MCP79400T-I/MS

Real Time Clock Overview

The MCP79400T-I/MS is a battery-backed I2C Real-Time Clock/Calendar (RTCC) manufactured by Microchip Technology in an 8-lead MSOP package. It operates within a voltage range of 1.8V to 5.5V and supports an industrial temperature range of -40°C to +85°C. The device maintains time using a 32.768 kHz crystal or external clock source, featuring on-chip digital trimming for ±1 ppm resolution. Key electrical parameters include a typical timekeeping current of 1.2 µA at 3.3V from VCC and 925 nA at 3.0V from backup. It includes 64 bytes of SRAM and unprogrammed protected EEPROM.

Real Time Clock Feature Summary

• I2C compatible serial interface with clock rates up to 400 kHz
• Real-time clock/calendar tracking seconds through year with leap year compensation to 2399
• 64-byte battery-backed SRAM and 8-byte protected EEPROM area
• Automatic switchover to battery backup with power-fail timestamp logging

Real Time Clock Applications

• General purpose real-time clocking in embedded systems
• Data logging applications requiring timestamp capture during power loss
• Battery-powered devices needing low standby current consumption

Real Time Clock Procurement Notes

Verify the ordering suffix 'T' indicates reel packaging and 'I' denotes the industrial temperature grade (-40°C to +85°C). Confirm the '/MS' suffix corresponds to the 8-lead MSOP package. Ensure compatibility with the required I2C pull-up resistor values based on the target bus speed.

Real Time Clock Selection Notes

Select this component when an unprogrammed EEPROM is required, as opposed to the MCP79401 which contains pre-programmed EUI-48 addresses. Ensure the application utilizes a 32.768 kHz crystal with a load capacitance between 6 pF and 9 pF. Verify that the system voltage remains within the 1.8V to 5.5V operating range.

Real Time Clock Part Context

This part belongs to the MCP7940X family, which also includes the MCP79401 and MCP79402. The primary distinction lies in the EEPROM content: the MCP79400 has unprogrammed memory, while the MCP79401 and MCP79402 are pre-programmed with EUI-48 and EUI-64 MAC addresses, respectively. All variants share identical pinouts and functional registers.

Real Time Clock Replacement Considerations

The MCP79401T-I/MS and MCP79402T-I/MS are pin-compatible replacements if the specific EUI-48 or EUI-64 address programming is acceptable for the design.