The DS3231 is a low-cost, extremely accurate I2C real-time clock (RTC) with an integrated temperature-compensated crystal oscillator (TCXO) and crystal. Thedevice incorporates a battery input, and maintains accu-rate timekeeping when main power to the device is inter-rupted. The integration of the crystal resonator enhancesthe long-term accuracy of the device as well as reducesthe piece-part count in a manufacturing line. The DS3231is available in commercial and industrial temperatureranges, and is offered in a 16-pin, 300-mil SO package.The RTC maintains seconds, minutes, hours, day, date,month, and year information. The date at the end of themonth is automatically adjusted for months with fewerthan 31 days, including corrections for leap year. Theclock operates in either the 24-hour or 12-hour formatwith an AM/PM indicator. Two programmable time-of-day alarms and a programmable square-wave outputare provided. Address and data are transferred seriallythrough an I2C bidirectional bus. A precision temperature-compensated voltage refer-ence and comparator circuit monitors the status of VCCto detect power failures, to provide a reset output, andto automatically switch to the backup supply when nec-essary. Additionally, the RSTpin is monitored as a pushbutton input for generating a reset externally.