Another topic of discussion during today’s design review was the use of separate boards for our ADC and DAC modules. Clearly, our mentor was of the opinion that connectors should be avoided as much as possible, because of their high impedance. Most importantly, pins tend to get corroded over time, leading to ever increasing impedance.
Unfortunately, we cannot really put everything on one board if we want to keep our device small enough. Therefore, we will have to use multiple boards. But when doing so, we should be really careful about their design. For example, we should use connectors that provide pins with a pitch that is as wide as possible.
Currently, we are planning to use SO-DIMM connectors, which use a 1 mm pitch, but we might be able to find ones that provide an even wider pitch. Another strategy could consist in using parallel lanes for signals that mandate a very low impedance. I was originally worried that such parallel lanes could induce unwanted side effects, but my mentor did not seem overly concerned about that.
Last but not least, putting power regulators on the backplane seems to be a really bad idea, since it would increase the distance between them and their target inputs. Therefore, regulators should be mounted directly on the modules, or on sideboards attached to the modules through standard DIP headers.