Active SPI RTC with trickle-charge and alarm
The DS1390U-3+T&R is a real-time clock/calendar from Analog Devices, part of the DS1390 family, communicating over an SPI bus. It tracks time in HH:MM:SS:hh (12/24 hr) and date in YY-MM-DD-dd format, with an integrated alarm, leap-year compensation, and a square-wave output for system timing. A trickle-charger on the backup battery input (1.3V–3.7V) keeps the timekeeping alive when the main 2.7V–3.3V supply drops.
125 µA timekeeping at 2.7V–3.3V
Maximum timekeeping current is 125 µA across the full 2.7V–3.3V supply range — important for battery-backed designs where quiescent draw directly affects cell life. Packaged in a 10-TFSOP/MSOP (0.118", 3.00mm width) with a 10-uMAX/uSOP supplier device package — a compact footprint for space-constrained PCBs.