Microchip Technology MCP79401-I/ST

Overview

MCP79401-I/ST from Microchip Technology is a battery-backed I²C Real-Time Clock/Calendar (RTCC) IC with integrated 64-byte SRAM, 8-byte protected EEPROM preprogrammed with EUI-48™ MAC address, digital trimming (±1 ppm resolution), dual alarms, and power-fail timestamping. It operates from 1.8V to 5.5V, draws just 1.2 µA at 3.3V V_CC, and maintains timekeeping accuracy across -40°C to +85°C industrial temperature range.

For engineers reviewing the MCP79401-I/ST datasheet, MCP79401-I/ST pinout, MCP79401-I/ST application, or MCP79401-I/ST equivalent, this page delivers verified technical context, exact pin functions, real-world timing use cases, and validated alternative parts for embedded timekeeping, power-loss logging, and secure device identification in industrial control and IoT edge nodes.

Technical Context

The MCP79401-I/ST implements a fully autonomous RTCC subsystem using an internal 32.768 kHz oscillator circuit optimized for 6–9 pF crystals, with on-chip digital trimming (±129 ppm range, ±1 ppm step) to compensate for crystal tolerance and temperature drift. Its I²C interface supports up to 400 kHz clock rate and uses two distinct slave addresses: 0xD8/0xD9 for RTCC/SRAM access and 0xA8/0xA9 for EEPROM operations.

Power management includes automatic switchover between V_CC and V_BAT at 1.3–1.7 V threshold, with separate timestamps logged for both power-down and power-up events. The multifunction pin (MFP) serves as configurable alarm output, selectable-frequency square-wave generator (32.768 kHz, 1024 Hz, 32 Hz, 1 Hz), or general-purpose open-drain output - all controlled via the CONTROL register.

Key Specifications

Pinout & Package

Package: 8-pin SOIC (Small Outline Integrated Circuit), 150 mil width, surface-mount, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar real-time clock/calendar applications.

Compared with MCP79400-I/ST, the MCP79401-I/ST adds factory-programmed EUI-48™ for plug-and-play device identity, while DS3231SN#T&R trades EEPROM and MAC features for superior oscillator stability - making MCP79401-I/ST optimal for secure, low-power, identity-aware embedded systems.

Availability

MCP79401-I/ST is available at Aetrix Electronics and suitable for smart metering, industrial PLCs, medical infusion pumps, and networked sensor nodes requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for MCP79401-I/ST includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Microchip Technology Inc. is a leading provider of microcontrollers, analog components, and timing solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The MCP7940X product line delivers highly integrated, battery-backed RTC/Calendar ICs designed specifically for industrial, medical, and IoT applications demanding reliable timekeeping, secure device identification, and robust power-fail resilience.

FAQ

What is the primary function of the MCP79401-I/ST?

The MCP79401-I/ST is a battery-backed I²C Real-Time Clock/Calendar IC that maintains accurate time and date (hours, minutes, seconds, day, month, year, weekday) with leap-year compensation through 2399. It integrates 64-byte SRAM, 8-byte protected EEPROM preprogrammed with EUI-48™, dual alarms, digital trimming, and power-fail timestamping - all in a single 8-pin SOIC package. The MCP79401-I/ST serves as a self-contained timing engine for embedded systems requiring persistent, low-power timekeeping.

How does the MCP79401-I/ST handle power loss and recovery?

The MCP79401-I/ST automatically switches to V_BAT when V_CC drops below 1.3–1.7 V, preserving RTCC operation and SRAM contents. Crucially, it logs exact timestamps for both power-down (PWRDN registers) and power-up (PWRUP registers) events - enabling forensic analysis of brownout duration and system behavior. This dual-timestamp capability is intrinsic to the MCP79401-I/ST and requires no host MCU intervention or additional firmware logic.

What is the significance of the EUI-48™ address in the MCP79401-I/ST?

The MCP79401-I/ST includes 8 bytes of factory-programmed EUI-48™ MAC address in its protected EEPROM, providing a globally unique, immutable hardware identifier. This eliminates the need for external ID storage or host-based provisioning, accelerating device onboarding in IoT networks and simplifying regulatory compliance (e.g., FCC ID linkage). Unlike generic serial numbers, the EUI-48™ format ensures compatibility with IEEE 802 networking standards - a feature exclusive to the MCP79401-I/ST within the MCP7940X family.

Can the MCP79401-I/ST operate with an external clock instead of a crystal?

Yes, the MCP79401-I/ST supports external 32.768 kHz clock input on the X1 pin. When enabled via the EXTOSC bit in the CONTROL register, the internal crystal oscillator is disabled and X2 is left floating. This mode bypasses crystal load capacitance tuning and oscillator startup delays, offering deterministic timing initialization - useful in systems where clock jitter or board layout constraints make crystal placement impractical. All other RTCC functions (alarms, timestamping, SRAM) remain fully operational.

What are the key differences between MCP79401-I/ST and MCP79400-I/ST?

The MCP79401-I/ST and MCP79400-I/ST share identical pinout, RTCC functionality, SRAM, alarms, and power management. The sole functional difference is that the MCP79401-I/ST includes factory-programmed EUI-48™ in its 8-byte protected EEPROM, while the MCP79400-I/ST ships with unprogrammed EEPROM. Both parts support custom EEPROM programming, but only the MCP79401-I/ST guarantees a preassigned, globally unique MAC address - making it ideal for secure, standards-compliant device identity deployment.