MCP7940N-I/ST

Real Time Clock Overview

The MCP7940N-I/ST is a battery-backed I2C Real-Time Clock/Calendar (RTCC) with 64-byte SRAM, manufactured by Microchip Technology. It operates within a supply voltage range of 1.8V to 5.5V and supports backup voltages from 1.3V to 5.5V. The device tracks time using internal counters for hours, minutes, seconds, day of week, date, month, and year, supporting both 12-hour and 24-hour formats. It features dual programmable alarms, an open-drain multifunction pin (MFP), and on-chip digital trimming with ±1 PPM resolution over a ±129 PPM range. The typical timekeeping current is 1.2 µA at 3.3V, with a backup current of 925 nA at 3.0V. It communicates via an I2C interface up to 400 kHz and is qualified to AEC-Q100 standards.

Real Time Clock Feature Summary

• Real-Time Clock/Calendar with leap year compensation through 2399
• 64-byte Battery-Backed SRAM for user data storage
• On-chip digital trimming for oscillator calibration (±1 PPM resolution)
• Dual programmable alarms and versatile MFP output

Real Time Clock Applications

• Industrial systems requiring accurate timekeeping in -40°C to +85°C environments
• Automotive electronics compliant with AEC-Q100 qualification
• Battery-powered devices utilizing automatic switchover to backup supply

Real Time Clock Procurement Notes

Verify the package type matches the specific order code; the 'I/ST' suffix indicates the Industrial temperature range (-40°C to +85°C) and TSSOP-8 packaging. Confirm that the application design accounts for the required external 32.768 kHz crystal and load capacitors, as these are not included with the component. Ensure the I2C bus pull-up resistors are selected appropriately for the operating voltage and desired clock speed.

Real Time Clock Selection Notes

Select the MCP7940N-I/ST when an I2C-compatible RTCC with integrated SRAM and automotive qualification is required. This model is suitable for designs needing power-fail time-stamping and low-power operation down to 1.8V. Consider alternative packages such as MSOP or SOIC if the TSSOP form factor does not fit the PCB layout constraints, while maintaining the same electrical specifications.

Real Time Clock Part Context

The MCP7940N is part of Microchip's family of battery-backed real-time clocks. The '-I' designation specifies the industrial temperature grade, distinguishing it from the extended temperature variant ('-E'). The '/ST' suffix identifies the 8-lead Thin Shrink Small Outline Package (TSSOP). This component integrates timekeeping, memory, and alarm functions into a single low-power IC.

Real Time Clock Replacement Considerations

Direct replacements within the same family include other MCP7940N variants with different package options, such as MCP7940N-I/SO (SOIC-8) or MCP7940N-I/MS (MSOP-8). These alternatives share identical electrical characteristics and pinouts but differ in physical dimensions. Verify that the footprint on the printed circuit board accommodates the specific package style selected.