MCP79410-I/SN

The MCP79410-I/SN from Microchip is a highly integrated I2C real-time clock/calendar (RTCC) that combines timekeeping, non-volatile memory, and advanced features in a single 8-pin SOIC package. Beyond basic RTC functionality (seconds through year counting with leap year compensation through 2399), the MCP79410 integrates 64 bytes of battery-backed SRAM for critical parameter storage, 1Kb of EEPROM for persistent data, and a factory-programmed or user-programmable 64-bit unique ID in protected EEPROM space. The digital trimming feature allows software calibration of the crystal oscillator with 1PPM resolution and +/-129PPM adjustment range, enabling precise timekeeping without external components. Two independently programmable alarms can trigger on match of seconds, minutes, hours, day of week, or date, with output on the multifunction MFP pin. The power-fail timestamp feature automatically logs the time when the main power fails and the device switches to battery backup, and again when main power is restored, enabling power-failure event analysis. The automatic battery switchover circuit seamlessly transitions between VCC and VBAT supplies. The clock output feature on the MFP pin supports 4 selectable frequencies (1Hz, 4.096kHz, 8.192kHz, 32.768kHz) for system clocking applications. The MCP79410 is part of the MCP7941x family, where the MCP79411 adds protected EEPROM and the MCP79412 adds additional protected EEPROM space.

The MCP79410-I/SN operates as an I2C-interfaced real-time clock with integrated non-volatile memory. Key subsystems include: (1) RTC Core – a 32.768kHz crystal oscillator drives a chain of BCD counters for seconds, minutes, hours, day, date, month, and year; the oscillator uses an on-chip inverter with external crystal and load capacitors; the digital trimming circuit adjusts the oscillator frequency by periodically adding or removing clock pulses; the 1PPM resolution corresponds to approximately +/-2.6 seconds/month accuracy adjustment; (2) I2C Interface – a standard I2C slave interface (7-bit address 0x6F) supports up to 400kHz Fast Mode; all registers (time, alarms, SRAM, control) are accessed via I2C read/write operations; (3) Dual Alarms – Alarm 0 and Alarm 1 each have their own set of match registers; when the current time matches the alarm settings (on a per-field basis: seconds, minutes, hours, day, or date), the alarm flag is set and the MFP output can be asserted; alarms can be configured for one-shot or repeat operation; (4) Battery Backup – when VCC drops below VBAT, an internal switch connects the RTC core and SRAM to VBAT; the power-fail timestamp circuit captures the current time value at the moment of switchover and stores it in dedicated registers; (5) EEPROM – 1Kb of EEPROM (128 bytes) accessible via I2C provides non-volatile storage that does not require battery backup; a 64-bit unique ID is stored in a protected EEPROM area that can be unlocked with a specific write sequence; (6) Multifunction Pin (MFP) – configurable as alarm output (active-low for either or both alarms), clock output (1Hz/4.096kHz/8.192kHz/32.768kHz), or general-purpose output.

• Industrial data logger: timestamp each data record with RTC, store 64B calibration in SRAM, log power-fail events via timestamp
• Asset tracker: unique 64-bit ID in protected EEPROM identifies each device, dual alarms for periodic wake-up
• Smart meter: digital trimming compensates crystal drift over temperature, power-fail timestamp logs outage duration
• Access control: RTC for time-based access scheduling, 1Kb EEPROM stores access codes, alarm triggers lock/unlock events