Just wanted to say that everything in this article about the MCU, capacitors and diodes is spot on. (I don't do work with coin cell batteries, but I do have experience with using very small rechargeables and very small solar panels.)<p>To add to it, don't use zener diodes for over-voltage protection. They are extremely leaky. And if you need high value MLCC capacitors you are better off making them yourself from a stack of (more common) 10uF ceramic caps.
Articles like these are great. For those working with ultra-low power MCUs, it's a gold mine of knowledge, data, and wisdom. For everyone else (like me), it finds value as an inspiration. The article stands as an example of what good engineering looks like; the kind of attention to detail and depth of thoughtfulness we should strive to pour into our own projects.