Best Practices in Circuit Design Using Multisim and LabVIEW

Welcome to ‘Best Practices in Circuit Design Using Multisim and LabVIEW’ - a seminar for engaging the design

engineering community for improving circuit design methodology by promoting the use of joint simulation and applied measurements.

1

2

Multisim - Integrated Design Flow

National Instruments has an integrated design platform, represents the best practices through integrated design, simulation

and test.

NI Multisim is our integrated capture and simulation environment.

NI Ultiboard is a flexible layout and routing tool.

NI LabVIEW a graphical programming language to allow you to access measurement data on a PC through virtual

instrumentation.

3

Multisim Overview

Multisim is a graphical based schematic capture application with an integrated spice

simulator. It has thousands of components with built in spice capability allowing an

engineer to quickly generate a design and simulate the functionality. The spice simulator

has many built in analyses allowing an engineer to vary operation over a set of conditions.

In addition Multisim can directly import LabVIEW VIs so that they can be used in process

with the simulation engine.

Ultiboard - Rapid PCB Layout and Prototyping

The Multisim tool can also directly integrate into NI Ultiboard for rapid PCB layout or

generate net lists to be used with other popular PCB design packages. NI Ultiboard

provides an exceptional set of features at low cost for quickly developing a small piece of a

larger design or the entire PCB.

4

SPICE Primer – Examples

The netlist will consist of components that have been defined in SPICE. SPICE components include several different types

of electrical devices that can be simulated.

In SPICE all the network elements are entered in a specific format; let’s examine the netlist created by the above voltage

divider circuit:

– Any text after the asterisk (*) is ignored by SPICE.

– Every element is defined between terminals called nodes (in this example we have 3 nodes: 0, 1 and 2).

– The DC voltage source (V1) is defined by ‘v’ followed by whatever name you may want to use (in this case ‘V1’).

– The next number is the node corresponding to the positive side of the DC source (‘1’); ‘0’ is the negative side.

–’12’ is the magnitude of the voltage source.

–Similarly, we’re defining R1 and R2.

Subcircuit Model

A subcircuit is simply a shell that contains any combination of primitive devices (basic SPICE models) and

.MODEL statements, which combine to create a more complex circuit.

For example, the subcircuit model from the slide is definition of a bipolar junction transistor.

5

SPICE and Virtual Instrumentation

While Multisim is a full featured circuit simulation tool, you can greatly expand the circuit

analysis capabilities of our software by developing custom interfacing to NI LabVIEW and

leveraging the measurement and hardware interfacing capabilities in our graphical

programming environment.

There are 2 ways of interfacing to LabVIEW:

1) Develop a custom LabVIEW instrument (.VI), place the instrument library inside of a

specialized Multisim directory and the custom instrument will be accessible to anyone

using Multisim (see examples on ni.com). LabVIEW is required to build the VI, but is

not required when running the instrument inside of Multisim.

2) Programmatically control the Multisim simulation engine through LabVIEW by

downloading the Multisim Connectivity Toolkit and using the functions to graphical

program a hybrid test-simulation interface. LabVIEW is required for both programming

and running the developed application (unless a stand alone EXE is built from

LabVIEW).

Interactive Simulation – LabVIEW Instruments

With the latest version of Multisim, NI Virtual Instruments based on LabVIEW can be added to themeasurement and stimulus capability of the tool – greatly expanding and enhancing the designingand testing capabilities available to the design engineer.

Key concepts:

•Extend capabilities of Multisim with LabVIEW programming•LabVIEW is only needed to create the custom instrument•Downloadable from ni.com/devzone•Unlimited Measurement possibilities

More info:How To Create a LabVIEW Based Virtual Instrument for NI Multisimhttp://zone.ni.com/devzone/cda/tut/p/id/5635

6

7

LabVIEW Toolkits

In addition to the native functionality of LabVIEW, many toolkits are available for LabVIEW.

Depending on the specialty area that you may be working on, LabVIEW provides

functionality for filter design, control design, modulation, spectral analysis and sound and

vibration analysis among others.

You can readily leverage any of the NI LabVIEW toolkits for use within the Multisim

environment to immediately expand your circuit analysis capabilities.

Virtual Prototype

Thus as a part of an integrated platform between design and virtual test – we can improve simulationand overcome such an issue. The virtual prototype effectively plugs a real world source into thesimulation environment – so that our design SPICE based circuit is reacting to a real-world noisy, ordomain specific signal.

This can be done in a National Instruments platform – by using the virtual instrumentation ofLabVIEW to connect to hardware and record a real world signal. Therefore a real power source canbe analyzed and saved to a standard measurement format. Once saved to a LabVIEW format it canbe exported to the simulation environment of Multisim where, due to a native file format transfer thatreal signal that we have saved can now be used as a stimulus in simulation. This means we cananalyze how our circuit performs under real conditions. Changes that would normally not be seen tillafter prototyping can now be iterated upon within the Multisim simulation environment.

8

National Instruments – Custom Designs

No need to start your complete design from scratch – NI has many quality

engineered OEM or prototyping products to get your product ideas quickly

implemented – in both hardware and software. The fact that you can also

easily modify and expand the functionality by creating your own specialty

circuit interface in Multisim means you can quickly and reliably get your ideasand products to market.

9

Hardware Design References in Multisim

Many hardware design references are now available and more are being

added as National Instruments grows the prototyping product line.

The NI hardware products are easily programmed using on our LabVIEWdevelopment environments.

10

Multisim - Recap

Multisim, Ultiboard and LabVIEW are an exceptional solution for circuit

simulation, PCB prototyping and virtual testing.

Use NI tools for rapid prototyping and simulation to avoid problems and toget to market quickly.

11

1212

NI Multisim – More Information

Thank you for looking at National Instruments to meet your engineering design needs.

Although we introduced some basic but essential topics in Multisim design – you may have

more questions. To speak to a technical expert directly, call 1.800.263.5552 and one of our

technical representatives will be able to assist you. If you are located outside of North

America please check out www.ni.com/niglobal for local contact information for your area.