Subject: [IBIS] BIRD74.4
From: deBurgh, Guy (guy_deburgh@mentorg.com)
Date: Wed May 21 2003 - 09:36:04 PDT
To the IBIS Committee.
BIRD 74 has been updated. Briefly the changes are:
1) Removed "Signal Swing" keyword.
2) Removed Connector related information.
This will now be proposed as a change to the Connector Spec.
3) Corrected [Begin EMI Model] syntax.
4) Simplified the [Begin EMI Model] section.
5) Added a parameter to Heatsink to indicate whether it is floating
or grounded.
6) Heatsink References:
[1] "Grounding of Heatpipe/Heatspreader and Heatsink Structures for EMI
Mitigation" by C. Wang, J.L. Drewniak, J.L. Knighten, D. Wang,
R. Alexander, D.M. Hockanson. (Electromagnetic Compatibility, 2001.
2001 IEEE International Symposium on EMC, volume 2, pp 916-920.)
[2] "Investigation of Fundamental EMI Source Mechanisms Driving Common-Mode
Radiation from Printed Circuit Boards with Attached Cables" by
D.M. Hockanson, J.L. Drewniak, T.H. Hubing, T.P. Van Doren, F. Sha,
M.J. Wilhelm. (IEEE transactions on Electromagnetic Compatibility,
Vol 38, No. 4, November 1996.)
[3] "PCB Design for Real-World EMI Control" by Bruce Archambeault.
Paragraph 4.5 "Grounding Heatsinks to PC boards".
2002 Kluwer Academic Publishers.
Guy de Burgh
Mentor Graphics
****************************************************************************
**
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**
BIRD ID#: 74.4
ISSUE TITLE: EMI Parameters
REQUESTER: Guy de Burgh, Mentor Graphics
DATE SUBMITTED: May 21, 2003
DATE ACCEPTED BY IBIS OPEN FORUM: Pending
****************************************************************************
**
****************************************************************************
**
STATEMENT OF THE ISSUE:
Additional parameters required for EMI analysis.
All these parameters are optional.
****************************************************************************
**
STATEMENT OF THE RESOLVED SPECIFICATIONS:
The following changes are proposed:
****************************************************************************
**
Changes and additions to the IBIS Specification are shown by the |* lines.
Examples are shown as they would be seen in a specification.
|===========================================================================
==
|===========================================================================
==
|
| Section 10
|
| E M I P A R A M E T E R S
|
|===========================================================================
==
|
| There are two sections here: one for a [Component] and one for a [Model].
|
|===========================================================================
==
|===========================================================================
==
|
| This section describes the structure of the EMI parameters under a
| top-level [Component] keyword. It is used to describe the EMI parameters
| associated with a [Component]. The parameters must be surrounded by
| the [Begin EMI Component] and [End EMI Component] keywords.
|
| The following set of keywords are defined:
|
| [Begin EMI Component]
| [End EMI Component]
| [Domain]
| [Cpd]
| [Heatsink_cap]
| [Pin EMI]
| [Pin Domain EMI]
|
|===========================================================================
==
|
| Keyword: [Begin EMI Component]
| Required: No
| Description: Marks the beginning of the Component EMI parameters.
| Sub-Params: Domain, Cpd, Heatsink_cap
|
|===========================================================================
==
|
| Keyword: [Domain]
| Required: No
| Description: 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).
|
| Usage Rules: It is one of:
| Digital, Analog, Digital_analog
|
| If not entered the default is Digital.
|
|===========================================================================
==
|
| Keyword: [Cpd]
| Required: No
| Description: Cpd is the power dissipation capacitance parameter.
| 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.
|
| 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.
|
| Usage Rules: The syntax for Cpd is:
| Cpd
|
| The units are Farads.
|
| If not entered the default is 0.0F.
|
|===========================================================================
==
|
| Keyword: [Heatsink_cap]
| Required: No
| Description: Internal currents inside a (high speed) IC can be closely
| coupled onto a heatsink. As the heatsink is physically much
| larger than the IC silicon chip and bond wires it is a more
| efficient radiator. Knowing the capacitance of the heatsink
| the radiated electric field can be estimated.
| If this parameter is defined then a heatsink is present.
| If this parameter is not defined then the component does not
| have a heatsink.
| The keyword takes two arguments: the heatsink capacitance,
and
| whether the heatsink is grounded (or not).
|
| Usage Rules: The syntax for Heatsink_cap is:
| Heatsink_cap Grounded
|
| The units for Heatsink_cap are Farads.
| The units for Grounded are boolean. GND => the heatsink is
| grounded. FLOAT => the heatsink is floating.
|
| If this keyword is not entered the default is that the
| component does not have a heatsink.
|
|===========================================================================
==
|
| Example:
|
[Component] ecl_component
.
.
.
[Begin EMI Component]
Domain Digital
Cpd = 6.4pF
Heatsink_cap 3.4pF GND
[End EMI Component]
|
|===========================================================================
==
|
| Keyword: [Pin EMI]
| Required: No
| Description: Specifies the EMI parameters for a Pin.
| Sub-Params: domain_name, clock_div
| Usage Rules: Each line must contain three 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. This specifies the
clock
| domain for that pin. This is used by [Pin Domain EMI].
| The field can be left blank, or set to NA, if unused.
|
| The third column is the clock division. This is the ratio
| of the frequency at this pin to the reference pin. The
| reference pin is always set to "1.0". The ratio is a
floating
| point number. The choice of the reference in does not matter
| as this information is pin to pin ratios. It is suggested
that
| the pin with the dominant frequency is chosen as the
reference.
| The field can be left blank, or set to NA, if unused.
|
| Column length limits are:
| pin_name 5 characters max
| domain_name 20 characters max
| clock_div 5 characters max
|
|===========================================================================
=
|
| 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 EMI] keyword. (The domain
| name is the second column in that record.)
|
| The percentage represents a user definable percentage of the
| power used by that domain. It is an integer in the range
| 0 < percentage =< 100
|
| Column length limits are:
| domain_name 20 characters max
| percentage 5 characters max
|
|===========================================================================
==
|
| Example:
|
[Component] ecl_component
.
.
.
[Begin EMI Component]
Domain Digital
Cpd = 6.4pF
|
[Pin EMI] domain_name clock_div
1 NA
4 MEM 0.5
5 MEM 0.5
10 NA
14 CPU 1.0
15 RIOG 0.5
|
[Pin Domain EMI] percentage
CPU 40
MEM 30
RIOG 30
|
[End EMI Component]
|
|===========================================================================
==
|===========================================================================
==
|
| This section describes the structure of the EMI parameters under a
| top-level [Model] keyword. It is used to describe the EMI parameters
| associated with a [Model]. The parameters must be surrounded by
| the [Begin EMI Model] and [End EMI Model] keywords.
|
| The following set of keywords are defined:
|
| [Begin EMI Model]
| [End EMI Model]
| [Model_emi_type]
| [Domain]
|
|===========================================================================
==
|
| Keyword: [Begin EMI Model]
| Required: No
| Description: Marks the beginning of the Model EMI parameters.
| Sub-Params: Model_emi_type, Domain
|
|===========================================================================
==
|
| Keyword: [Model_emi_type]
| Required: No
| Description: Indicates that the model (for this pin) is a ferrite.
|
| Usage Rules: Model_emi_type can only be set to Ferrite.
| If not entered (the default) the model is not a ferrite.
|
|===========================================================================
==
|
| Keyword: [Domain]
| Required: No
| Description: Domain indicates whether the model is a digital or analog.
| This is only required if the [Component EMI] Domain is set
to
| Digital_analog.
|
| Usage Rules: It is one of:
| Digital, Analog
|
| If not entered the default is to use the [Component EMI]
| Domain setting and it's default.
|
|===========================================================================
==
|
| Keyword: [End EMI Model]
| Required: No
| Description: Marks the end of the Model EMI parameters.
|
|===========================================================================
==
|
|---------------------------------------------------------------------------
-- | [Model] modelname . . . [Begin EMI Model] Domain Analog Model_emi_type Ferrite [End EMI Model] | **************************************************************************** **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.
**************************************************************************** **
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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