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MCP7940M-I/SN

MCHPMCP7940M-I/SN

Microchip Technology
Real Time Clock (RTC) IC Clock/Calendar 64B I2C, 2-Wire Serial 8-SOIC (0.154", 3.90mm Width)
Active1,594 in stock
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Overview

The MCP7940M-I/SN is a low-power I2C Real-Time Clock (RTC) and Calendar IC designed for timekeeping in embedded systems. It includes 64 bytes of user SRAM and supports a wide operating voltage range from 1.8V to 5.5V, making it compatible with both battery-operated and line-powered devices. The device features digital timing compensation and dual programmable alarms for flexible event scheduling.

Why Choose This Part

This RTC offers digital trimming with 1 PPM resolution for high-accuracy timekeeping across a wide temperature range. Its extremely low standby current of 1uA helps maximize battery life in portable applications, while the integrated 64 bytes of SRAM provides a convenient place to store non-volatile system parameters without the wear-leveling concerns of EEPROM.

Applications

Data Logging
Providing accurate timestamps for sensor readings and system events in low-power industrial loggers.
White Goods Control
Managing time-of-day schedules and delayed-start features in domestic appliances.
System Maintenance Timers
Tracking runtime intervals and triggering scheduled maintenance alerts in commercial equipment.
Metered Utilities
Maintaining time and date for electricity or water meters to support time-of-use billing.

Key Specifications

Type Clock/Calendar
Features Alarm, Leap Year, Square Wave Output, SRAM
Interface I2C, 2-Wire Serial
Date Format YY-MM-DD-dd
Memory Size 64B
Time Format HH:MM:SS (12/24 hr)
Mounting Type Surface Mount
Package / Case 8-SOIC (0.154", 3.90mm Width)
Voltage - Supply 1.8V ~ 5.5V
Operating Temperature -40degC ~ 85degC
Supplier Device Package 8-SOIC
Current - Timekeeping (Max) 1uA @ 5.5V

Getting Started

To evaluate the MCP7940M, engineers can use the Microchip MCP79410 RTCC PICtail Plus Daughter Board or interface the SOIC-8 package directly to a microcontroller via the I2C bus. Ensure the external 32.768 kHz crystal is matched to a 6-9 pF load capacitance for optimal oscillator stability. Software implementation is straightforward using standard I2C libraries and following the 2-wire serial protocol for register access.

MCP7940 Family

Comparing specs that differ across variants. The current part is highlighted.

Part Number Package Current - Timekeeping (Max) Stock
MCP7940M-I/SN (this part) SOIC-8 1uA 1,594
MCP7940NT-I/MS TSSOP-8 1.2uA 22,374
MCP7940NT-I/SN SOIC-8 1.2uA 32,168
MCP7940MT-I/MNY WFDFN-8 1uA 10,857
MCP7940MT-I/SN SOIC-8 1uA 2,696
MCP7940N-I/P DIP-8 1.2uA 1,254
Also available as: MCP7940N-I/SN, MCP7940N

Also Consider

DS1307 Maxim Integrated / Analog Devices - A widely used alternative with 56 bytes of NV SRAM, though it requires a 5V supply for full operation.
PCF8563 NXP Semiconductors - A popular low-power RTC that offers similar I2C functionality and alarm features in an 8-SOIC package.
MCP79410 MCHPMicrochip Technology - A similar device that adds 128 bytes of EEPROM and an EUI-48 or EUI-64 node identity if non-volatile storage beyond SRAM is required.

Categories

Clocks & Timing > Real-Time Clocks Microcontrollers > Microchip