RTC with I²C bus and NVSRAM
The DS1308U-18+T is a real-time clock (RTC) from Analog Devices that tracks time in HH:MM:SS (12/24 hr) and date in YY-MM-DD-dd format, with leap-year compensation through 2100. Communication is over an I²C (2-wire serial) bus, making it a straightforward add-on to any microcontroller with a spare I²C port — no extra GPIOs needed for a parallel interface. The 56 bytes of NVSRAM are battery-backed via a separate supply pin (1.3V to 5.5V), so timekeeping and stored data survive a main power loss without external supervisor logic.
Timekeeping current is 100µA typical at 1.89V, rising to 200µA at 5.5V — low enough that a standard CR2032 coin cell backs it for years, but the battery drain at higher VCC should be factored into the shelf-life calculation.
Package and rework considerations
Housed in an 8-uMAX/uSOP (3.00 mm wide, 0.118" pitch), this is a small-outline package with exposed leads — no thermal pad underneath, so it reflows cleanly with a standard hot-air profile and the pin 1 indicator is clearly marked on the top mold. The 8-TSSOP and 8-MSOP footprints are interchangeable for this part; both measure 3.00 mm body width, so a single PCB land pattern serves either variant. RoHS3 compliant — no lead in the solder finish, so no special handling beyond standard ESD precautions during rework.