MCP79400-I/ST

Real Time Clock Overview

The MCP79400-I/ST is a battery-backed I2C Real-Time Clock/Calendar (RTCC) from Microchip Technology, housed in an 8-lead TSSOP package. It operates within a voltage range of 1.8V to 5.5V and supports industrial temperatures from -40°C to +85°C. The device maintains time using a 32.768 kHz crystal or external clock input, featuring on-chip digital trimming with ±1 ppm resolution. Key specifications include a typical timekeeping current of 1.2 µA at 3.3V and backup current of 925 nA at 3.0V. It integrates 64 bytes of battery-backed SRAM and unprogrammed protected EEPROM.

Real Time Clock Feature Summary

• Real-Time Clock/Calendar with leap year compensation through 2399
• On-chip digital trimming for frequency calibration (±129 ppm range)
• Dual programmable alarms with versatile multifunction output pin
• Power-fail timestamp logging for switchover events

Real Time Clock Applications

• Industrial systems requiring accurate timekeeping under varying temperatures
• Data logging equipment needing power-fail event tracking
• Embedded devices utilizing I2C communication for low-power RTC functions

Real Time Clock Procurement Notes

Verify the specific suffix 'I/ST' corresponds to the Industrial temperature range (-40°C to +85°C) and TSSOP-8 package as defined in the datasheet. Confirm that the 'MCP79400' variant contains unprogrammed EEPROM, distinct from the pre-programmed EUI addresses found in MCP79401/MCP79402 models. Ensure compatibility with the required I2C pull-up resistor values based on the operating voltage.

Real Time Clock Selection Notes

Select this component when an unprogrammed protected EEPROM area is required for custom data storage alongside standard RTCC functionality. The MCP79400 differs from the MCP79401 and MCP79402 by lacking factory-preprogrammed EUI-48 or EUI-64 MAC addresses. Designers must account for external load capacitors (6-9 pF recommended) connected to X1 and X2 pins to ensure oscillator stability.

Real Time Clock Part Context

This part belongs to the MCP7940X family of battery-backed RTCCs. While sharing core timing features with the MCP79401 and MCP79402, the MCP79400 specifically provides user-writable protected EEPROM without pre-assigned network identifiers. All variants share identical pinouts and register maps for timekeeping and SRAM access.

Real Time Clock Replacement Considerations

The MCP79401T-I/ST and MCP79402T-I/ST are functional substitutes within the same family, differing only in the presence of preprogrammed EUI-48 or EUI-64 addresses in their protected EEPROM sections. Other packages such as SOIC-8 or MSOP-8 are available for the same electrical specifications.