I²C RTC with trickle-charge backup
The DS1340U-33+ is a Clock/Calendar real-time clock from Analog Devices, communicating over an I²C (2-Wire Serial) bus. It keeps time in YY-MM-DD-dd date format and HH:MM:SS (24 hr) time format, with leap-year compensation built in. A trickle-charger on the backup battery input means the RTC can maintain timekeeping from a rechargeable cell or supercap when main power drops — useful for data-loggers and metering gear that need timestamp retention through brief outages.
Supply and timekeeping budget
The battery-backup input accepts 1.3 V to 5.5 V, so a 3 V lithium coin cell or a 1.5 V alkaline cell both work. Timekeeping current maxes at 150 µA at 5.5 V — low enough that a 220 mAh coin cell lasts over 60 days in backup mode, assuming the RTC is the only load on the battery. The 8-uMAX/uSOP package (3.00 mm wide) is a standard footprint for pick-and-place; no tombstoning risk if the pad geometry matches the recommended land pattern.