I'm trying to design a low power PIR motion sensor, but there seems to be a dearth of information about it. I know how the pyroelectric sensor works, and I know what the waveform looks like, but how do I make a small, low power circuit that can actually detect that? The ideal thing would be to use an existing chip, but it seems like there are so few of those, none of which are really readily available.
I've found a few circuit diagrams:
but as you can see, they vary massively in complexity. Ideally I want the simplest, lowest power, smallest one possible, but I'm lost on where to draw the line. The BISS0001 manages to do it at like 50uA, which I feel like I could not get close to.