PCB Simulation Services
Nine Dot Connects does offer simulation services. It’s one thing to simply list the services, which we so do below; however, we feel that it would be a disservice to you if we did not take a moment to look at the whole picture. There are 2 considerations involved, the first being what to simulate and the second, the cost of simulation.
What to Simulate?
Simulation is the act of modeling the behavior of something. In our line of work, this is related to electrical signals. Regardless of simulation type, all simulations deal with mathematical equations, initial conditions, and the sample steps. This grows rapidly complex by the number of inputs that need to be stimulated and the number of outputs and nodes within the circuit that need to be monitored.
As there is no one universal engine for cars and trucks, there is no one algorithm for simulation tools. Each tool is geared specifically for its intended purpose. For example, in digital simulation, the focus is on the logic state of the outputs and inputs. On an FPGA or large ASIC, each time step (which are generally simulated in steps of nano or pico seconds) may require the reporting of several hundred signals. Given the amount of data that needs to be collected in the time steps given, the focus is on signal level and in some cases, signal delay (if such data is provided). Attempting any signal integrity on all these signals at this granularity would require an enormous amount of computing power in terms of the days, if not weeks. In short, it is not practical.
Whereas, in an analog simulation, the focus is on the signal’s form and integrity. Even then, the more complex the circuit, the more time it takes to simulate it.
In keeping with the vehicle engine analogy, trying to mix analog and digital simulation is the same as asking for a truck with both the torque to pull a large load while expecting the truck to go from 0-60 under 3 seconds. We will not say it is impossible; however, with the current state of technology, it is not feasible.
We must also consider the state of analog simulation. The mainstay simulation method since the 1970s has been SPICE; unfortunately, the use of single letters to represent components in the code construct of SPICE has caused problems with its ability to evolve with the industry. What was once a nice gesture by UC Berkeley to provide the code free of charge has resulted in commercial variations which cannot be fully reconciled with the original Berkeley code. Since the 1990s, there has been no new releases of updates from Berkeley. The industry is completely reliant upon purchasable tools such as PSPICE; and freeware tools such as LTSPICE, XSPICE, TI WebBench and so on.
In addition, it was not developed to handle the frequencies that we are now trying to design and manage. On top of all of this, many companies will not create models for SPICE because it gives away IP related to their buffer designs. This is one of the main reasons Linear Technologies gives away LTSPICE – To provide a free tool to potential customers that allows Linear Technologies to provide SPICE models for their components while protecting their IP. The same is true for the SPICE tool provided by Texas Instruments. As for the high speed elements, it is completely dependent upon what a company decides to provide within the tool that goes beyond the original SPICE engine.
Beyond circuit simulation, there are simulation methods to ensure that the signal integrity is kept and that the board is not going to produce noises that will impact both itself and the surrounding environment. IBIS was developed as an alternative for SPICE in which only the I-V curves of the outputs were provided. Field solvers provide the most accurate information in terms of electromagnetic issues. However, there are cost trade-offs to consider.
When to Simulate?
Though we at Nine Dot Connects are not in the business of chip design, our past collective experiences in chip design gives us good insight. On an ASIC chip level, it makes sense to simulate as much as possible. A design start for a new chip is in the millions of dollars. Respins also cost millions of dollars in addition to the possibility of missing a market window which is measured in weeks, let alone months. In fact, when one really looks at the software design market, most of the simulation tools seemed to be geared for the chip space rather than the board space.
It not to say that board simulation is overkill or unnecessary; however, we must consider the economics of it. The purchase of simulation tools are in the tens of thousands of dollars. In addition, there is a training cost involved in terms of bring the individual up to speed on the fundamental scientific concepts in addition to running the tool and analyzing the data. This could be in the neighborhood of 6 months to a year before the individual is confident in their skills. Though these concepts are introduced in most college undergraduate programs, few engineers grasp the concepts and fewer engineers use it their careers.
Are there alternatives? The answer is yes. In many cases, several planned respins are just as cost effective as the time and cost it takes to purchase such tools. In addition, experience plays a vital role in an engineer’s learning and understanding. What is learned on one project propagates to the next.
The other alternative is to seek a third party to perform the simulation. This can be very useful from the point of view that the simulation will be done by an independent party. However, the cost per hour tends to high ($200+ at the time of this writing) due to cost of purchasing tools and keeping their maintenance subscription current.
Nine Dot connects does have this capability in 2 capacities.
First, we can consult on a design prior to laying it out to ensure that the circuit is going to perform as expected. In addition, we have senior PCB designers who, through their many years of experience, have an intuitive knowledge of the electromagnetic effects and how to mitigate them.
We are certainly looking for ways to help impart this knowledge through training, which we hope to announce in the near future.
In addition, our simulation expert has over 30 years’ experience in addition to writing his own software and publishing numerous article on the subject.