RTC with sub-µA timekeeping and wide supply range
The NXP PCF85363ATT/AJ is an I2C real-time clock that tracks time in HH:MM:SS:hh (12/24 hr) and date in YY-MM-DD-dd formats, with a 64-byte RAM for scratchpad or timestamp logging. It draws 0.885 µA max from the main supply at 3.3 V while keeping time — low enough that a 40 mAh coin cell backup runs the clock for over five years before needing replacement.
Supply flexibility and backup battery integration
The main supply accepts 0.9 V to 5.5 V, and the battery input covers the same 0.9 V to 5.5 V range — so a 3 V lithium coin cell or a 1.8 V supercap both work without a level shifter. The part automatically switches to the backup supply when VDD drops below the battery threshold, maintaining timekeeping and alarm functionality during main power loss.
On-chip features that save external components
The integrated watchdog timer can reset a hung microcontroller without a separate external watchdog IC, and the alarm output drives an interrupt or wake-up line directly. Leap-year correction is handled automatically through 2099, so no firmware calendar patch is needed for date rollover in long-life deployments.