What the ISL12022MIBZ brings to a timekeeping design
The ISL12022MIBZ is a Clock/Calendar RTC with an I²C (2-wire serial) interface, packing 128 bytes of on-chip SRAM for user data logging or calibration constants alongside the timekeeping registers. It tracks time in HH:MM:SS (12 or 24 hour) and date in YY-MM-DD-dd format, with built-in alarm, daylight savings, and leap year handling — no firmware math for February 29th.
Supply voltage, battery backup, and timekeeping current
Timekeeping current is 14 µA to 15 µA max at 3 V to 5 V — low enough that a CR2032 coin cell with 225 mAh capacity theoretically backs it up for over a year, though self-discharge and the alarm pull-down will reduce that in practice.