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Promenade develops software for medical devices, which often contain complex electronics. We have seen faulty electronic designs derail projects, causing software delays and rewrites, sometimes with spiraling costs and timelines. More often than not, the mistake could have been caught early on by taking the time to review the design prior to build. In this blog, I will discuss the review process and list some common problems that can be averted by having your new electronic design professionally reviewed.
Design Functional Check: Do all designed circuits work as intended? Sometimes designers connect circuits incorrectly and are blind to their mistakes. With many parts, pins, and nets, wires can get crossed (literally) and your design intent can be misrepresented in the schematic connections. An astute reviewer can in many cases catch these types of connection errors simply because the design is fresh from their perspective.
Schematic Symbol Check: Does the schematic symbol match pin-for-pin to the datasheet? Does the part number being used have the correct footprint? It is very easy to make mistakes when building schematic symbols – especially parts with hundreds of pins. A detailed review of a new design should include a comparison between the component datasheet pinout and the schematic symbol to ensure that all pins are included, and that the names and numbers all line up.
Netlist/Schematic Comparison: CAD software doesn’t know (or care) what you are designing or how it should be connected. In some tools, it is easy to draw a circuit on the page that looks correct visually but is not producing the correct netlist. For the hour or three it takes to print out the netlist and manually compare it to the schematic with a highlighter, It is well worth the time if it can prevent even one wrong connection.
Single Node Nets Check: Many design software packages can create a list of single node nets by pushing a button. This is rarely used and extremely valuable. Especially on larger designs, it is easy to put a label on a connection on one page and just forget or mislabel the matching connection on another page. A Single Node Nets Check can catch these kinds of mistakes.
Footprint Dimensional Check: If you have any new parts in your library, you really want to check them prior to build. By the time your bare boards are done and your assembler has partly built your boards and realizes that your new part footprint is the wrong size, you have already spent weeks on the build and thousands of dollars or more in boards and parts that may need to be scrapped.
FCC Emissions and ESD Testing: Most electronic assemblies will sooner or later require FCC Emissions and ESD Testing. A comprehensive design review includes looking for specific design features that maximize the likelihood of success at the lab. These design features include bypass capacitors on all connector power or DC level pins, transient voltage suppressors on all sensitive signals – especially on the pins that will be accessible after the enclosure is installed, and component placement/routing check of all high speed switching signals. This type of review also includes a check for the proper line widths, dielectric, layer spacing and via placement for intended impedances and looks for high speed routes that might run over splits in the ground plane!
Component Stock Check: What good does it do to finish a new design and get ready for build, if you can’t get all the parts? In many designs if even one IC is not in stock, it can delay a project by weeks or even months waiting for that part to come in. Much better to do your stock check prior to releasing boards for build, if for nothing more than to at least pre-order the long lead parts.
Why is it that there is no time to do the design right (and review it ahead of time), but somehow there is always time (and money) to respin the design if needed? Often new product designs are on a tight timeline and budget designed to avoid disappointing investors and missing marketing/sales windows, making it tempting to skimp on the review process. Having your design professionally reviewed is not just a good idea, but can be a hugely beneficial decision that can help keep your project on track, saving both development time and money.
