Microchip Technology MCP79400T-I/MNY

Overview

MCP79400T-I/MNY from Microchip Technology is a battery-backed I²C Real-Time Clock/Calendar (RTCC) IC with integrated 64-byte SRAM and unprogrammed 64-bit protected EEPROM. It maintains time across hours, minutes, seconds, day of week, date, month, and year with leap-year compensation to 2399, operates from 1.8V–5.5V, draws just 1.2 µA at 3.3V, and supports dual programmable alarms - used in industrial control panels requiring accurate timestamping during power loss.

For engineers reviewing the MCP79400T-I/MNY datasheet, MCP79400T-I/MNY pinout, MCP79400T-I/MNY application, or MCP79400T-I/MNY equivalent, key selection criteria include its ±1 ppm digital trimming resolution, power-fail timestamp logging, open-drain multifunction pin (MFP) for alarm/square-wave output, I²C interface up to 400 kHz, and TDFN-8 package compatibility with space-constrained embedded designs.

Technical Context

The MCP79400T-I/MNY implements a fully autonomous RTCC using an internal 32.768 kHz oscillator circuit optimized for 6–9 pF crystals, with on-chip digital trimming (±129 ppm range, ±1 ppm resolution) to correct frequency drift. Its timekeeping registers are buffered to prevent rollover errors during reads, and all values are stored in BCD format.

Power management includes automatic switchover between VCC and VBAT (1.3V–5.5V), with dedicated power-fail timestamp registers (PWRDN/PWRUP) that log exact time of backup activation and primary supply restoration. The I²C interface uses two distinct slave addresses: 0xD8/D9 for RTCC/SRAM and 0xA8/A9 for EEPROM, with separate unlock sequences required for protected writes.

Key Specifications

Pinout & Package

Package: 8-pin 2×3 mm TDFN (exposed pad, optional VSS connection).

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS3231M+ and PCF8563T, the MCP79400T-I/MNY uniquely combines field-programmable trimming, dedicated power-fail timestamp registers, and protected EEPROM in a single TDFN-8 package - making it optimal for industrial systems requiring traceable, tamper-resistant time and identity management.

Availability

MCP79400T-I/MNY is available at Aetrix Electronics and suitable for industrial control panels, smart energy meters, medical infusion pumps, and building automation controllers requiring stable component supply across long production lifecycles.

Supply support for MCP79400T-I/MNY 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 is a U.S.-based semiconductor manufacturer specializing in microcontrollers, analog devices, and timing solutions, with a focus on reliability and long-term product availability.

The MCP7940X family is designed for embedded systems needing autonomous, battery-backed timekeeping with data integrity - targeting industrial, medical, and utility metering applications where timestamp accuracy and power-loss resilience are mandatory.

FAQ

What is the oscillator configuration flexibility of the MCP79400T-I/MNY?

The MCP79400T-I/MNY supports both external 32.768 kHz crystal (with X1/X2 pins) and external clock input (via X1 only). Crystal mode uses on-chip digital trimming for ±1 ppm resolution; clock mode disables internal oscillator via EXTOSC bit. Both configurations maintain full timekeeping functionality and power-fail timestamp logging in the MCP79400T-I/MNY.

How does the MCP79400T-I/MNY handle power transitions between VCC and VBAT?

The MCP79400T-I/MNY automatically switches to VBAT when VCC drops below 1.3–1.7V (VTRIP range), preserving RTC registers, 64-byte SRAM, and oscillator operation. It logs exact timestamps of both switchover (PWRDN registers) and recovery (PWRUP registers). The MCP79400T-I/MNY continues timekeeping with 925 nA typical backup current at 3.0V VBAT.

Can the protected EEPROM in the MCP79400T-I/MNY be used for secure device identification?

Yes - the MCP79400T-I/MNY includes 8 bytes (64 bits) of protected EEPROM accessible only after a documented unlock sequence (writing specific values to EEUNLOCK register). This prevents accidental overwrites and makes it suitable for storing EUI-48/EUI-64 equivalents or custom identifiers. Unlike MCP79401/MCP79402, the MCP79400T-I/MNY ships unprogrammed, allowing end-user customization.

What are the I²C addressing and memory map distinctions in the MCP79400T-I/MNY?

The MCP79400T-I/MNY uses two I²C slave addresses: 0xD8/D9 (R/W) for RTCC registers (0x00–0x1F) and SRAM (0x20–0x5F), and 0xA8/A9 (R/W) for protected EEPROM (0xF0–0xF7). Address ranges outside these - including 0x60–0xEF and 0xF8–0xFF - are unimplemented and generate NACK. This separation enforces secure access control in the MCP79400T-I/MNY.

Does the MCP79400T-I/MNY support alarm functionality with flexible masking?

Yes - the MCP79400T-I/MNY features two independent alarms (ALM0/ALM1) with per-field masking bits (e.g., ALM0MSK0–ALM0MSK2). Each alarm can trigger on seconds, minutes, hours, weekday, date, or month - enabling precise event scheduling (e.g., "alarm every Monday at 09:00"). Alarm output is routed to the MFP pin, configurable as open-drain interrupt or square-wave signal in the MCP79400T-I/MNY.