The MCP7940N series of low-power Real-Time Clocks (RTC) uses digital timing compensation for an accurate clock/calendar, a programmable output control for versatility, and a power sense circuit that automatically switches to the backup supply. Using a low-cost 32.768kHz crystal, it tracks time using several internal registers.For communication, the MCP7940N uses the I2C™ bus. The clock/calendar automatically adjusts for months with fewer than 31 days, including corrections for leap years. The clock operates in either the 24-hour or 12-hour format with an AM/PM indicator and settable alarm(s) to the second, minute, hour, day of the week, date or month. Using the programmable CLKOUT, frequencies of 32.768, 8.192 and 4.096kHz and 1 Hz can be generated from the external crystal.The device is fully accessible through the serial interface while VCC is between 1.8V and 5.5V, but can operate down to 1.3V for timekeeping and SRAM retention only.

Timekeeping

  Battery-Backed Real-Time Clock/Calendar (RTCC)

  Hours, Minutes, Seconds, Day of Week, Day, Month, Year

  Leap year compensated  to 2399

  12/24 hour modes

  On-Chip Digital Trimming/Calibration

  1 PPM Resolution

  ±129 PPM Range

  Dual Programmable Alarms

  Versatile Output Pin

  Clock output with selectable frequency

  Alarm output

  General Purpose output

  Power-Fail Time-Stamp

  Time logged on switchover to and from Battery Backup

  64 Bytes Battery-Backed SRAM

  2-Wire Serial Interface, I2C™Compatible

  I2C Clock Frequency up to 400 kHz

Low-Power

  Wide Voltage Range

  Operating Voltage 1.8V to 5.5V

  Backup Voltage 1.3V to 5.5V

  Low Typical Timekeeping Current

  Automatic Switchover to Battery Backup