Microchip Technology MCP79401T-I/SN

Overview

MCP79401T-I/SN 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, dual programmable alarms, and digital trimming for ±1 ppm resolution. It operates from 1.8V to 5.5V, draws only 1.2 µA at 3.3V during timekeeping, and supports power-fail timestamp logging - used in industrial metering, embedded controllers, and IoT edge nodes requiring accurate, low-power time stamping.

For engineers reviewing the MCP79401T-I/SN datasheet, MCP79401T-I/SN pinout, MCP79401T-I/SN application, or MCP79401T-I/SN equivalent, key selection criteria include I²C interface compliance (up to 400 kHz), backup current ≤925 nA at 3.0V, 32.768 kHz crystal optimization (6–9 pF), ±129 ppm digital trim range, and TSSOP-8 package compatibility with SOIC/MSOP/TDFN footprints.

Technical Context

The MCP79401T-I/SN implements a fully autonomous RTCC subsystem using an on-chip oscillator control loop with digital frequency trimming applied to a 32.768 kHz external crystal. Its register-mapped architecture separates timekeeping (0x00–0x1F), SRAM (0x20–0x5F), and protected EEPROM (0xF0–0xF7) into distinct I²C address spaces (1101111x and 1010111x), enabling concurrent access isolation.

Power management includes automatic switchover between VCC and VBAT (1.3–5.5V) with timestamp capture on both transition edges, while alarm logic supports independent match conditions across seconds, minutes, hours, date, month, and weekday - all configurable via dedicated ALM0/ALM1 registers with mask bits and interrupt flags.

Key Specifications

Pinout & Package

Package: 8-pin TSSOP (lead-free, RoHS-compliant, 3.0 × 4.4 mm body, 0.65 mm pitch).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MCP79400T-I/SN, the MCP79401T-I/SN adds factory-assigned EUI-48™ for plug-and-play network integration; compared with DS3231M+, it trades ±2 ppm TCXO stability for lower power, EEPROM security, and seamless I²C address compatibility in existing Microchip-based designs.

Availability

MCP79401T-I/SN is available at Aetrix Electronics and suitable for industrial metering, medical device logging, and IoT gateway timing applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MCP79401T-I/SN 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 devices, and timing solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The MCP7940X product line delivers highly integrated, low-power RTC/Calendar ICs with embedded memory and alarm functions - designed specifically for resource-constrained embedded systems needing reliable, battery-backed timekeeping without MCU intervention.

FAQ

What is the primary function of the MCP79401T-I/SN?

The MCP79401T-I/SN is a battery-backed I²C Real-Time Clock/Calendar IC that maintains accurate time and date (including leap-year compensation through 2399), stores 64 bytes of SRAM and 8 bytes of protected EEPROM preprogrammed with EUI-48™, and supports dual programmable alarms. It serves as a standalone timing peripheral in systems where host MCU resources are limited or power efficiency is critical.

Does the MCP79401T-I/SN require external load capacitors for its 32.768 kHz crystal?

Yes, the MCP79401T-I/SN requires external load capacitors on X1 and X2 pins to match the crystal's specified load capacitance (6–9 pF). The device does not integrate load capacitance; CX1 and CX2 values must be selected per Equation 5-1 in the datasheet to ensure stable oscillation and meet ±129 ppm trim range specifications.

How does the power-fail timestamp feature work in the MCP79401T-I/SN?

The MCP79401T-I/SN automatically logs the exact time of VCC dropout (in PWRDN registers) and VCC restoration (in PWRUP registers) using internal counters. This occurs during switchover between main and backup power, with timestamps stored in BCD format and accessible via I²C - enabling forensic analysis of power events without host MCU involvement.

Can the MCP79401T-I/SN operate using an external clock instead of a crystal?

Yes, the MCP79401T-I/SN supports external 32.768 kHz clock input on the X1 pin when the EXTOSC bit in the CONTROL register is set. In this mode, X2 is left floating, and the internal crystal oscillator circuit is disabled - useful when system-level clock distribution eliminates need for discrete crystal placement.

What is the significance of the EUI-48™ address in the MCP79401T-I/SN?

The MCP79401T-I/SN has 8 bytes of protected EEPROM preprogrammed with a globally unique EUI-48™ MAC address, compliant with IEEE 802 standards. This enables zero-touch network onboarding in IoT gateways and industrial controllers, eliminating manual MAC provisioning and ensuring cryptographic binding between hardware identity and firmware credentials.