The MCP79402 is a low-power I²C RTCC that tracks seconds, minutes, hours, day-of-week, date, month, and year, with leap-year compensation up to year 2399 and selectable 12/24-hour formats. It is designed for embedded systems that require reliable time retention and event logging.

A key feature is its automatic switchover to battery backup. When the primary supply is lost and a backup source is present, timekeeping and SRAM contents are maintained, and the device logs the switch events using a power-fail timestamp. The protected EEPROM (8 bytes) supports storing critical identifiers or configuration data with a robust write-unlock sequence.

Variant note: MCP79402 includes a factory-programmed EUI-64™ identifier. MCP79401 provides a factory-programmed EUI-48™, and MCP79400 is unprogrammed.

MCP79402-I/SN indicates the Industrial temperature version in SN package, which is an 8-lead SOIC (3.90 mm body) surface-mount package. Always confirm the land pattern and mechanical dimensions with the official package drawing.

The SOIC-8 pinout integrates the crystal connections, I²C interface, backup supply, and a multifunction output pin for alarms or clock output.

• X1 / X2: 32.768 kHz crystal pins
• VBAT: Backup battery supply input
• VSS: Ground
• VCC: Main power supply
• MFP: Multifunction open-drain output (alarm / clock output / GPIO)
• SCL: I²C serial clock
• SDA: I²C serial data

Alternative RTC devices are typically selected based on interface, backup requirements, package constraints, and firmware compatibility. The following parts are commonly considered in RTC designs:

• MCP79400 - Same family; protected EEPROM unprogrammed
• MCP79401 - Same family; includes factory-programmed EUI-48™
• DS1307 - I²C RTC used in basic timekeeping designs (verify feature differences and supply ranges)
• PCF8563 - Low-power I²C RTC (confirm register map and backup scheme)
• DS3231 - I²C RTC with integrated oscillator/temperature compensation (different footprint/behavior)

Note: Always validate register map, timing behavior, supply ranges, and PCB footprint before approving any substitute for production.

Microchip Technology Inc. develops microcontrollers, analog, and embedded system solutions used widely across industrial, automotive, communications, and consumer markets. The MCP7940X family provides low-power RTCC functionality with memory resources for embedded designs.