MCP79521-I/MS

The MCP795XX is a low-power Real-Time Clock/ Calendar (RTCC) that uses digital trimming compensation for an accurate clock/calendar, an interrupt output to support alarms and events, a power sense circuit that automatically switches to the backup supply, non-volatile memory for safe data storage and several enhanced features that support system requirements.

Along with a low-cost 32,768 kHz crystal, this RTCC tracks time using several internal registers and then communicates the data over a 5 MHz SPI bus that is fast enough to support a programmable millisecond alarm.

The device is fully accessible through the serial interface, while V_cc is between 1.8V and 3.6V, but can operate down to 1.3V through the backup supply connected to the VBAT input for timekeeping and SRAM retention only.

As part of the power sense circuit, a time saver function is implemented to store the time when main power is lost and again, when power is restored to log the duration of a power failure.

Along with the on-board serial EEPROM and battery backed SRAM, a 128-bit protected space is available for a unique ID. This space can be ordered preprogrammed with a MAC address, or blank for the user to program.

This clock/calendar automatically adjusts for months with fewer than 31 days including corrections for leap years. The clock operates in either 24-hour or 12-hour format with AM/PM indicator and settable alarm(s). Using the external crystal, the MFP pin can be set to generate a number of output frequencies.

• Timekeeping Features:
• Real-Time Clock/Calendar:
  • Hours, Minutes, Seconds, Hundredth of Seconds, Day of Week, Month, Year, Leap Year
• Crystal Oscillator requires External 32,768 kHz Tuning Fork Crystal and Load Capacitors
• Clock Out Function:
  • 1Hz, 4.096 kHz, 8.192 kHz, 32.768 kHz
• 2 Programmable Alarms
• Programmable open drain output - Alarm or Interrupt
• On-Chip Digital Trimming/Calibration:
  • +/
  • 255 PPM range in 1 PPM steps
• Power-Fail Time-Stamp @ Battery Switchover:
  • Logs time when V_cc fails and V_cc is restored Low-Power Features:
• Wide Operating Voltage:
  • V_cc: 1.8V to 3.6V
  • VBAT: 1.3V to 3.6V
• Low Operating Current:
  • V_cc Standby Current < 1uA @ 3V
  • VBAT Timekeeping Current: <700nA @ 1.8V
• Automatic Battery Switchover from V_cc to