.45v
>> Vth_max = 1.53v
>> Vth_sensitivity = 0.45
>> Input_Ref_Supply = VOLTAGE_RANGE
>> Vinh_ac = +200mV
>> Vinh_dc = +100mV
>> Vinl_ac = -200mV
>> Vinl_dc = -100mV
>> |
>> |
>> | A differential receiver
>> |
>> Vth = 0.0v
>> Vinh_ac = +50mV
>> Vinh_dc = +25mV
>> Vinl_ac = -50mV
>> Vinl_dc = -25mV
>>
>> 2) The following new keyword is defined and place in the specification
>> following the [GND Clamp Reference] keyword
>>
|=============================================================================
>> | Keyword: [External Reference]
>> | Required: Yes, if a receiver's input threshold is determined by an
>> | external reference voltage
>> | Description: Defines a voltage source that supplies the reference
voltage
>> | used by a receiver for its input threshold reference.
>> | Usage Notes: Provide actual voltages (not percentages in the typ, min
max
>> | format. "NA" is allowed for the min and max values only.
>>
|-----------------------------------------------------------------------------
>> | variable typ min max
>> [External Reference] 1.0v 0.95v 1.05v
>>
>> 3) Under section 2 of General Syntax Rules and Guidelines the following
>> words are added to the list of reserved words.
>>
>> EXT - A reference to a voltage defined by the [External Reference]
Keyword
>> VOLTAGE_RANGE - A reference to a voltage defined by the [Voltage Range]
keyword
>> PULLUP_REFERENCE - A reference to a voltage defined by the [Pullup
>> Reference] keyword
>>
>>
****************************************************************************
***
>>
>> ANALYSIS PATH/DATA THAT LED TO SPECIFICATION: This proposal follows the
>> recomendations of the JC-15 committee for specifing SDRAM inputs.
>>
>>
****************************************************************************
***
>>
>> ANY OTHER BACKGROUND INFORMATION:
>>
>>
****************************************************************************
***
>I passed some comments to Steven Peters about the general receiver bird.
>Steven thought
>it would be helpful to express those comments on the ibis reflector to
>get feed back. Here is the jest of my comments.
>
>The current bird will require eda vendors to essentially measure slope
>to determine delay. My idea would be to provide device voltage transfer
>information. That is vout as a function of the controlling vin. In this
>way there is no need to specify delay as a function of slope. The delay
>is measured at the output as it attains a high or low. Hystersis
>information can be added as a function of low to high or high to low.
>This may greatly simplify the spec and more importantly make it
>easier for EDA companies to implement.
>
>Comments please.
>
>Best Regards,
>
>--
>Fred Balistreri
>fred@apsimtech.com
>
>http://www.apsimtech.com
>
>
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
| NORTH EAST SYSTEMS ASSOCIATES, INC. |
| ------------------------------------- |
| "High Performance Engineering & Design" |
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
| Dr. Ed Sayre e-mail: esayre@nesa.com |
| NESA, Inc. http://www.nesa.com/ |
| 636 Great Road Tel +1.978.897-8787 |
| Stow, MA 01775 USA Fax +1.978.897-5359 |
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
Received on Tue Aug 24 16:46:56 1999
This archive was generated by hypermail 2.1.8 : Fri Jun 03 2011 - 09:52:30 PDT