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How to Leverage PSpice For Pre-Layout Simulation FAQs

PSpice | Simulation and Settings | PSpice Models | Other

PSpice

1. Does PSpice support any ISO sources to test circuits used in automotive applications?

Yes, with PSpice, ISO transient sources for standard 7637-2 and 16750-2 are shipped, which generate transient pulses as per standard. One can include them in their circuit to simulate the response of a circuit for such a transient pulse. In addition, we also ship exponential sources where one can model pulses as per their specific requirement for voltage and current level, pulse repetition interval, and number of burst pulses.

2. Can we use Cadence PSpice to simulate an RF circuit?

Yes, Cadence offers simulation for RF analysis. PSpice can be used for functional simulation of RF circuits using the SPICE simulator; however, PSpice does not offer RF circuit simulation-related objects such as s-parameters, Smith charts, etc. Look at the Cadence AWR design platform—specifically, Microwave Office—for more information on RF solutions.

3. Can we do microcontroller simulation in PSpice?

Yes. One can use C/C++ to define model logic and simulate along with the rest of the circuit with SPICE models. PSpice is the only simulator with a built-in digital simulator kernel; it seamlessly simulates Analog and Digital circuits together.

4. Can PSpice simulate total PCB power consumption in pre-layout?

Yes, PSpice can calculate PCB pre-layout power consumption. With PSpice simulation, the power consumption of components is always computed, and one can easily derive total power consumption, power delivery, power loss in individual devices, and overall efficiency.

5. Do I need a GPU to use parallel PSpice simulation?

No, it leverages CPU cores.

6. How is PSpice helpful in developing the PCB? Can we get any help in designing the PCB with the help of Schematic in PSpice?

PSpice assists in PCB development by enabling pre-layout simulation of circuit behavior, ensuring functional correctness, stability, and performance before physical design begins. It assists with component selection, signal integrity, power dissipation, and tolerance analysis, allowing designers to validate and optimize analog mixed signal circuits. While it doesn't create the PCB layout, it has an indirect impact by ensuring the schematic is robust, reducing costly design iterations later.

7. Is Cadence PSpice an add-on (with a license fee) feature? How's the model library?

A base version of PSpice is included with all tiers of OrCAD X and Allegro X and includes a default PSpice library of over 38,000 models.

8. How can PSpice be used to detect over-voltage conditions and part reliability?

PSpice comes with an Advanced Analysis Tool for SMOKE analysis. This tool reports the stressed components in your design and is based on SMOKE parameters defined by the components. The PSpice simulation, followed by SMOKE analysis, can point out which components are stressed for voltage, temperature, etc.

9. Can PSpice use vendor subcircuits (standard Spice or IBIS-AMS models) from vendors as I do not trust transferring component parameters from vendor into your tool? Are there any convergence issues?

Yes, PSpice can consume vendor subcircuit models. In fact, models developed by various semiconductor manufacturers are one of the major sources of models for various circuit simulations. Lack of convergence is a mathematical phenomenon, and models can be one of the causes of the same; however, this cannot be generalized for all vendor models.

10. In an older version, I was able to connect models from PSpice to TI. How can I do it with the new version?

This will be added to an upcoming release.

11. Does PSpice have any output report features and templates?

Within PSpice there is a Tools->Generate Report menu that allows you to export an HTML report for various simulation types like Transient. You can also Copy and Paste the PSpice waveforms directly into applications like Microsoft Word. There are plans to support report templates in an upcoming release.

12. Does PSpice support digital simulation, digital bus, HEX signals, and HEX math?

PSpice is a true mixed-mode simulator, and it supports digital simulation for circuits including digital gates, latches, busses, sources, etc.

Simulation and Settings

1. I have a schematic for a complex PCB, and I need to simulate only a portion of the schematic. Can this be done in PSpice?

Yes, PSpice supports the creation of test benches - where one can selectively include a portion of circuit topology and simulate. You can also make changes to your simulation test bench circuit, without impacting your master PCB schematic.

2. I need to simulate a mechatronics system. Can I use PSpice for that?

Yes, one can use PSpice Designer Plus to simulate a mechatronics system. PSpice Designer Plus enables co-simulation of electrical and mechanical systems. Designers can simulate their designs using the Cadence PSpice analog and mixed-signal simulator, perform MATLAB and Simulink behavioral-level modeling, and utilize all MATLAB post-process analysis, visualization, and measurement functions in a single, integrated system design and debug environment. Click here to learn about Pspice.

3. Can I use PSpice to run AC Analysis for the pre-layout PCB chip caps selection (values, placement, and quantity) for the various power rails?

Yes – PSpice is very effective for simulating frequency domain impedance for a power delivery network (PDN) at the schematic level, which helps you select the appropriate decoupling capacitors before layout. However, it does not capture physical layout effects (e.g. via inductance, plane spreading impedance, etc…) unless explicitly modeled.

4. Sometimes I get convergence errors while simulating a circuit. How do I overcome this?

Turn on Auto-convergence mode, which smartly selects simulation options to achieve convergence.

5. Is there an easy way to set simulator settings for designs?

Based on design topology, one can design a simulation persona - this includes simulator options with values that are likely to make the circuit simulate perfectly. These simulation personas can then be invoked by a command on the circuit - reducing the time involved in setting these options for each design. PSpice, by default, ships 5 simulation personas, one of them is specific for Switching circuits.

6. How can I know if some components in my circuit are going to fail due to electrical stress?

PSpice has various advanced analysis tools - one of them is SMOKE analysis. It essentially uses simulation data and calculates the stressed components in your circuit. So, if there is any component like a Resistor or MOSFET with lower power dissipation rating than required, SMOKE analysis helps in flagging those components so that you can then replace them with components of correct ratings as per design. This saves a lot of cost and time compared to a situation where anything fails or burns out physical hardware.

7. Can a variable be used in the model so that the min/max FET values can be simulated?

Yes. You can sweep model parameter values and with the upcoming PSpice release you can also sweep models themselves. You can automatically run simulations for different models and compare results.

8. Can you perform model parameter sweep in your current design?

This capability will be available in an upcoming release where you will be able to sweep not only model parameters but also sweep across different models.

9. Can you run multiple 'scenarios' with different sets of parameters? (NOT a Monte Carlo that varies all parameters). For instance, maybe I have 10 different runs where I use specific values for 12 different parameters.

Yes. PSpice enables users to perform multi-dimensional what-if analysis and complete design space exploration. PSpice Advance Analysis Parametric Plotter is a dedicated application for design space exploration and result visualization.

10. Let's assume the RAMP pin on the current example is a no connect (NC) pin. I place the NC X in the pin, but PSpice will not simulate unless I connect to a DUMMY Resistor. What am I doing wrong?

If the model includes a function for a pin/port, in this case RAMP, one needs to connect it for simulation. Otherwise, the model circuit would be incomplete - it’s like an open circuit in lab setup.

11. Shouldn’t the PSpice NC part be an infinite resistance?

Not really. If one doesn’t wish to connect a resistance in circuit for pin which is modelled, you can attach a PIN property "FLOAT" and PSpice will automatically take care of this pin. You can also control the impedance you wish to connect with PIN.

12. Can I zoom and pan the simulation graphs using the mouse scroll and mouse buttons?

Yes - you can zoom in and out of the graphs using mouse scroll and zoom features.

13. Can I simulate a portion of a schematic?

Yes. There is an option to create a test bench, and one can simulate a portion of the circuit, or even tweak the circuit such as a different load, etc. See the first question in this section for more details.

14. Are the changes made in the test bench reflected back to the base schematic?

Changes made in test bench stay in the test bench unless you manually bring those changes to your base schematic.

15. Can we simulate EMC/EMI (Electromagnetic Compatibility/Electromagnetic Interference) on PCB?

Yes, one can simulate conducted EMI with PSpice.

16. How do you plot efficiency?

You can write an expression and plot the same.

17. Does a PSpice simulation give component temperatures?

Yes - Smoke analysis is a feature found in OrCAD X Professional Plus or PSpice Designer Plus, used to evaluate electrical and thermal stress on every component in a simulated circuit. Its primary purpose is to detect reliability issues, including overheating, before hardware is built. One can also define and apply derate specifications for various components in circuits. Smoke analyzes the steady state operating conditions from a DC or transient simulation and checks:

  • Power dissipation in each component
  • Maximum rated power
  • Maximum current and voltage
  • Junction temperature based on:
      • User-specified or default ambient temperature
      • Thermal resistant values (e.g., ϑJA from the component model)
18. Can PSpice simulation be done in individual blocks of a hierarchical schematic and in the complete system, which includes multiple complex components?

Yes. Convergence issues are possible in any SPICE simulator. You can use PSpice Auto Convergence to overcome convergence automatically.

19. What about the use of standard SPICE and IBIS-AMI models as part of a PSpice simulation?

PSpice supports import and conversion of IBIS models to SPICE models for simulation. Use PSpice Model Editor to import IBIS models and simulate as SPICE model using PSpice.

20. How can we simulate EMI and EMC?

You need to include source impedance and trace impedance to simulate EMI.

21. How can I verify if the electrical levels (voltage, current, power) are within the rated or maximum conditions of the datasheet? Or even further, to verify if the levels are within the derated conditions?

You can use PSpice SMOKE analysis for the same. Watch our PSpice Webinar for more details.

22. Can we simulate RF, LF, and BLE Communication antenna parameters using PSpice?

Please refer to the Cadence AWR Design Environment Platform for antenna and RF simulation.

23. Can we simulate the entire schematic of a PCB motherboard in PSpice, or do we need to break it down into smaller sections? And if full simulation is possible, does it take a long time to run?

Yes, you can simulate your design with individual sections as well as the entire schematic, so full simulation is also possible. The time it takes to simulate depends on the complexity of the circuit and SPICE models used in the schematic.

PSpice Models

1. Are there many manufacturer models available? How do I link these models to a symbol and place it in the schematic?

If you have a symbol available in the schematic, you can just select it and do Associate PSpice Model, where you can point to the model location, map the model pins to the symbol pins, and attach the model to the symbol.

2. Does PSpice have all the chip capacitor libraries from major chip cap suppliers, like Murata?

Yes, the recently released product update, 24.1 ISR5, includes an additional 5000+ models from Murata.

3. Presumably, you can load PSpice models from most makers. I have occasionally found some don’t work in LTspice, Simetrix, Tina-TI, etc.

This is possible, each simulator has its own syntax for a set of constructs (SPICE model), while 98% syntax is common, a small percentage difference may lead to unsupported models. PSpice has been adding support for more such constructs to make this nearly 100% compatible with any source of SPICE model. Also note that PSpice model support is the responsibility of the supporting simulation vendor, so issues with using PSpice models with LTSpice need to be reported to Analog Devices.

Is there a list of parameters based on component types for PSpice model configuration?

Yes, all the components have been listed in the product document with their SPICE parameters listed. Please refer to the PSpice A/D Reference Guide for more information.

5. Do you have a recorded tutorial for Microcontroller simulation using PSpice?

Yes. You can download it from the Cadence Support portal, and it is also available with PSpice installation.

6. How do you fine tune PSpice models to get accurate results? How do you decide which parameters should be minimum/nominal/maximum? What is recommended?

One can simulate the PSpice models to see their characteristic curves and tweak the parameters as required. It is up to the designer to choose the minimum/nominal/maximum value - PSpice supports all of them.

7. Where can I download PSpice models?

You can download a selection of PSpice models here. Please note that this link does not reflect all available PSpice models. Many component vendors support PSpice models and have links on their respective websites.

8. Can we reuse existing basic schematic symbol and modify for PSpice models?

Yes. One can use Assign Model functionality to map PSpice/SPICE models to update the schematic or library to make it simulation ready.

9. How accurate are the models?

The accuracy of a model depends on the model developer. There are large sets of models supplied by manufacturers such TI, Infineon, Murata, Vishay who claim these to be very accurate.

Others

1. Where can I get the feature comparison sheet of all level modules?

Please reach out to Cadence support for information.

2. Can I use the system capture for simulation, for the SPICE model I need to create by myself?

Yes, the front-end tool, Allegro X System Capture, supports PSpice simulation. The SPICE models for various components are shipped with the installation.

3. Do you have a workshop/tutorial on how to perform frequency response analysis using PSpice?

Yes. In OrCAD X Capture - Use Help>Learning PSpice to view various tutorials and design examples.

4. Is there an AI tool that automatically creates a PSpice model from the datasheet?

Not currently, but it is something we are investigating.

5. How is pre-layout simulation different from post-layout, and why is it important to start early?

It would save you time and cost - you would need to build a fewer number of prototypes, and one can optimize the design better.

6. How is PSpice different from Cadence Virtuoso?

Virtuoso is more suited for IC implementation, whereas PSpice is optimized for PCB simulation.

7. Can we use GaN in Power distribution unit applications?

Yes, GaN switches are increasingly being used in a variety of applications, including power distribution units. PSpice ships various GaN switches, with more being added in upcoming releases.

8. Will there be an option to write code in Python or C/C++ for microcontrollers for digital simulation with microcontrollers like 8051, Arduino, or STM32? And if so, when will it be available with C/C++?

PSpice device Model Interface is available with OrCAD X PSpice designer plus products that enable mode development using C, C++, or system C.

9. Can you share the name of the Cadence tutorial that details the µController simulation?

Look for PSpice Device and System Modeling Tutorial in our Cadence Support Portal.

10. Can you share where I can find the demo PSpice files for learning?

You can get the largest set of application circuit with explanation with your OrCAD X or Allegro X installation - Go to Help > Learning PSpice in OrCAD Capture