More and more design operations become automated. These changes give many benefits like effectiveness, minimal errors and less routine operations to designers. Modern electronic equipment require very precise planning as devices shrink to minimal sizes, operation power increases and also have to fit to it external design requirement. So designing is a very complex task where without smart CAD software would be almost impossible to do.
When designing a new electronic device you have to deal with several areas that is necessary to make device reliable and attractive device. All of these areas usually are done on particular CAD system. Most common CAD based electronic specific task are:
Mixed Analog-digital device modeling;
Programmable Logic modelling and synthesis;
HF circuits and electromagnetic modeling;
Chip topology modeling.
Each of these modeling and designing processes require different skills and knowledge.
Lets go through each to see their specifics and what CAD systems are used to automate related tasks.
Mixed Analog-digital device modeling
This is most common task among electronic engineers. Today almos all Electronic CAD systems have circuit capture tools that enable to create circuits and model them. In most programs circuit modeling is done via SPICE(Simulation Program with Integrated Circuit Emphasis). SPICE standard is created in Berkeley university in 1975. SPICE is a set of functions that allows to describe electronic devices and simulate them. So you can simulate electronic circuits with computer without having real prototype board. Using SPICE you have flexibility and speed. Because it is possible to change parameters or change a circuit itself and simulate under different parameters changes and other circumstances. On real board you can’t do many changes and even sometimes you haven’t ability to measure all characteristics. Few CAD software packages that include SPICE are:
Altium Protel DXP Design Explorer
Protel DXP Design Explorer is considered to be a professional tool that allows to create project from beginning to the end. Here you can create, simulate circuits, develop PCB. It also gives ability to develop FPGA devices. Tool not recommended to hobbyists and beginners.
Cadence PSPICE A/D included in to ORCAD package
ORCAD is also very flexible tool-set that is loved in academic environment because of its various simulation and analysis.
It is quite flexible and has and number of simulation result analysis functions. It also has valuable tool PSPICE optimiser that allows to optimise circuits according to various criteria.
This is another powerful tool for circuit simulation developed by National Instruments Workbench Group. Electronic Workbench Simulator environment is very intuitive and easy to use and have many circuit analysis abilities like DC Transfer Function, Small Signal Analysis, Distortion Analysis, Noise Analysis, Sensitivity Analysis, Transient, Fourier analysis and more. Electronic Workbench comes in Multisim package which includes PSPICE simulator, PCB design tools, D breadboarding and so on.
There are lots of more packages that simulates circuits like Proteus, which have ability to simulate Microcontrollers, or even open-source projects like Ngspice: https://ngspice.sourceforge.net/ Tclspice: https://tclspice.sourceforge.net/ .
Programmable Logic modelling and synthesis
Programmable logic is more and more becoming common part in any system. It has many benefits comparing to microprocessor systems like ability to parallel operations and this way to increase performance significantly. Especially in DSP systems. Programmable logic circuits are programmed in PLD, CPLD, FPGA chips. Usually these logical functions are programmed using HDL language like VHDL or Verylog. There are quite many packages to work with Programmable logic devices like:
Altium programa PeakFPGA;
PLD module in Protel DXP;
Cadence modules in ORCAD;
Programmable software mostly is accessible from chip manufacturers list of FPGA design software you can find here.
HF and microwave circuits modeling
More complex tasks are when frequencies goes UP. Because main reason is that in High Frequency circuits currents are flowing differently in inductor volume and also there are noises very actual. To model Microwave circuits there has to be Maxwell problems solved because SPICE modeling doesn’t work here. There are several Microwave studios available to work with HF circuits:
Microwave Office combines linear and non-linear circuit analyses, design, multilayer electromagnetic modeling.
Ansoft HF modeling packages include various products like Hig-Frequency products(Ansoft Designer, HFSS, Nexxim), Signal Integrity products(DesignerSI, Q3D Extractor, SIwave, TPA), EM products(Maxwell 2D, Maxwell 3D, Simplorer, PEexpert, Rmexpert)
It solves full 3D volume problems by using Finite element method to find a solution. Results are displayed graphically what makes it attractive.
Functional modeling is high level design modeling where you have to model systems in object level without going too deep in to circuit level. As one suitable tool for this I would mention Matlab Simulink. Matlab is very universal package as it is a mathematical modeling tool, but it has a big number of standard libraries with practically unlimited abilities.
Matlab can simulate practically any object including mechanical, electrical, financial, neural, etc. This is why it is very popular tool among most engineers. If not present, you can create any model in matlab.
PCB design is one of the last steps in project. It purpose to get working prototype what was simulated previously. This part has a big competition which tool is better. Maybe this is why so many tools are available now like: Altium P-CAD, Altium PROTEL, Cadence ORCAD, EAGLE CAD, Mentor Graphics Expedition PCD and more. These packages compete which is better in autoplacing, autorouting, signal integrity. Bigger packages like OrCAD and Protel are dealing with footprint databases. Protel can work as a client-server architecture which has centralized element base.
In higher integrity circuits there are special routing module SPECTRA used which enables customisation of tracing according to various parameters. But again there is no algorithm created yet that can be trusted. Last word is engineers. Usually he has to fine-tune PCB before it can be produced.
PCB thermal analysis
Thermal analysis of PCB is done when serial production is going to be done. This is complex task as it require many parameters on how different chips dissipate power what materials are used and so on. There are several CAD packages like BETAsoft, Sauna(Thermal Solutions).
Chip topology modeling
This is little different modeling areas as it takes IC modeling itself. IC manufacturers use expensive and specialized software which cost big money. Integral chips can contain from few hundreds to millions of element in one crystal so task complexity is huge. Companies like Intel, AMD spend billions of dollars in equipment to make new processors.
CADENCE produce packages for designing IC’s using various technologies. Software is more oriented to digital IC design and simulation.