The MAX31331 ultra-low power, real-time clock (RTC) is a time-keeping device that consumes nominal 65nA timekeeping current, extending battery life. The MAX31331 supports a wide range of 32.768kHz crystals. A crystal with any capacitive loading (CL) spec can be used, which broadens the pool of usable crystals for this device. This device is accessed through an I2C serial interface.The device also features a backup supply pin (VBAT) and automatically switches over to the backup supply (VBAT) when the main supply (VCC) drops below the programmed threshold voltage and the backup supply (VBAT) voltage.Other features include two time-of-day alarms, interrupt outputs, programmable square-wave output, event detection input with timestamping, and a serial bus timeout mechanism. The 32-byte timestamp registers double as RAM storage. The device features a digital Schmitt trigger input (DIN) which can be used to record timestamps and/or generate an interrupt on the falling/rising edge of the DIN signal. The clock/calendar provides seconds, minutes, hours, day, month, year, and date information. A 1/128 second register is available for a sub-second timestamp resolution. The date at the end of the month is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in 24-hour/12-hour format.The MAX31331 is available in lead (Pb)-free/RoHS compliant, 12-bump, 1.66mm x 1.26mm WLP with 0.4mm pitch, as well as a 10-pin 3mm x 3mm TDFN package.The device supports the -40°C to +85°C extended temperature range.ApplicationsMedicalWearablesPortable InstrumentsTelematicsIndustrialIoT