MCP7940M-I/MS

Real Time Clock Overview

The MCP7940M-I/MS is a low-power 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 industrial temperatures from -40°C to +85°C. The device features a 2-wire I2C interface with clock rates up to 400 kHz, 64 bytes of SRAM, and dual programmable alarms. Timekeeping includes leap year compensation through 2399, 12/24 hour modes, and on-chip digital trimming with ±1 PPM resolution.

Real Time Clock Feature Summary

• Real-Time Clock/Calendar with leap year compensation to 2399
• 64-byte user-accessible SRAM
• Dual programmable alarms with flexible comparison options
• On-chip digital trimming for frequency calibration (±129 PPM range)
• Versatile multifunction pin (MFP) for alarm, CLKOUT, or general purpose output

Real Time Clock Applications

• Battery-backed systems requiring accurate timekeeping
• Data logging devices needing timestamping
• Embedded systems with I2C master controllers
• Industrial equipment operating in wide temperature ranges

Real Time Clock Procurement Notes

Verify the ordering suffix 'MS' corresponds to the 8-lead MSOP package. Confirm the 'I' suffix indicates the industrial temperature range (-40°C to +85°C). Ensure the specific revision matches the design requirements, as register maps may vary between revisions. Check for any specific handling instructions related to humidity sensitivity if applicable.

Real Time Clock Selection Notes

Select this component when an I2C-compatible RTCC with integrated SRAM is required. The MSOP package is suitable for space-constrained surface-mount designs. Consider the MCP7940N variant if battery backup switching functionality is needed, as the MCP7940M lacks this feature. Verify that the external crystal load capacitance requirements (6-9 pF) align with the available crystal components.

Real Time Clock Part Context

The MCP7940M is part of Microchip's low-cost RTCC family. It shares functional similarities with the MCP7940N but differs in the absence of a backup switching circuit. Other variants in the series include SOIC, TSSOP, PDIP, and TDFN packages. The device is designed to replace discrete RTC solutions by integrating the oscillator, calendar logic, and memory into a single chip.

Real Time Clock Replacement Considerations

Public confirmed substitute part numbers are not provided in the source material. Designers should verify pin compatibility and register mapping if considering alternative RTCCs from other manufacturers.