Battery Backed I2C Real Time Clock / Calendar with SRAM, 24HR, 1.8V to 5.5V, SOIC 8 - 

MCP7940N-I/SN is a battery-backed I2C™ real-time clock/calendar with SRAM. It tracks time using internal counters for hours, minutes, seconds, days, months, years, and days of the week. Alarms can be configured on all counters up to and including months. For usage and configuration, the MCP7940N supports I2C communications up to 400KHz. The open-drain, multi-functional output can be configured to assert on an alarm match, to output a selectable frequency square wave, or as a general-purpose output. It is designed to operate using a 32.76KHz tuning fork crystal with external crystal load capacitors. On-chip digital trimming can be used to adjust for frequency variance caused by crystal tolerance and temperature. SRAM and timekeeping circuitry are powered from the backup supply when the main power is lost, allowing the device to maintain accurate time and the SRAM contents.