Altium Designer PCB仿真教程

SPICE Model Creation from User Data

Summary

This application note provides detailed information on creating and automatically linking a SPICE

simulation model to a schematic component, based on data entered into Altium Designer's SPICE

Model Wizard.

In order to simulate a circuit design using Altium Designer's Mixed- Signal Circuit Simulator, all

components in the circuit need to be simulation-ready

–

that is, they each need to have a linked

simulation model.

The

type

of

model

and

how

it

is

obtained

will

largely

depend

on

the

component

and,

to

some

extent, on the personal preference of the designer. Many device manufacturer's supply simulation

models corresponding to the devices they

manufacture. Typically, it's as simple as downloading

the required model file (SPICE, PSpice?) and hooking it up to the schematic component.

Some

of

the

more

basic

analog

device

models

in

SPICE

require

no

distinct

model

file

–

only

specification of simple parameter values when defining the model link (e.g. Resistor, Capacitor).

Attaching

these

types

of

models

to

a

component

is

straigthforward

and

simply

a

process

of

select-and-enter

(select

the

model

type

and

enter

the

parameter

values

directly

in

an

associated

dialog).

Some models may need to be written from scratch

–

for example using the hierarchical sub-circuit

syntax

to

create

the

required

sub-circuit

model

file

(*.ckt).

Others

–

if

the

device

is

digital

in

nature

–

will require the device to

be modeled using the proprietary Digital SimCode? language,

the definition of which is linked to through an intermediary model file.

Certain analog device models built-in

to SPICE provide for an associated model file (*.mdl)

in

which to parameterically define advanced behavioral characteristics (e.g. Semiconductor Resistor,

Diode,

BJT).

Creation

of

this

model

file

by

hand

and

then

linking

it

manually

to

the

required

schematic

component

can

be

quite

laborious.

Not

anymore

–

enter

Altium

Designer's

SPICE

Model

Wizard.

Using

the

Wizard

the

characetristics

of

such

a

device

can

be

defined

based

on

user- acquired data. The parameters

–

entered either directly or extracted from supplied data

–

are

automatically written to a model file and that file linked to the nominated schematic component.

For

more

information

on

linking

a

model

file,

refer

to

the

Linking

a

Simulation

Model

to

a

Schematic Component

application note.

For detailed information on defining a digital simulation model, refer to the

Creating and Linking

a Digital SimCode Model

application note.

The SPICE Model Wizard

The SPICE Model Wizard provides a convenient, semi-automated solution to creating and linking

a SPICE simulation model for a range of analog devices

–

devices that are built-in to SPICE, and

that require a linked model file (*.mdl). The behavioral characteristics of the model are defined

based

on

information

you

supply

to

the

Wizard.

The

extent

of

this

information

depends

on

the

device type you wish to create a model for

–

ranging from the simple entry of model parameters,

to the entry of device data obtained from a manufacturer's data sheet or by measurements gained

from the physical device itself.

The following sections discuss the use of the Wizard

–

from access to verification.

Accessing the Wizard

The way in which you access the Wizard depends chiefly on how you want to add the required

SPICE model. A model can be added:

?

To a newly created component (created by the Wizard) in a schematic library document

?

To an existing component in a schematic library document

?

To a placed component on a schematic document.

Access in the Schematic Library Editor

If you are unsure of the device you wish to model, access the Wizard by choosing Tools ?

XSpice

Model

Wizard

from

the

main

menus.

By

accessing

the Wizard

in

this

way,

you

will

be

able

to

choose:

?

Which particular device you wish to model, from the list of supported device types (see

Supported Device Types).

?

Whether to add the subsequently-generated SPICE model to an existing component in the

library

document

or

to

a

new

component

that

is

created

by

the

Wizard

and

added

to

that

document.

The SPICE Model Wizard is essentially a collection of wizards - one per device model supported.

This is made especially evident when accessing the Wizard from the Sim Model dialog.

?

If

you wish to add the model to an existing component, and have launched the Wizard

using

the

main

menu

command,

ensure

that

that

component

is

the

active

component

in

the

library.

You

can

also

access

the

Wizard

while

setting

up

a

simulation

model

link

for

an

existing

component.

From

the

Sim

Model

dialog,

simply

ensure

that

the

chosen

entry

in

the

Model

Sub- Kind

field

is

one

of

the

device

types

supported

by

the

Wizard

(see

Supported

Device

Types), then click on the Create button

–

to the right of the Model Name field (Figure 2).

Figure 2. Access the Wizard directly from the Sim Model dialog.

The

Sim

Model

dialog

itself

can

be

accessed

from

a

schematic

library

document

in

one

of

the

following ways:

?

From

the

Library

Component

Properties

dialog

(

Tools

?

Component

Properties

),

by

adding

a

simulation

model

in

the

Models

region

of

the

dialog.

(Applies

to

the

active

component only).

If you are editing an existing linked simulation model, using the Wizard will replace the existing

model with the newly created one.

?

From the SCH Library panel, by adding a simulation model in the Models section of the

panel. (Applies to the active component only).

?

From the Schematic Library Editor's main design window, by adding a simulation model

in the Models region of the window. (Applies to the active component only).

?

From

the

Model

Manager

dialog

(

Tools

?

Model

Manager

),

by

adding

a

simulation

model in the Models region of the dialog. (Applies to the selected component(s)).

Access in the Schematic Editor

Using the Wizard will replace any existing model with the newly created one.

The Wizard can also be accessed when defining the simulation model link for a placed component

on a schematic sheet. Again, access is made from the Sim Model dialog by clicking the Create

button

–

provided of course that the model type is one of those for which a dedicated Wizard is

available.

Figure 3. Accessing the Wizard for a placed schematic component.

Supported Device Types

The Wizard can be used to create SPICE models for the following analog device types:

?

?

?

?

?

?

?

?

Diode

Semiconductor Capacitor

Semiconductor Resistor

Current-Controlled Switch

V

oltage-Controlled Switch

Bipolar Junction Transistor (BJT)

Lossy Transmission Line

Uniform Distributed RC Transmission Line

Naming the Model

When using the Wizard to add a model to a new library component, the name specified for the

model will be used to name the component also.

One of the most important steps as you follow the pages of the Wizard, is to provide a name for

the model

you are creating.

In fact,

you will not be able to proceed to the parameter definition

stage of the Wizard until you have entered a name.

After

creation,

this

name

will

appear

in

the

Model

Name

field

of

the

Sim

Model

dialog.

The

model file itself is also created using this name ().

Figure 4. Define a meaningful name for the model.

When naming the model, you also have the option to enter a short description for it. This could be

the function of the model (e.g. Semiconductor Resistor), or a more specific reference to a value or

configuration (e.g. NPN BJT).

Characteristics to be Modeled

After

giving

the

model

a

name,

you

will

proceed

to

one

or

more

pages

dealing

with

the

characteristics to be modeled. The model types supported by the Wizard can be categorized into

the following two groups:

?

Those models requiring direct entry of values for various model parameters. For further

information, see the section Device Models Created by Direct Parameter Entry.

A parameter specified in the model file for a device will override its default value (inherent to the

SPICE engine).

?

Those models requiring the entry of data from which to extract the parameters that define

the chosen device characteristics. The data entered is obtained either by direct measurement

results from the physical device, or from a manufacturer's data sheet. For further information,

see the section Device Models Created by Parameter Extraction from Data.

Only

parameters

definable

within

a

model

file

are

considered

by

the

Wizard.

Any

parameters that are definable at the component level for a device should be addressed using

the Parameters tab of the Sim Model dialog, once the Wizard has finished creating the model

file.

Generating the Model

After entry of the required data/parameters, the Wizard will display the generated model (Figure

5). This is the content that will be saved to the MDL file.

Figure 5. Previewing the generated model file content.

Editing of the model can be carried out directly on this page, giving you the utmost control over

model specification.

Once

you

are

satisfied

with

the

model

definition,

simply

click

Next

to

pass

to

the

end

of

the

Wizard. Clicking Finish will allow you to save the model. Use the Save SPICE Model File dialog

to determine where the resulting MDL file should be saved. By default, the file will be saved to

the same directory as the schematic library document. You can also change the name of the file at

this stage, should you wish.

If you have requested the model be attached to a new component, that component will be created

and added to the library document.

Although the model is linked automatically to the component

–

new or existing

–

you should make

a habit of verifying the mapping of schematic component pins to pins of the model. Simply access

the

Sim

Model

dialog

for

the

attached

model,

click

on

the

Port

Map

tab,

and

check

the

pin

mapping

–

making any changes if required.

Figure 6. Verify the component-to-model mapping.

Define

any

additional

parameters

available

for

the

model

–

on

the

Parameters

tab

of

the

Sim

Model dialog

–

as required.

Device

Models

Created

by

Direct

Parameter

Entry

For the following device models the Wizard does not extract parameter information from entered

data. Rather, the models are created based on direct entry of values for their associated parameters.

When entering parameter values, there are a couple of things to bear in mind:

?

If a value for a parameter is not specified, there will be no entry for it in the model file

that

is

created.

In

this

case,

the

default

value

stored

internally

in

SPICE

will

be

used.

Put

another way, if a value for a parameter is specified in a model file, then the model file value

overrides that parameter's default value.

?

If the default entry for a parameter in the Wizard is '-' and a value for that parameter is not

specifically entered, a default value of zero will be used (internal to SPICE) for calculations.

Semiconductor Capacitor

The following parameters are definable for this device model, using the Wizard. Entering a value

will cause that parameter to be written to the generated MDL file.

CJ

CJSW

DEFW

Junction bottom capacitance (in F/meters2).

Junction sidewall capacitance (in F/meters).

Default device width (in meters). (Default = 1e-6). This value will be overriden by a

value entered for Width on the Parameters tab of the Sim Model dialog.

NARRO

Narrowing due to side etching (in meters). (Default = 0).

W

For

more

information

on

this

model

type,

refer

to

the

SPICE3f5

modelsGeneralCapacitor

(Semiconductor) section of the

Simulation Models and Analyses Reference

.

Semiconductor Resistor

The following parameters are definable for this device model, using the Wizard. Entering a value

will cause that parameter to be written to the generated MDL file.

TC1

First order temperature coefficient (in Ohms/?C)

. (Default = 0)

TC2

Second order temperature coefficient (in Ohms/?C2). (Default = 0)

RSH

Sheet resistance (in Ohms).

Default width (in meters). (Default = 1e-6). This value will be overriden by a value

DEFW

entered for Width on the Parameters tab of the Sim Model dialog.

NARRO

Narrowing due to side etching (in meters). (Default = 0).

W

Parameter

measurement

temperature

(in

?C).

If

no

value

is

specified,

the

default

TNOM

value assigned to TNOM on the SPICE Options page of the Analyses Setup dialog

will be used (Default = 27).

For

more

information

on

this

model

type,

refer

to

the

SPICE3f5

modelsGeneralResistor

(Semiconductor) section of the

Simulation Models and Analyses Reference

.

Current- Controlled Switch

The following parameters are definable for this device model, using the Wizard. Entering a value

will cause that parameter to be written to the generated MDL file.

IT

Threshold current (in Amps). (Default = 0).

IH

Hysteresis current (in Amps). (Default = 0).

RON

ON resistance (in Ohms). (Default = 1).

OFF resistance (in Ohms). Default = 1/GMIN. GMIN is an advanced SPICE parameter,

ROF

specified on the SPICE Options page of the Analyses Setup dialog. It sets the minimum

F

conductance

(maximum

resistance)

of

any

device

in

the

circuit.

Its

default

value

is

1.0e-12 mhos, giving a default value for ROFF of 1000G Ohms.

For

more

information

on

this

model

type,

refer

to

the

SPICE3f5

modelsSwitchesCurrent

Controlled Switch section of the

Simulation Models and Analyses Reference

.

Voltage- Controlled Switch

The following parameters are definable for this device model, using the Wizard. Entering a value

will cause that parameter to be written to the generated MDL file.

VT

Threshold voltage (in V

olts). (Default = 0).

VH

Hysteresis voltage (in V

olts). (Default = 0).

RON

ON resistance (in Ohms). (Default = 1).

OFF

resistance

(in

Ohms).

By

default

this

is

set

to

1/GMIN.

GMIN

is

an

advanced

SPICE

parameter

setting,

specified

on

the

SPICE Options

page

of

the Analyses

Setup

ROF

dialog.

It

sets

the

minimum

conductance

(maximum

resistance)

of

any

device

in

the

F

circuit.

its

default

value

is

1.0e-12

mhos,

therby

giving

a

default

value

for

ROFF

of

1000G Ohms.

For

more

information

on

this

model

type,

refer

to

the

SPICE3f5

modelsSwitchesV

oltage

Controlled Switch section of the

Simulation Models and Analyses Reference

.

Lossy Transmission Line

The following parameters are definable for this device model, using the Wizard. Entering a value

(or setting a flag) will cause that parameter to be written to the generated MDL file.

R

Resistance per unit length (in Ohms/unit). (Default = 0).

L

Inductance per unit length (in Henrys/unit). (Default = 0).

G

Conductance per unit length (in mhos/unit). (Default = 0).

C

Capacitance per unit length (in Farads/unit). (Default = 0).

LEN

Length of transmission line.

REL

Breakpoint control (in arbitrary units). (Default = 1).

ABS

Breakpoint control (in arbitrary units). (Default = 1).

NOSTEPLIMI

A flag that, when set, will remove the restriction of limiting time- steps to less

T

than the line delay. (Default = not set).

A flag that, when set, prevents limiting of the time-step, based on convolution

NOCONTROL

error criteria. (Default = not set).

A

flag

that,

when

set,

will

use

linear

interpolation

instead

of

the

LININTERP

defaultquadratic

interpolation,

for

calculation

of

delayed

signals.

(Default

=

not set).

A

flag

that,

when

set,

uses

a

metric

for

determining

whether

quadratic

MIXEDINTER

interpolation is applicable and, if it isn't, uses linear interpolation. (Default =

P

not set).

A specific quantity used to control the compaction of past history values used

COMPACTRE

for

convolution.

By

default,

this

quantity

uses

the

value

specified

for

the

L

relative simulation error tolerance parameter (RELTOL), which is defined on

the SPICE Options page of the Analyses Setup dialog.

A specific quantity used to control the compaction of past history values used

COMPACTAB

for

convolution.

By

default,

this

quantity

uses

the

value

specified

for

the

S

absolute current error tolerance parameter (ABSTOL), which is defined on the

SPICE Options page of the Analyses Setup dialog.

A flag that, when set, turns on the use of the Newton-Raphson iteration method

to

determine

an

appropriate

time-step

in

the

time-step

control

routines.

TRUNCNR

(Default

=

not

set,

whereby

a

trial

and

error

method

is

used

–

cutting

the

previous time-step in half each time).

TRUNCDONT

CUT

A

flag

that,

when

set,

removes

the

default

cutting

of

the

time-step

to

limit

errors in the actual calculation of impulse-response related quantities. (Default

= not set).

For the resultant model to simulate, at least two of the R, L, G, C parameters must be given a

value and also a value must be entered for the LEN parameter. You will not be able to proceed

further in the Wizard until these conditions are met.

For more information on this model type, refer to the SPICE3f5 modelsTransmission LinesLossy

Transmission Line section of the

Simulation Models and Analyses Reference

.

Uniform Distributed RC Transmission Line

The following parameters are definable for this device model, using the Wizard. Entering a value

will cause that parameter to be written to the generated MDL file.

K

Propagation constant. (Default = 2).

FMAX

Maximum frequency of interest (in Hertz). (Default = 1.0G).

RPERL

Redsistance per unit length (in Ohms/meter). (Default = 1000).

CPERL

Capacitance per unit length (in Farads/meter). (Default = 1.0e-15).

ISPERL

Saturation current per unit length (in Amps/meter). (Default = 0).

RSPERL

Diode resistance per unit length (in Ohms/meter). (Default = 0).

For

more

information

on

this

model

type,

refer

to

the

SPICE3f5

modelsTransmission

LinesUniform

Distributed

RC

(lossy)

Transmission

Line

section

of

the

Simulation

Models

and

Analyses Reference

.

Device

Models

Created

by

Parameter

Extraction from Data

For Diode and BJT devices, the Wizard extracts parameter information from data you enter. The

specific

parameters

extracted

for

inclusion

in

the

model

file

will

depend

on

the

particular

characteristics of the diode or BJT you have chosen to model.

The method of data entry varies between characteristics. In some cases, you will be required to

enter direct data values, in others the entry of plot data. In any case all data will be sourced from

direct device measurements, a manufacturer's data sheet, or a combination of the two.

For plot-based data, entering more data points will provide the Wizard with a truer 'picture' of the

source data, which in turn leads to the greater accuracy of extracted parameter values.

When you are required to enter plot data, simply enter a series of data points obtained from the

graphical source data, into the grid provided by the Wizard (Figure 7). If you have the data stored

in comma separated value (*.csv) format, you can import the data using the available Import Data

button. The Wizard will take the data you enter and use it to extract the required model parameters.

The results of the extraction are presented on a subsequent page of the Wizard

–

in terms of the

extracted

parameter

values

themselves,

and

a

comparison

plot

of

the

data

entered

and

values

calculated

using

the

extracted

parameters.

Figure

7

illustrates

an

example

of

such

a

display

of

parameter results.

Figure 7. Enter source data for the Wizard to be able to extract the required model parameters.

You can edit the extracted parameter values to further refine the accuracy of the diode model. The

graphical comparison will be updated to reflect the changes.

Diode

The following sections detail each of the characteristics that you can choose to model for a diode

device.

Each

section

discusses

the

parameters

extracted

and

the

source

data

required

by

the

Wizard to facilitate their extraction.

For more information on this model type, refer to the SPICE3f5 modelsGeneralDiode section of

the

Simulation Models and Analyses Reference

.

Forward-bias current flow

The following parameters are used to describe the DC current-voltage characteristics of the diode

in the forward-bias region:

IS

Saturation current ( in Amps).

N

Emission coefficient.

RS

Ohmic resistance (in Ohms).

To extract these parameters, a graph of the forward diode current (IF)

versus the forward diode

voltage (VF) is required. This graph can be obtained either from a manufacturer's data sheet or by

measurements performed on a physical device.

Figure 8 shows an example of such a graph, obtained from a data sheet, and also an example test

circuit, from which direct measurements could be taken to obtain the required source data.

Figure 8. Example graph and circuit for diode I-V characteristics in the forward-bias region.

Data is entered into the Wizard as a series of data points obtained from the source graph.

Reverse-bias junction capacitance

The following parameters are used to describe the capacitance of the diode when operating in the

reverse-bias region:

CJO

Zero-bias junction capacitance (in Farads).

M

Grading coefficient.

VJ

Junction potential (in V

olts).

To

extract

these

parameters,

a

graph

of

the

reverse-biased

capacitance

(Cd)

versus

the

reverse

diode voltage (VR) is required. This graph can be obtained either from a manufacturer's data sheet

or by measurements performed on a physical device.

Figure 9 shows an example of such a graph, obtained from a data sheet, and also an example test

circuit, from which direct

measurements could be taken to obtain the required source data. The

latter can be used if a capacitance meter is not available.

Figure 9. Example graph and circuit for diode capacitance in the reverse-bias region.

Data is entered into the Wizard as a series of data points obtained from the source graph.