SPI RTC with backup battery management
The Maxim Integrated DS1390U-3+ is a serial real-time clock (RTC) that keeps time as YY-MM-DD-dd and HH:MM:SS:hh in 12/24-hour format. Communication is over SPI. An integrated trickle-charger maintains a backup battery or supercap on the Vbat rail, so the clock holds through a main-supply dropout. The alarm output and square-wave generator can drive a host interrupt or toggle a logic line without polling. Supply range is 2.7 V to 3.3 V for the main rail; the battery backup input accepts 1.3 V to 3.7 V. Timekeeping current peaks at 125 µA over the full supply range, which keeps the load on the backup source low.
Housed in a 10-lead TFSOP/MSOP (3.00 mm body width). The supplier device package is 10-uMAX/uSOP.