PSpice User's Guide
Contents
1. VSRC VEXP VPULSE VPWL VPWL_RE_FOREVER VPWL_F_RE_FOREVER VPWL_N_TIMES VPWL_F_N_TIMES VSFFM VSIN voltage sources Table 32 Stimulus symbols for time based input signals Specified by Symbol name Description ISRC current sources TEXP IPULSE IPWL IPWL_RE_FOREVER IPWL_F_RE_ FOREVER IPWL_N_TIMES IPWL_F_N_TIMES ISFFM ISIN DIGCLOCK digital clock signal STIM1 digital stimuli STIM4 STIM8 STIM16 FILESTIM1 digital file stimuli FILESTIM2 FILESTIM4 FILESTIM8 FILESTIM16 FILESTIM32 To use any of these source types you must place the symbol in your schematic and then define its transient behavior Each property characterized stimulus has a distinct set of attributes depending upon the kind of transient behavior it represents For VPWL_F_xxx IPWL_F_xxx and FSTIM a separate file contains the stimulus specification As an alternative the Stimulus Editor utility automates the process of defining the transient behavior of stimulus devices The Stimulus Editor allows you to create analog stimuli which generate sine wave repeating pulse exponential pulse single frequency FM and piecewise linear waveforms It also facilitates creating digital stimuli with complex timing relations This applies to both stimulus symbols placed in your schematic as well as new ones that you might create Defining a time based stimulus Not in PSpice Note Digital stimuli are not supported in PSpice For i2. The values at the print time steps are obtained by second order polynomial interpolation from values at the internal steps When simulating mixed analog digital circuits there are actually two time steps one analog and one digital This is necessary for efficiency Since the analog and digital circuitry usually have very different time constants any attempt to lock them together would greatly slow down the simulation The time step shown on the PSpice display during a transient analysis is that of the analog section Switching circuits in transient analyses Switching circuits in transient analyses Running transient analysis on switching circuits can lead to long run times PSpice must keep the internal time step short compared to the switching period but the circuit s response extends over many switching cycles One method of avoiding this problem is to transform the This technique is described in switching circuit into an equivalent circuit without V Bello Computer Program Adds SPICE to switching The equivalent circuit represents a sort of quasi Switching R egulator Analysis Electronic steady state of the actual circuit and can correctly model Design March 5 1981 i the actual circuit s response as long as the inputs do not change too fast Plotting hysteresis curves Transient analysis can be used to look at a circuit s hysteresis Consider for instance the circuit shown in Figure 66 netlist in Figur
3. analysis causes the response of the circuit to be calculated from TIME 0 to a specified time A transient analysis specification is shown for the circuit EXAMPLE OPJ in Figure 64 EXAMPLE OP is shown in Figure 65 The analysis is to span the time interval from 0 to 1000 nanoseconds and values should be reported to the simulation output file every 20 nanoseconds 373 Chapter 11 Transient analysis General Settings OM Carlo Worst Case OParametric Sweep Temperature Sweep OSave Bias Point Load Bias Point Figure 64 Transient analysis setup for EXAMPLE OPJ During a transient analysis any or all of the independent sources may have time varying values In EXAMPLE OPJ the only source which has a time varying value is V1 VSIN part with attributes VOFF Ov VAMPL 0 1v FREQ 5Meg V1 s value varies as a 5 MHz sine wave with an offset voltage of 0 volts and a peak amplitude of 0 1 volts In general more than one source has time varying values for instance two or more clocks in a digital circuit 374 VOU readme RAIAS RCI RC2 example rdm 2k n CLOAD En OUTI d 4 OUT2 ast BA YN o AS wi y k q212222 q212222 tk qd at at es eee 4212222 4d Ha q212222 E roo ro VEE Figure 65 Example schematic EXAMPLE OPJ The transient analysis does its own calculation of a bias point to start with using th
4. in a detailed description of their syntax see the descriptions of V and I devices in the Analog Devices chapter and stimulus generator in the Digital Devices chapter of the the online PSpice Reference Guide Configuring stimulus files The Include Files tab in the Simulation Settings dialog box allows you to view the list of stimulus files pertaining to your current schematic You can also manually add delete or change the stimulus file configuration in this tab dialog box The list box displays all of the currently configured stimulus files One file is specified per line Files can be configured as either global to the Capture environment or local to the current design Global files are marked with an asterisk after the file name When starting the Stimulus Editor from Capture stimulus files are automatically configured added to the list as local to the current design Otherwise new stimulus files can be added to the list by entering the file name in the Filename text box and then clicking the Add to design local configuration or Add as global global configuration button Starting the Stimulus Editor The Stimulus Editor is fully integrated with Capture and can be run from either the schematic editor or symbol editor You can start the Stimulus Editor by doing the following 1 Select one or more stimulus instances in the schematic 2 From the Edit menu choose PSpice Stimulus When you first start the Stimulus Editor y
5. ANALOG or DIGITAL if this property is nonexistent the stimulus is assumed to be ANALOG 369 Chapter 11 Transient analysis PWL stimuli are a little different since they are a series of time value pairs This provides a fast way to scale a PWL stimulus 370 Editing a stimulus To edit an existing stimulus 1 Start the Stimulus Editor and select Get from the Stimulus menu 2 Double click the trace name at the bottom of the X axis for analog and to the left of the Y axis for digital traces This opens the Stimulus Attributes dialog box where you can modify the attributes of the stimulus directly and immediately see the effect of the changes To edit a PWL stimulus Double click the trace name This displays the handles for each defined data point 2 Click any handle to select it To reshape the trace drag it to a new location To delete the data point press Del 3 To add additional data points either select Add from the Edit menu or click the Add Point button 4 Right click to end adding new points To select a time and value scale factor for PWL stimuli l Select the PWL trace by clicking on its name 2 Select Attributes from the Edit menu or click the corresponding toolbar button The Stimulus Editor utility Deleting and removing traces To delete a trace from the displayed screen select the trace name by clicking on its name then press Del This will only erase the display of the trace not
6. Transient analysis Chapter overview This chapter describes how to set up a transient analysis and includes the following sections Overview of transient analysis on page 11 360 Defining a time based stimulus on page 11 362 Transient time response on page 11 373 Internal time steps in transient analyses on page 11 376 Switching circuits in transient analyses on page 11 377 Plotting hysteresis curves on page 11 377 Fourier components on page 11 379 Chapter 11 Transient analysis Overview of transient analysis Minimum requirements to run a transient analysis Minimum circuit design requirements Circuit should contain one of the following e Anindependent source with a transient specification see Table 32 e An initial condition on a reactive element e A controlled source that is a function of time Minimum program setup requirements General Analysis Include Files Libraries Stimulus Options Data Collection Probe Window Analysis type Run to time fi O00ns seconds TSTOP Print values in the output file every fi Ons seconds Transient options Maximum step size seconds I Skip the initial transient bias point calculation SKIPBP Time Domain Transient General Settings Monte CarloAWorst Case Parametric Sweep Temperature Sweep Save Bias Point Load Bias Point Output File Options Cancel pal Help See Setting up
7. analyses on From the PSpice menu choose New Simulation page 8 284 for a description of the Profile or Edit Simulation Settings If this is a new Analysis Setup dialog box simulation enter the name of the profile and click OK 360 Overview of transient analysis The Simulation Settings dialog box appears From the Analysis type list box select Time Domain Transient Specify the required parameters for the transient analysis you want to run Click OK to save the simulation profile From the PSpice menu choose Run to start the simulation 361 Chapter 11 Transient analysis Not in Basics Note Stimulus Editor is not included with PSpice A D Basics Not in PSpice Note Digital stimuli are not supported in PSpice 362 Defining a time based stimulus Overview of stimulus generation Symbols that generate input signals for your circuit can be divided into two categories e those whose transient behavior is characterized graphically using the Stimulus Editor e those whose transient behavior is characterized by manually defining their properties within Capture Their symbols are summarized in Table 32 Table 32 Stimulus symbols for time based input signals Specified by Symbol name Description Using the Stimulus Editor VSTIM ISTIM DIGSTIM1 DIGSTIM2 DIGSTIM4 DIGSTIM8 DIGSTIM16 DIGSTIM32 voltage source current source digital stimuli Defining symbol attribute
8. analysis is to be used and the fundamental frequency is to be one megahertz for the harmonic decomposition The period of fundamental frequency is one microsecond inverse of the fundamental frequency Only the last one microsecond of the transient analysis is used and that 379 Chapter 11 Transient analysis 380 portion is assumed to repeat indefinitely Since V1 s sine wave does indeed repeat every one microsecond this is sufficient In general however you must make sure that the fundamental Fourier period fits the waveform in the transient analysis Parametric and temperature analysis 12 Chapter overview This chapter describes how to set up parametric and temperature analyses Parametric and temperature are both simple multi run analysis types This chapter includes the following sections e Parametric analysis on page 12 382 e Temperature analysis on page 12 391
9. delete it from your file The trace is still available by selecting Get from the Stimulus menu To remove a trace from a file select Remove from the Stimulus menu Note Once a trace is removed it is no longer retrievable Delete traces with caution Manual stimulus configuration Stimuli can be characterized by manually starting the Stimulus Editor and saving their specifications to a file These stimulus specifications can then be associated to stimulus instances in your schematic or to stimulus symbols in the symbol library To manually configure a stimulus l Start the Stimulus Editor by double clicking on the Stimulus Editor icon in the Orcad program group 2 Open a stimulus file by selecting Open from the File menu If the file is not found in your current library search path you are prompted for a new file name 3 Create one or more stimuli to be used in your schematic For each stimulus a Name it whatever you want This name will be used to associate the stimulus specification to the stimulus instance in your schematic or to the symbol in the symbol library b Provide the transient specification From the File menu choose Save 371 Chapter 11 Transient analysis 372 In the schematic page editor configure the Stimulus Editor s output file into your schematic a From the Pspice menu choose Edit Simulation Profile a Inthe Simulation Settings dialog box select the Include Files tab b Enter t
10. e 67 3 g4 a az 2 7 HE Z QSTD n i ASTD a f Z asto Ps Rin 50 4 1 Rl 3 RATHI ww AM Aiit i 185 760 125 e RCI 50 cLoap VEE pee PThE aan in a Figure 66 ECL compatible Schmitt trigger 377 Chapter 11 Transient analysis 378 Capture Netlist R_RIN 1 2 50 R_RC1 0 3 50 R_R 3 5 185 R_R2 5 8 760 R_RC2 0 6 100 R_RE 4 8 260 R_RTH2 7 0 85 C_CLOAD 0 7 SPF V_VEE 8 0 dc 5 V_VIN 10 PWL O 8 IMS 1 0V 2MS 1 8V R_RTH1 8 7 125 QQ 3 2 4 QSTD Q_Q2 6 5 4 QSTD Q_Q3 0 6 7 QSTD Q_04 0 6 7 QSTD Figure 67 Netlist for Schmitt trigger circuit The QSTD model is defined as MODEL OSTD NPN is 1e 16 bf 50 br 0 1 rb 50 rc 10 tf 12ns tr 5ns cje 4pF pe 8 me 4 gc 5pF pc 8 mc 333 ccs 1pF va 50 Instead of using the DC sweep to look at the hysteresis use the transient analysis Print Step 01ms and Final Time 2ms sweeping VIN from 1 8 volts to 1 0 volts and back down to 1 8 volts very slowly This has two advantages e it avoids convergence problems e it covers both the upward and downward transitions in one analysis After the simulation in the Probe window in PSpice the X axis variable is initially set to be Time By selecting X Axis Settings from the Plot menu and clicking on the Axis Variable button you can set the X axis variable to be V 1 Then use Add on the Trace menu to display V 7 and change the X ax
11. e same technique as described for DC sweep This is necessary because the initial values of the sources can be different from their DC values To report the small signal parameters for the transient bias point use the Transient command and enable Detailed Bias Point Otherwise if you simply want the result of the transient run itself you should only enable the Transient command In the simulation output file EXAMPLE OUT the bias point report for the transient bias point is labeled INITIAL TRANSIENT SOLUTION Transient time response The example circuit EXAMPLE OPJ is provided with the Orcad program installation 375 Chapter 11 Transient analysis See Chapter 14 Digital simulation for more information on the digital timing analysis of PSpice A D 376 Internal time steps in transient analyses During analog analysis PSpice maintains an internal time step which is continuously adjusted to maintain accuracy while not performing unnecessary steps During periods of inactivity the internal time step is increased During active regions it is decreased The maximum internal step size can be controlled by specifying it in the Maximum Time Step text box in the Transient dialog box PSpice will never exceed either the step ceiling value or two percent of the total transient run time whichever is less The internal time steps used may not correspond to the time steps at which information has been requested to be reported
12. he Stimulus Editor Fill in the transient specification according to the dialogs and prompts Piecewise linear and digital stimuli can be specified by direct manipulation of the input waveform display From the File menu choose Save to save the edits Example piecewise linear stimulus l 2 Open an existing schematic or start a new one From the Place menu choose Part and browse the SOURCESTM OLB part library file for VSTIM and select it Place the part It looks like a regular voltage source with an implementation property displayed Click the implementation label and type vfirst This names the stimulus that you are going to create If you are working in a new schematic use Save from the File menu to save it This is necessary since the schematic name is used to create the default stimulus file name Click the VSTIM part to select it From the Edit menu choose PSpice Stimulus This starts the Stimulus Editor and displays the New The Stimulus Editor utility Stimulus dialog box You can see that the stimulus already has the name of Vfirst 8 Select PWL in the dialog box and click OK The cursor looks like a pencil The message in the status bar at the bottom of the screen lets you know that you are in the process of adding new data points to the stimulus The left end of the bottom status bar displays the current coordinates of the cursor 9 Move the cursor to 200ns 1 and click the left mouse button Th
13. he file name specified in step 2 c Ifthe stimulus specifications are for local use in the current design click the Add to design button For global use by any design use Add as global instead d Click OK Modify either the stimulus instances in the schematic or symbols in the symbol library to reference the new stimulus specification Associate the transient stimulus specification to a stimulus instance a Place a stimulus part in your schematic from the part set VSTIM ISTIM and DIGSTIMn b Click the VSTIM ISTIM or DIGSTIMn instance From the Edit menu choose Properties d Click the Implementation cell type in the name of the stimulus and click Apply e Complete specification of any VSTIM or ISTIM instances by selecting Properties from the Edit menu and editing their DC and AC attributes Click the DC cell and type its value Click the AC cell type its value and then click Apply f Close the property editor spreadsheet 7 Transient time response To change stimulus references globally for a part a a Select the part you want to edit From the Edit menu choose Part to start the part editor Create or change the part definition making sure See Chapter 5 Creating parts for to define the following properties models for a description of how to create and edit parts Implementation stimulus name as defined in the Stimulus Editor Transient time response The Transient response
14. is adds the point Notice that there is automatically a point at 0 0 Ignore it for now and continue to add a couple more points to the right of the current one 10 Click right to stop adding points 11 From the File menu choose Save If you make a mistake or want to make any changes reshape the trace by dragging any of the handles to a new location The dragged handle cannot pass any other defined data point To delete a point click its handle and press Del To add additional points either choose Add Point from the Edit menu press Alt HA or click the Add Point toolbar button At this point you can return to Capture edit the current stimulus or go on to create another Example sine wave sweep This example creates a 10 k sine wave with Open an existing schematic or start a new one Aan be swept during a simulation 2 Place a VSTIM part on your schematic 3 To name the stimulus double click the implementation property and type Vsin 4 Click the VSTIM part to select it 5 From the PSpice menu choose Edit Stimulus to start the Stimulus Editor the amplitude parameterized so that it can Chapter 11 Transient analysis 368 Define the stimulus parameter for amplitude From the New Stimulus dialog box choose Cancel From the Tools menu choose Parameters Enter AMP 1 in the Definition text box and click OK From the Stimulus menu choose New or click the New Stimulus button in the toolbar Gi
15. is to a user defined data range from 1 8V to 1 0V Axis Settings on the Plot menu This plots the output of the Schmitt trigger against its input which is the desired outcome The result looks similar to Figure 68 Fourier components GS PR aaa aaa oar Ta i j Li f ji I I I I 4 204 I I I I I I I I ii I 4 6U 4 I I eek I 1 2 89 22 22 22 22 22 22 jeocnce ee ecnen nen l 1 1 6U 14 40 1 20 1 0U UC u 1 Figure 68 Hysteresis curve example Schmitt trigger Fourier components Fourier analysis is enabled through the Output File Options dialog box under the Time Domain Transient Analysis type Fourier analysis calculates the DC and Fourier components of the result of a transient analysis By default the first through ninth components are computed however more can be specified Note You must do a transient analysis in order to do a Fourier analysis The sampling interval used during the Fourier transform is equal to the print step specified for the transient analysis When selecting Fourier to run a harmonic decomposition analysis on a transient waveform only a portion of the waveform is used Using the Probe window in PSpice a Fast Fourier Transform FFT of the complete waveform can be calculated and its spectrum displayed In the example shown in Figure 64 on page 11 374 the voltage waveform at node OUT2 from the transient
16. nformation on digital stimuli characterized by property see Chapter 14 Digital simulation 363 Chapter 11 Transient analysis Not in Basics Orcad program versions without the Stimulus Editor must use the characterized by property sources listed in Table 32 on page 11 362 364 The stimulus specification created using the Stimulus Editor is saved to a file automatically configured into the schematic and associated with the corresponding VSTIM ISTIM or DIGSTIM part instance or symbol definition The Stimulus Editor utility The Stimulus Editor is a utility that allows you to quickly set up and verify the input waveforms for a transient analysis You can create and edit voltage sources current sources and digital stimuli for your circuit Menu prompts guide you to provide the necessary parameters such as the rise time fall time and period of an analog repeating pulse or the complex timing relations with repeating segments of a digital stimulus Graphical feedback allows you to quickly verify the waveform Stimulus files The Stimulus Editor produces a file containing the stimuli with their transient specification These stimuli are defined as simulator device declarations using the V voltage source I current source and U STIM digital stimulus generator forms Since the Stimulus Editor produces these statements automatically you will never have to be concerned with their syntax However if you are interested
17. ou may need to adjust the scale settings to fit the trace you are going to add You can use Axis Settings on the Plot menu or the corresponding toolbar button to change the displayed data the extent of the scrolling region and the minimum resolution for each of the axes Displayed Data Range parameters determine what portion of the stimulus data set will be presented on the screen Extent of Scrolling Region parameters set the absolute limits on the viewable range Minimum Resolution parameters determine the imulation Settings Transient Analysis General Analysis Include Files Libraries Stimulus Options Data Collection Probe Window Fllename The Stimulus Editor utility Include Files Browse Add as Global Add to Design Remove Include files are loaded before the circuit They can include most valid PSpice commands such as PARAM le and FUNC definitions Cancel Apply Help 365 Chapter 11 Transient analysis See Chapter 14 Digital simulation for detailed information about creating digital stimuli 366 smallest usable increment example if it is set to 1 msec then you cannot add a data point at 1 5 msec Defining stimuli l Place stimulus part instances from the symbol set VSTIM ISTIM and DIGSTIMn found in the SOURCESTM OLB part library Click the source instance to select it From the Edit menu choose PSpice Stimulus to start t
18. ve the stimulus the name of Vsin Select SIN as the type of stimulus to be created and click OK Define the other stimulus properties Enter o for Offset Value Enter AMP for Amplitude The curly braces are required They indicate that the expression needs to be evaluated at simulation time Enter 10k for Frequency and click OK From the File menu choose Save Within Capture place and define the PARAM symbol f From the Place menu choose Part Either browse SPECIAL OLB for the PARAM part or type in the name Place the part on your schematic and double click it Click New to add a new user property Set the value property name to AMP no curly braces Set the value of the AMP property to 1 Set up the parametric sweep and other analyses a b From the PSpice menu choose Edit Simulation Profile and click the Parametric Sweep button Select Global Parameter in the Swept Var Type frame The Stimulus Editor utility c Select Linear in the Sweep type frame 10 Enter amp in the Name text box 11 Specify values for the Start Value End Value and Increment text boxes You can now set up your usual Transient AC or DC analysis and run the simulation Creating new stimulus symbols 1 Use the Capture part editor to edit or create a part with the following properties Implementation Type PSpice Stimulus Implementation name of the stimulus model STIMTYPE type of stimulus valid values are
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