Microcontroller

Thinking of going with PY32F002/3 for cost (<$.20), size (3x3mm), and 1uA sleep. No external parts, other than decoupling caps. Crazy. For now evaluating with the more expensive PY32F030 chip, only $.10 more. No DMA though.

Another option is ST's version of the chip, which starts at $.85 and has lower power sleep, among other things.

STM32G031G8U6

CH570

Positives

• QFN 20 pin package
• $.20
• USB
• DMA, watchdog timer
• BLE, but don't need it

Negatives

• "Off" is still only .3uA
• Less documentation / support
• Low GPIO, 12.

STM32F

About the same price as STM32G03 and in QFN, but only has max sleep of .3uA

Power

Battery

Lithium Ion Capacitor

Very size concious. I was able to get some 0613 (6mm x 13mm) LIC from CDA, but there are some companies that go down to 0307 apparently, half the size! Not sure what cost is yet, but maybe for rev 2. Same spec different companies.

• szgscap_lic_tiny.pdf
• (CapSolution) CS LIC Catalog_200104.pdf
• YMin SLX LIC (some are stocked at LCSC!)

Lithium Ion Battery

LIR series

Surprisingly low mAh!

Airpod form factor (cylindrical)

Sleep states