Optimizers and cad tools still cannot replace raw intuition and common sense when it comes to analog design

I know there have been many advances in software development for use in design projects. The digital design landscape has permanently been altered by the use of sophisticated software tools for use in design. Design tasks that used to take months can now be completed in days. Although these tools can still provide erroneous results if the setups are incorrect or the models and assumptions are flawed, the errors have vastly been reduced to the point of becoming an exception and not the norm.

With attention to detail, adequate models, and some skilled implementation, the tools used in new digital designs have sped up the design process significantly and with reduced human errors. The use of place and route software tools have also made completing large digital layouts as easy as running scripts for place and route with interactions for static timing analysis for meeting critical setup and hold requirements for digital blocks.

Is this the same for analog design? Are there equivalent tools for designing and completing layouts for analog blocks? I have seen over the years tools often called optimizers to do the work of skilled analog design engineers. Many of the tools have made significant progress in helping designers make faster and timelier decisions. However, I do not believe that the time of replacing the analog engineer is here and won't be for some time. Now it is true that many of the optimizers and placement tools have made significant improvements, however, I do not believe that the current state of the tools can replace an engineer’s raw intuition for designing complex analog blocks.

Although I have said that the use of cad tools such as optimizers should not be used for the design of complex analog designs or complex layouts, I do believe that optimizers do have their place for low level simple analog design blocks.

These low level simple blocks that have loose or less stringent specifications I believe are appropriate for use with analog optimizers for design and layout.

However, the opposite is not true when it comes to complex analog design. As a senior colleague said to me one time “you need to be able to walk with the electrons.” It is when we are faced with difficult analog design challenges that the notion or idea of “walking with the electrons” enables engineer’s to solve difficult and tough design problems and layout constraints.

Often times the appropriate solution requires different topologies or innovation. This cannot be handled by an optimizer that will optimize based on a given set of parameters and a given circuit topology. The optimal solution to the problem may need an innovative combination of known topologies or as I said the invention of new circuits. These types of tradeoffs must be made by seasoned engineers that can think out of the box and come up with new ways to solve these difficult problems. Sometimes simple common sense recognition of whether or not a particular topology is appropriate is needed.

I guess one may argue that with enough power and area a tool could make an existing topology work. I do not believe the outcome from such a design proposal is an acceptable solution as real estate and power on the new technologies is expensive. Ultimately this procedure that produces such sub optimal results will meet resistance from senior leaders once they understand the costs that such a brute force approach using a substandard topology will result in for the final design and layout.

So, I believe the seasoned analog design engineer is safe for the time being, but there are innovative software engineers trying to crack the problems associated with inferior and less sophisticated solvers for analog design and layout.

Furthermore, many companies are working tirelessly to improve the state of the art for these type of solvers and have made significant headway in this respect. Therefore, the best advice I can offer is to be diligent, stay creative, read alternate solutions of how similar analog design challenges were solved, and ensure that you have the bandwidth to stay relevant by creating appealing solutions that are low in power and area and meet the needs of the product.

One last item, analog design engineers always want to strive for realizing analog designs with lots of margin which his appropriate in certain cases. However, be careful about adding too much margin that can cost significant power and area – risk tolerance should be part of your thinking. Ultimately, a seasoned analog designer should clearly understand the risk/reward tradeoffs with the solutions to the analog circuits they are creating and design appropriate circuits that meet the needs of the product without significant overhead.

How have cad tools changed your design strategy?

Do you believe they are practical for analog design?

1 comment on “Optimizers and cad tools still cannot replace raw intuition and common sense when it comes to analog design

  1. Scott Elder
    May 12, 2016

    While you'll get no argument from me about the common sense aspect of analog design, I have to pause a bit when it comes to design margin.

    A company is well rewarded if their part is robust beyond expected usage corners.  You can be certain that the customer will test the device beyond the limits just to gain confidence.  They will not baby it within the specs.  Is the part 1mV from total failure or 1V?  Got to test beyond the limits to find that out.

    If a board designer inadvertently shorts the output of a device late on a Friday, comes back on a Monday and sees the part has failed, invariably the part will be deemed not robust.  Which engineer is going to keep track of all the finite details as troubleshooting unfolds looking for THEIR mistake?  The part will be deemed the culprit simply because it is new.  That's just the way it is.

    If it is early in the design-in process, many times the engineer will move on to the next candidate part.  No engineer will risk their career on releasing a design with parts that they deem not robust.  It becomes a shouting contest between the marketing team that needs the lower priced part and the engineering team that wants to avoid volume risk.

    Same thing holds true for hot-tempered meetings at the key customer's site when field returns cause customer management to initiate a production hold.  The full design team will be called upon to display all the “dirty laundry” during the design and qualification testing.  If there is even a hint of a problem, the company will pay a huge price re-running qualification or doing whatever the customer decides is necessary to regain confidence.

    Credibility is everything when it comes to selling products where the customer has no ability to look “under the hood.”  Its all about trust and building a reputation that your company's products are well engineered.

    On the other hand, if your company sells based on lowest price, don't worry.  The customer's marketing team will be on your side.

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