Subject: [IBIS] Bird 74.1 EMI Parameters for IBIS
From: Guy deBurgh (gdeburgh@innoveda.com)
Date: Fri May 31 2002 - 14:21:56 PDT
To the IBIS committee.
BIRD 74 has been updated. Briefly the changes are:
1) Iccd parameter removed as it can be converted to Cpd. Base units
of mA/MHz removed.
2) Die_Height and Heatsink parameters removed as they are physical,
not electrical, parameters. Base units of m (meter) removed.
3) Added section 1.3 [Pin Mapping EMI] and 1.4 [Pin Domain EMI].
These define the power used by each clock domain.
4) Added "shielded_pwr" to [Model EMI] to identify the return path.
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BIRD ID#: 74.1
ISSUE TITLE: EMI Parameters
REQUESTER: Guy de Burgh, Innoveda
DATE SUBMITTED: March 19, 2002
DATE ACCEPTED BY IBIS OPEN FORUM: Pending
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STATEMENT OF THE ISSUE:
Additional parameters required for EMI analysis.
All these parameters are optional.
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STATEMENT OF THE RESOLVED SPECIFICATIONS:
The following changes are proposed:
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Changes and additions to the IBIS Specification are shown by the |* lines.
Examples are shown as they would be seen in a specification.
All of these changes and additions are optional.
1) Keyword additions to Section 5 Component Description.
1.1) Component EMI
|===========================================================================
==
|* Keyword: [Component EMI]
|* Required: No
|*Description: Specifies the EMI parameters for a Component.
|* Sub-Params: Component_type, Domain, Family, Cpd
|*
|*Usage Rules: Component_type indicates whether the component is a
|* connector. This identifies I/O signals (which act as
monopole
|* antennas).
|* It is one of:
|* Active, Connector
|* If not entered the default is Active.
|*
|* Domain indicates whether the component is a digital, analog
|* or part digital part analog. Analog circuits are more
|* susceptible to low-level noise. Analog circuits operate at
very
|* low signal levels (mV or uV) and can contain high gain
|* amplifiers. In contrast, digital circuits operate at
|* relatively large signal levels (compared to analog
circuits).
|* It is one of:
|* Digital, Analog, Digital_analog
|* If not entered the default is Digital.
|*
|* Family describes the logic family of the component.
|* This parameter is used so that reasonable assumptions about
|* missing information can be made when an incomplete model
|* specification is used.
|* Missing information:
|* Input impedance
|* Source impedance
|* Maximum transient switching current
|* Even if this information is already available the logic
family
|* adds extra information. For example, unused floating inputs
on
|* a high input impedance device is likely to pick up noise.
|* In addition, if the device is CMOS, an unused gate whose
inputs
|* are floating may bias itself into the linear region. This
will
|* increase the dc current drawn by the circuit.
|* It is one of:
|* UNDEF, TTL, CMOS, ECL
|* TTL, CMOS, and ECL can be used in a similar manner as that
just
|* described for CMOS. UNDEF is used to disable any family
|* specific algorithms.
|* If not entered the default is UNDEF.
|*
|* Cpd is the power dissipation capacitance parameter.
|* It is typically for CMOS devices, and helps provide a more
|* accurate estimation of the power bus current, and therefore
the
|* noise voltage on the power bus. Knowing the high frequency
|* noise on the power bus (due to switching of digital
circuits)
|* the radiation can be calculated.
|* Sometimes Iccd (Dynamic power supply current) is found in
|* databooks. It is normally given for FACT families. Cpd can
be
|* calculated from Iccd by the equation Cpd = Iccd / Vcc.
|* The syntax for Cpd is:
|* cpd
|* Cpd (Power Dissipation Capacitance) is the internal
parasitic
|* capacitance (e.g., gate-to-source and gate-to-drain
capacitance)
|* plus the equivalent capacitance associated with the through
|* currents when both transistors (n-channel and p-channel) are
|* momentarily conducting.
|* The units are Farads.
|*
|---------------------------------------------------------------------------
-- [Component] ecl_component . . . [Component EMI] Component_type Active Domain Digital Family ECL Cpd 6.4pF | |=========================================================================== ==1.2) Pin EMI
|=========================================================================== == |* Keyword: [Pin EMI] |* Required: No |*Description: Specifies the EMI parameters for a Pin. |* This is only used when the component is a connector. |* Sub-Params: cspec_name |*Usage Rules: Each line must contain two columns. |* The first column must contain the pin name. This pin name |* must match a pin name in the [Pin] keyword. (The pin name |* is the first column in the [Pin] record.) |* The cspec_name represents a user definable specification |* name that must have a corresponding model name listed in the |* [Model EMI] keyword. |* |* Column length limits are: |* pin_name 5 characters max |* cspec_name 20 characters max |--------------------------------------------------------------------------- -- [Pin EMI] cspec_name | 1 unshielded 4 a_pin 10 grounded
1.3) Pin Mapping EMI
|=========================================================================== == |* Keyword: [Pin Mapping EMI] |* Required: No |*Description: Specifies the domain name of each clock domain. |* Sub-Params: domain_name |*Usage Rules: Each line must contain two columns. |* The first column must contain the pin name. This pin name |* must match a pin name in the [Pin] keyword. (The pin name |* is the first column in the [Pin] record.) |* The second column is the domain name. |* |* Column length limits are: |* pin_name 5 characters max |* domain_name 20 characters max |--------------------------------------------------------------------------- -- [Pin Mapping EMI] domain_name | 1 CPU 4 MEM 5 MEM 10 RIOG
1.4) Pin Domain EMI
|=========================================================================== == |* Keyword: [Pin Domain EMI] |* Required: No |*Description: Specifies the percentage of power used in each clock domain. |* Sub-Params: percentage |*Usage Rules: Each line must contain two columns. |* The first column must contain the domain_name. This name |* must match a domain name in the [Pin Mapping EMI] keyword. |* (The domain name is the first column in that record.) |* The percentage represents a user definable percentage of the |* power used by that domain. |* |* Column length limits are: |* domain_name 20 characters max |* percentage 5 characters max |--------------------------------------------------------------------------- -- [Pin Domain EMI] percentage | CPU 40 MEM 30 RIOG 30
3) Keyword additions to Section 6 Model Statement.
|=========================================================================== == |* Keyword: [Model EMI] |* Required: No |*Description: Used to define EMI parameters for a model. |* Sub-Params: Model_emi_type, Domain, Con_spec |*Usage Rules: Each model type must begin with the keyword [Model EMI]. The |* model name must match the one that is listed under a cspec_name |* in [Pin EMI], |* |* Model_emi_type can only be set to ferrite. This indicates |* that the model is a ferrite. If not entered (the default) |* the model is not a ferrite. |* |* Domain indicates whether the model is a digital or analog. |* It is one of: |* Digital, Analog |* This is only required if the [Component EMI] Domain is set to |* Digital_analog. |* If not entered the default is to use the [Component EMI] Domain |* setting and its default. |* |* Con_spec indicates whether the pin is unshielded (normally |* connected), shielded (ground pins provide shield), |* shielded_pwr (power pins provide shield), |* con_to_shield (pin connected to connector shell), or |* has a ferrite filter. |* In addition the pin can have explicit filter capacitance. |* These are used to calculate an antenna impedance for the pin. |* The syntax is: |* Con_spec attribute filter_cap |* where attribute is one of: |* unshielded, shielded, shielded_pwr, con_to_shield, ferrite |* and filter_cap is the filter capacitance in Farads. |* filter_cap is optional and is should be set to NA if not used. |--------------------------------------------------------------------------- -- [Model EMI] grounded Con_spec shielded 7.0pF
[Model EMI] a_pin Model_emi_type ferrite
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ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:
EMI is becoming increasingly important in PCB design. EMI simulation is not an exact science. The problem is too complicated for today's computers. However being able to identify which signals radiate more than others (relatively), and showing where the energy flows in a system does help in identifying potential EMI problems. No longer requiring absolute accuracy, but requiring relative accuracy, makes the analysis considerably easier, and possible. The parameters specified here are chosen for that purpose, and have been specifically chosen as they are readily available in data books in order to make it easier to create models.
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ANY OTHER BACKGROUND INFORMATION:
Presentations on this topic were given at the IBIS Summit Meeting at DAC on June 21, 2001, and at DesignCon on January 28, 2002.
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