What this RTC brings to the board
The Maxim Integrated DS1308U-33+ is a serial real-time clock that tracks time in HH:MM:SS (12/24 hr) and date in YY-MM-DD-dd format, with leap-year compensation built in. It communicates over an I²C (2-wire) serial interface, making it a straightforward add-on for any microcontroller with an I²C port. The part includes 56 bytes of NVSRAM for storing configuration or calibration data, and a programmable square-wave output that can serve as a system tick or alarm indicator. The supply range spans 3V to 5.5V on the main rail, so it works equally well in 3.3V or 5V logic systems without a level shifter. A separate battery-backup input accepts 1.3V to 5.5V, allowing a coin cell or supercapacitor to keep the clock running during main power loss. Timekeeping current draws between 125µA and 200µA at 3V to 5.5V — modest enough for battery-backed designs, though not the ultra-low-power tier of dedicated RTCs with sub-µA sleep modes. The operating temperature range of -40°C to 85°C qualifies it for industrial environments: outdoor telecom cabinets, factory-floor controllers, HVAC systems, and automotive cabin applications. The 8-uMAX/uSOP package (3mm body width) fits tight layouts and is rework-friendly under hot air — the exposed pad is small, so a standard 260°C profile lifts the part cleanly without cooking adjacent components.
Package and mounting
The DS1308U-33+ comes in an 8-uMAX/uSOP (also known as 8-MSOP with 0.118" / 3.00mm width). It is a surface-mount part, and the small body means low thermal mass — a hot-air station at 300°C to 320°C with moderate airflow will reflow the solder in about 5 seconds.
Lifecycle and sourcing posture
The DS1308U-33+ is listed as Active (current production) and ROHS3 compliant.