How to Reduce Respins of Your PCB Using SPICE Simulation

One of the most frustrating aspects of any job is when you have to redo work that you thought was already done. Painters don’t like to have to climb back up the ladder to touch up that missed spot on the ceiling, chefs don’t like to re-cook food that is returned by a customer, and PCB design departments don’t want to keep re-spinning board designs. Yet design respins will continue to happen until designer engineers make regular use of circuit simulation software.

Fortunately, there are simulators available that can help design engineers find problems in their circuits before they layout the circuit board. Simulated Program with Integrated Circuit Emphasis, or SPICE, is a common simulation system that can be of great help. Not only will you be able to reduce respins of your PCB using SPICE simulation, but you will be able to realize many other benefits as well.

The Problem: PCB Respins Due to Not Using SPICE Simulation

The usual practice in testing schematic circuitry while in development has been to build a breadboard of the circuit. This gives you the ability to physically see and test the different components and wiring of the circuit, as well as allowing you to make changes and try alternative components and connectivity.

The problem is that long ago circuitry became far too complex to test each individual circuit with a breadboard. Without thorough testing not only are the individual circuits unvalidated, but also the system performance isn’t tested either for interrelated circuitry performance. Without adequate schematic circuit testing before PCB layout, it will all come down to the prototype builds of the circuit board to test the circuitry.

Rarely are boards so simple anymore that they require little or no circuit validation. Instead, the more complex the circuits are, the more levels of testing will be required. One problem could lead to another and, like the Energizer bunny, the testing cycle will keep on going and going and going. This will eventually lead to a lot of respins of the circuit board to find and resolve all the problems with the circuitry if you are relying on PCB prototypes for circuit validation. Fortunately, there are simulation tools available that will allow you to test your circuits before you go to layout with your schematic.

At one time using a breadboard to test your circuits was the only validation method available

The Advantages of Using SPICE

Design engineers have been using SPICE for many years to take the place of breadboarding their circuits. Not only does this eliminate the need to physically wire up circuits on a breadboard, but there are many other benefits as well:

• SPICE will allow the users to check the validity of their schematic circuitry and predict the behavior of those circuits.

• SPICE will also allow users to find unexpected circuit behaviors instead of being surprised by those behaviors later on.

• SPICE will allow users to test multiple levels of circuitry and study that circuitry from different levels. Instead of being strangled by complex system problems when there is only a limited breadboarded circuit in front of them to work with, design engineers can approach whole system problems from a top-down perspective.

• SPICE gives the users the ability to explore design alternatives without having to invest time and money in physical parts and labor to work these circuit alternatives out on a breadboard.

• SPICE provides an excellent tool to perform “what-if” analysis and record those results.

There are a lot of great benefits to using SPICE to simulate your circuitry, let’s take a look now at how SPICE simulation will help reduce your board respins.

Using SPICE tools will reduce the number of prototype PCBs you need for circuit validation

Reducing Respins of Your PCB Using SPICE Simulation

By using SPICE in a top-down approach, design engineers are able to evaluate circuitry problems as a whole and then examine the specific lower level problems. With the lower level problems resolved, the prototype builds of the PCB will then be used to validate the design rather than to test out individual circuits. This will remove the need for many of the more traditional prototype builds that have been done in the past allowing you to focus your prototypes on system validation instead of circuit validation.

With SPICE simulation in place, you will end up saving you both time and money which will help you to get your product through the design phase and out to market sooner.

One of the most productive and cost-effective SPICE tools available is PSpice, part of the Cadence family of tools. Integrated with the schematic capture tools from Cadence, PSpice will be a huge productivity enhancement for your PCB design process.

If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.