Re: Can't do T-LINE?

Chris:

The L, C, and R parameters are given as CORRESPONDING per unit length values.
These are multiplied by Len to produce the total distributed values for the
exact length of T-line that you want.

Whenever Len is not equal to zero, the section is interpreted as
a distributed section (not a lumped section).

The T-line relationships still hold:

   Zo = sqrt(L/C)
   TD = Len * sqrt(LC)

So the electrical information is available for a T-line of whatever length
you want.

Best Regards,
Bob Ross
Interconnectix/Mentor Graphics

> Sender: crokusek@qdt.com
> Date: Tue, 19 May 1998 17:56:15 -0700
> From: Chris Rokusek <crokusek@viewlogic.com>
> To: ibis@eda.org
> Subject: Can't do T-LINE?

> ( I am reposting this question in hopes of a more helpful response )

> Hi All,

> Concerning [Path Description] section in Ver 3.x of .ibs...

> The 'len' parameter is given in 'units' which is 'arbitrary' (i.e. not
> meters) such that a distributed T-LINE model cannot be built with the
> proper physical length.

> ** I DO NOT WANT TO BUILD A LUMPED MODEL, I WANT TO BUILD A T-LINE MODEL
> **

> Is this an oversight or am I not understanding the parameters?

> Best Regards,

> Chris Rokusek
> Viewlogic Systems

>
>
> |=============================================================================
> | Keyword: [Path Description]
> | Required: Yes
> | Description: This keyword allows the user to describe the connection
> | between the user accessible pins of a part and the pins
> of the
> | ICs mounted on that part. Each pin to node connection
> is
> | divided into one or more cascaded "sections", where each
> | section is described in terms of it's L/R/C per unit
> length.
> | The Fork and Endfork subparameters allow the path to
> branch to
> | multiple nodes, or another pin. A path description is
> | required for each pin whose signal name is not "GND",
> "POWER"
> | or "NC".
> |
> | Board Description and IC Boundaries:
> |
> | In any system, each part interfaces with another part at
> some
> | boundary. Every part model must contain the components
> | necessary to represent the behavior of the part being
> modeled
> | within its boundaries. The boundary definition depends
> upon
> | the parts being represented by the model.
> |
> | For CARD EDGE CONNECTIONS such as a SIMM or a PC
> Daughter
> | Card plugged into a SIMM Socket or Edge Connector, the
> | boundary should be at the end of the board card edge
> pads as
> | they emerge from the connector.
> |
> | For any THROUGH-HOLE MOUNTED PART, the boundary will be
> at the
> | surface of the board on which the part is mounted.
> |
> | SURFACE MOUNTED PART models end at the outboard end of
> their
> | recommended surface mount pads.
> |
> | If the board level component contains an UNMATED
> CONNECTOR,
> | the unmated connector will be described in a separate
> file,
> | with its boundaries being as described above for the
> | through-hole or surface mounted part.
> |
> | Sub-Params: Len, L, R, C, Fork, Endfork, Pin, Node
> | Usage Rules: Each individual connection path (user pin to node(s))
> | description begins with the [Path Description] keyword
> and a
> | path name, followed by the subparameters used to
> describe the
> | path topology and the electrical characteristics of each
> | section of the path. The path name must not exceed 40
> | characters, blanks are not allowed, and each occurrence
> of the
> | [Path Description] keyword must be followed by a unique
> path
> | name. Every signal pin (pins other than POWER, GND or
> NC)
> | must appear in one and only one path description per
> [Begin
> | Board Description]/[End Board Description] pair. Pin
> names do
> | not have to appear in the same order as listed in the
> [Pin
> | List] table. The individual subparameters are broken up
> into
> | those that describe the electrical properties of a
> section,
> | and those that describe the topology of a path.
> |
> | Section Description Subparameters:
> |
> | The Len, L, R, and C subparameters specify the length,
> the
> | series inductance and resistance and the capacitance to
> ground
> | of each section in a path description.
> |
> | Len The physical length of a section. Lengths are
> given
> | in terms of arbitrary 'units'. Any non-zero
> length
> | requires that the parameters that follow must be
> | interpreted as distributed elements by the
> simulator.
> | L The series inductance of a section, in terms of
> | 'inductance/unit length'. For example, if the
> total
> | inductance of a section is 3.0 nH and the length
> of
> | the section is 2 'units', the inductance would
> be
> | listed as L = 1.5 nH (i.e. 3.0 / 2).
> | C The capacitance to ground of a section, in terms
> of
> | capacitance per unit length.
> | R The series DC (ohmic) resistance of a section,
> in
> | terms of ohms per unit length.
> |
> | Topology Description Subparameters:
> |
> | The Fork and Endfork subparameters denote branches from
> the
> | main pin-to-node or pin-to-pin connection path. The
> Node
> | subparameter is used to reference the pin of a component
> or
> | board as defined in a .ibs or .ebd file. The Pin
> subparameter
> | is used to indicate the point at which a path connects
> to a
> | user visible pin.
> |
> | Fork This subparameter indicates that the sections
> | following (up to the Endfork subparameter) are
> part
> | of a branch off of the main connection path.
> This
> | subparameter has no arguments.
> | Endfork This subparameter indicates the end point of a
> branch.
> | For every Fork subparameter there must be a
> | corresponding Endfork subparameter. As with the
> Fork
> | subparameter, the Endfork subparameter has no
> | arguments.
> | Node reference_designator.pin
> | This subparameter is used when the connection
> path
> | connects to a pin of another, externally defined
> part.
> | The arguments of the Node subparameter indicate
> the
> | pin and reference designator of the external
> | component. The pin and reference designator
> portions
> | of the argument are separated by a period
> ("."). The
> | reference designator is mapped to an external
> | component description (another .ebd file or .ibs
> file)
> | by the [Reference Designator Map] Keyword. Note
> that
> | a Node MUST reference a model of a passive or
> active
> | component. A Node is not an arbitrary
> connection
> | point between two elements or paths.
> | Pin This subparameter is used to mark the point at
> which
> | a path description connects to a user accessible
> pin.
> | Every path description must contain at least one
> | occurrence of the Pin subparameter. It may also
> | contain the reserved word NC. The value of the
> Pin
> | subparameter must be one of the pin names listed
> in
> | the [Pin List] section.
> |
> | Using The Subparameters to Describe Paths:
> |
> | A section description begins with the Len subparameter
> and
> | ends with the slash (/) character. The value of the
> Len, L,
> | R, and C subparameters and the subparameter itself are
> | separated by an equals sign (=); whitespace around the
> equals
> | sign is optional. The Fork, Endfork, Node and Pin
> | subparameters are placed between section descriptions
> (i.e.,
> | between the concluding slash of one section and the
> 'Len'
> | parameters that starts another). The arguments of the
> Pin and
> | Node subparameter are separated by white space.
> |
> | Specifying a Len or L/R/C value of zero is allowed. If
> | Len = 0 is specified, then the L/R/C values are the
> total for
> | that section. If a non-zero length is specified, then
> the
> | total L/R/C for a section is calculated by multiplying
> the
> | value of the Len subparameter by the value of the L, R,
> or C
> | subparameter. However, as noted below, if a non-zero
> length
> | is specified, that section MUST be interpreted as
> distributed
> | elements.
> |
> | Legal Subparameter Combinations for Section
> Descriptions:
> |
> | A) Len, and one or more of the L, R and C
> subparameters. If
> | the Len subparameter is given as zero, then the L/R/C
> | subparameters represent lumped elements. If the Len
> | subparameter is non-zero, then the L/R/C subparameters
> | represent distributed elements and both L and C must be
> | specified, R is optional.
> |
> | B) The first subparameter following the [Path
> Description]
> | keyword must be 'Pin', followed by one or more section
> | descriptions. The path description can terminate in a
> Node,
> | another pin or the reserved word, NC.
> |
> | Dealing With Series Elements:
> |
> | A discrete series R or L component can be included in a
> path
> | description by defining a section with L=0 and the
> proper R or
> | L value. A discrete series component can also be
> included in
> | a path description by writing two back to back node
> statements
> | that reference the same component (see the example
> below).
> | Note that both ends of a discrete, two terminal
> component MUST
> | be contained in a single [Path Description]. Connecting
> two
> | separate [Path Description] with a series component is
> not
> | allowed.
> |-----------------------------------------------------------------------------
> |
> | An Example Path For a SIMM Module:
> |
> [Path Description] CAS_2
> Pin J25
> Len = 0.5 L=8.35n C=3.34p R=0.01 /
> Node u21.15
> Len = 0.5 L=8.35n C=3.34p R=0.01 /
> Node u22.15
> Len = 0.5 L=8.35n C=3.34p R=0.01 /
> Node u23.15
> |
> | A Description Using The Fork and Endfork Subparameters:
> |
> [Path Description] PassThru1
> Pin B5
> Len = 0 L=2.0n /
> Len = 2.1 L=6.0n C=2.0p /
> Fork
> Len = 1.0 L = 1.0n C= 2.0p /
> Node u23.15
> Endfork
> Len = 1.0 L = 6.0n C=2.0p /
> Pin A5
> |
> | A Description Including a Discrete Series Element:
> |
> [Path Description] sig1
> Pin B27
> Len = 0 L=1.6n /
> Len = 1.5 L=6.0n C=2.0p /
> Node R2.1
> Node R2.2
> Len = 0.25 L=6.0n C=2.0p /
> Node U25.6
> |
> |=============================================================================
Received on Tue May 19 19:09:14 1998