What do you think about using the T1616’s TCD with ULP ? Adventures in TinyAVR 1-Series - #29 by gchart
Gchart measured 500uA at 5V, probably would be <400uA at li-ion voltages, which is more reasonable than than the 1~2mA at normal system clock, it’s stilla bit high but would be ok for an optional richer high aux mode.