DVM - Design Verification Module
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DVM - Design Verification Module
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The ArbitraryBodePlot() function allows you to create a Bode plot with gain and/or phase curves from reference designators or from a pair of net names on a specified graph address.
The ArbitraryBodePlot() function can create the following types of curves:
Although the Bode Plot Probe - w/ Measurements schematic symbol has similar functionality, the ArbitraryBodePlot() testplan function includes formatting options that increase the flexibility of this function. One such option makes it possible to probe between schematic hierarchical levels.
For example, plotting the gain and phase of the compensation error amplifier in the LTC3406B circuit is difficult with the schematic-based probe because the output of the error amplifier is not at the top level of the hierarchy. Bringing the output of that error amplifier to the top level would require a modification to the LTC3406B symbol. Using the ArbitraryBodePlot() function, however, solves this problem because with this function, you can directly probe the nets in the schematic hierarchy and generate the curves without making any changes to the schematic.
In this Topic Hide
The ArbitraryBodePlot() function has four forms as listed below.
| Argument Name | Description |
| REFIN | Reference designator for positive and negative input net (See note at bottom of table.) |
| REFOUT | Reference designator for positive and negative output net (See note at bottom of table.) |
| netIN+ | Positive input net name |
| netIN- | Negative input net name |
| netOUT+ | Positive output net name |
| netOUT- | Negative output node |
| curve_name | Name for the curve |
| graph_name | Name for the graph as seen on test report* |
| grid_index | Grid on which to place the curve* |
| axis_name | Name for the axis on a particular grid* |
OPTIONAL_PARAMETER_STRING |
Optional curve formatting parameters** |
Note: If you use reference designators as the arguments to this function, the symbol must have two terminals or be a DVM load symbol. The program resolves the net names from the symbol and then plots the differential voltage across the power pins on the symbol.
* For additional information about graph_name, grid_index, and axis_name, see Graph Address System.
** For additional information about OPTIONAL_PARAMETER_STRING, see Optional Parameters.
This example generates a closed loop gain of an op-amp using the last function form listed above.
ArbitraryBodePlot(netIN+, netIN-, netOUT+, netOUT-, curve_name, graph_name, grid_index, axis_name, OPTIONAL_PARAMETER_STRING)
The specific function call is as follows:
ArbitraryBodePlot(input, 0, out, 0, DVM Closed Loop,
Closed Loop, A1, ignoreme, curve=splitphase color=Medium violet red)
This example plots the gain, db(out/input), and the phase, ph(out/input), on two grids with the phase on the upper grid.
Both the gain and phase curves are set to the same color based on the value of color in the optional parameter string.
Because the optional parameter string contains the curve=splitphase option, the grid_index and axis_name arguments are ignored.
The phase curve is placed on upper grid which is grid_index=A2 and the gain curve on the lower which is grid_index=A1.
The default names of the two axes are bodephase and bodemag, and the fixed Bode plot probe uses these axis names, allowing the ArbitraryBodePlot() curves to be placed on the same axis as the fixed probe.
The y-axis labels are also renamed Phase and Gain, since the default label is the same as curve_name.
Since on a split grid, the curve names are almost always too long to fit, the curve names are concatenated from the curve_name argument with the following logic:
If the curve_name argument contains the substirng Gain or gain, the program assumes that is the gain curve name and then replaces Gain with Phase to generate the phase curve name.
If the curve name argument contains the substring Phase or phase, the program assumes that is the phase curve name and then replaces Phase with Gain to generate the gain curve name.
Finally, if the specified curve name contains neither gain or phase, the program adds "Gain" and " Phase" with the leading space to the end of the specified name.
As a result, all of the following specified curve names produce the same names for the gain and phase curves.
| Specified Curve Name | Resulting Gain Curve Name | Resulting Phase Curve Name |
| DVM Loop Gain | DVM Loop Gain (as specified) | DVM Loop Phase (replaces Gain with Phase) |
| DVM Loop Phase | DVM Loop Gain (replaces Phase with Gain) | DVM Loop Phase (as specified) |
| DVM Loop | DVM Loop Gain (adds Gain to specified name) | DVM Loop Phase (adds Phase to specified name) |
Explicit curve names can be assigned by making two calls to the ArbitraryBodePlot() function - one with curve=gain and another with curve=phase. When a single curve is generated by the ArbitraryBodePlot() function, all arguments to the ArbitraryBodePlot() curve function are taken literally, with no substitutions.
The following syntax rules apply to the OPTIONAL_PARAMETER_STRING argument:
ylabel=Body Diode Forward
Current
Temp=-40
Spaces in values are allowed as long as no spaces are on either side
of the equal sign. Thee three examples below illustrate this:
The following table lists the available formatting options for use in the OPTIONAL_PARAMETER_STRING argument.
| Parameter Syntax | Value Type | Description |
| xgrid= positive_integer |
Any positive integer | Specifies space between the x gridlines |
| ygrid= positive_integer |
Any positive integer | Specifies space between the y gridlines |
| xscale=lin | log | One of two options:
|
Specifies the units for the x axis |
| yscale=lin | log | One of two options:
|
Specifies the units for the y axis |
| xlabel=string | Any alphanumeric string | Specifies a label for the x axis |
| ylabel=string | Any alphanumeric string | Specifies a label for the y axis
Note:
The |
| xunits=string | Any alphanumeric string | Specifies the units label for the x axis |
| yunits=string | Any alphanumeric string | Specifies the units label for the y axis.
Note:
The ArbitraryBodePlot() |
| xMinlimit=integer | Any positive or negative integer | Specifics the minimum x-axis limit |
| xMaxlimit=integer | Any positive or negative integer | Specifics the maximum x-axis limit |
| yMinlimit=integer | Any positive or negative integer | Specifics the minimum y-axis limit |
| yMaxlimit=integer | Any positive or negative integer | Specifics the maximum y-axis limit |
| showpoints= TRUE | FALSE |
TRUE or FALSE | Specifies whether or not to show points on graph. |
| curve= gain|phase |
One of following options:
|
Generates a curve based on the graph address parameters: graph_name, grid_index, and axis_name. |
curve= |
One of the following options:
|
Generates both a gain curve and a phase curve based on the graph_name parameter only. Both grid_index and axis_name are ignored since the parameter itself determines the grid that is used. |
format=center |
String value: center | Centers both the gain 0-dB and 0-degree grid lines on the gain and phase grids so that they are aligned. The maximum or minimum y axis values are not scaled, and the grid spacing is automatically selected by SIMetrix. |
format=center_m_n |
Alphanumberic string that starts with center | Centers the grid lines as with format=center, but also sets the gain grid to m dB and the phase grid to n degrees. For example format=center_20_45 sets the gain axis major grid to 20dB and the phase axis major grid to 45 degrees. |
format=alignzero |
String value: alignzero | Aligns the gain 0-dB grid line with the phase 0-degree grid line and changes the gain grid to 20dB/division and the phase axis grid to 45 degrees. |
format=alignzero_m_n |
Alphanumberic string that starts with alignzero | Aligns the grid lines as with format=alignzero, but also sets the gain grid to m dB and phase grid to n degrees. For example format=alignzero_40_90 sets the gain axis major grid to 40dB and the phase axis major grid to 90 degrees. |
| color= color_specification |
One of three options to specify the color:
|
Specifies the color for the curve.
Note: See the next section for information on these three methods for specifying a color.. |
You have three options for specifying the color for a curve:
The syntax for the color-name alias is as follows:
color=color_name
where color_name is one of the
16 built-in color aliases as listed in the following table with the hexadecimal
code.
| Color Name Alias | Hex Code | |
| Red | #FF0000 | |
| Green | #008000 | |
| Blue | #0000FF | |
| Teal | #008080 | |
| Purple | #800080 | |
| Maroon | #800000 | |
| Navy | #000080 | |
| Black | #000000 | |
| Magenta | #FF00FF | |
| Lime | #00FF00 | |
| Salmon | #FA8072 | |
| Medium violet red | #C71585 | |
| Brown | #A52A2A | |
| Indigo | #4B0082 | |
| Medium orchid | #BA55D3 | |
| Blue violet | #8A2BE2 | |
The syntax for the hexidecimal color is as follows:
color=#rrggbb
where rr, gg,
and bb are hex numbers from 00
to FF.
You can specify any color for the curve by using a hexadecimal specification.
The syntax for the SIMetrix sequence method of specifying a color is
as follows:
color=SEQ:n
where n is a positive integer between
1 and 20.
SIMetrix has eight default curve colors, starting with red, green, blue, etc.
To change and extend these colors to a maximum of 20 user-defined curve colors, follow these steps:
Note: If you do not set each Curve item in the list, the sequence wraps; for example, with the default curve colors, SEQ:9 yields the same curve color as SEQ:1.
The ArbitraryBodePlot() function is also available as a SIMetrix script function and can be called from a PostProcess or FinalProcess script. Calling this function from a script is useful when you need to generate a large number of curves and/or if the length of the arguments makes the testplan difficult to read or edit.
The syntax for the function in a script is as follows:
SimplisDVMAdvancedUtilMeasurementArbitraryBodePlot(array,
log_file)
| Argument | Description |
array |
A string array that contains the normal arguments to the CreateArbitraryBodePlot() function |
log_file |
The DVM log file that is an argument passed into the post and final process scripts |
The Example above could be generated in a post-process script with the following statement:
| Let return = SimplisDVMAdvancedUtilMeasurementArbitraryBodePlot([ 'input', '0', 'out', '0', 'DVM Closed Loop', 'Closed Loop', 'A1', 'ignoreme', 'curve=splitphase color=Medium violet red' ], log_file) |
Note: The array argument is bounded by open and close brackets [ ], and the string elements in the array are each enclosed in single quotes.
Note: Using the script function in a post or final process script produces slightly different results than calling this function from a testplan. The post-process script does not set the vectors_to_keep argument because this would need to be performed before the simulation run executes. The simplest way to keep the necessary vectors during a simulation run is to place a voltage probe on the required schematic node and uncheck each Analysis checkbox in the edit dialog. This probe would then keep the voltage or current to which it is attached but would not create a curve.
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