Part Number: MCP7940N-I/SN

Manufacturer: Microchip Technology


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Technical Specifications of MCP7940N-I/SN

Datasheet  MCP7940N-I/SN datasheet
Category Integrated Circuits (ICs)
Family Clock/Timing – Real Time Clocks
Manufacturer Microchip Technology
Packaging Tube
Part Status Active
Type Clock/Calendar
Features Alarm, Leap Year, Square Wave Output, SRAM
Memory Size 64B
Time Format HH:MM:SS (12/24 hr)
Date Format YY-MM-DD-dd
Interface I2C, 2-Wire Serial
Voltage – Supply 1.8 V ~ 5.5 V
Voltage – Supply, Battery 1.3 V ~ 5.5 V
Current – Timekeeping (Max) 1.2μA @ 3.3V
Operating Temperature -40°C ~ 85°C
Mounting Type Surface Mount
Package / Case 8-SOIC (0.154″, 3.90mm Width)
Supplier Device Package 8-SOIC

MCP7940N-I/SN Introduction

Microchip Technology’s MCP7940N-I/SN is a highly flexible real-time clock (RTC). It is made to work in various settings, from industrial and automotive to home electronics. This post will dive deeply into the MCP7940N-I/functionality SNs and features and present a comprehensive guide to getting the most out of it.

MCP7940N-I/SN General Description

Hours, minutes, seconds, days, months, years, and days of the week are all counted by the MCP7940N Real-Time Clock/(RTCC) Calendar’s internal counters. Alarms can be set for any duration, from a few seconds to a few months. The MCP7940N is equipped with I2C communication up to 400 kHz, which can be used for setup and operation. This open drain, the general-purpose output, can be used to do anything from assert on an alert match to produce a square wave at a frequency set by the user to just function as an output.

The MCP7940N will work with an external crystal load capacitor and a tuning fork crystal set to 32.768 kHz. On-chip digital trimming can be utilized to compensate for frequency variation due to crystal tolerance and temperature. When the main power goes out, the device’s SRAM and timekeeping circuits are kept running by the backup power supply, so the time and data in SRAM are not lost. The power-fail time stamp records when the device begins using the secondary power source and when the primary power source is restored.

MCP7940N-I/SN Features

  • The device’s 20ppm oscillator ensures precise timing over its operating temperature range. The calendar will be adjusted automatically for leap years, as the device can recognize them.
  • The MCP7940N-I/SN has a dual time zone system that allows it to function in a 12-hour or 24-hour mode.
  • The device is compatible with Daylight Saving Time (DST) and can make the necessary adjustments automatically.
  • The MCP7940N-I/built-in SN’s power failure detection circuit senses when the mains power is cut off and automatically switches to battery power.
  • Battery Backup: Thanks to its battery backup technology, the device can keep working even if the main power is cut off. The battery can last up to a decade, depending on its use.
  • The MCP7940N-I/SN can be set to go off an alarm at a specified time or interval. You can choose between an interrupt and a square wave in the alarm output.
  • The device includes a stopwatch function for keeping track of time.

Additional features

● Memory Features

Non-volatile data, including timestamps, event logs, and system configurations, can be stored in the MCP7940N-I/64 SN’s bytes of EEPROM memory. I2C provides access to the EEPROM memory, which may be programmed in byte and page write modes.

● Low-Power Features

To preserve power, the MCP7940N-I/SN can function in low-power modes. It consumes only 350nA in standby mode and 1.2A under normal operating conditions. Thanks to its backup function, the device can run for up to 10 years on a single CR2032 battery.

● I2C Interface

The MCP7940N-I/SN exchanges data with the host computer via an I2C interface. I2C, or the Inter-Integrated Circuit, is a serial interface that uses only two wires and may be used with various microcontrollers. The device can communicate via the slower I2C protocol (100kHz) or, the faster I2C protocol (400kHz).

Functional Description

The MCP7940N is a highly integrated Real-Time Clock and Calendar, and its operation is described below (RTCC). An internal, low-power oscillator keeps track of the day, date, month, and year in addition to the standard time formats of seconds, minutes, and hours. With the MCP7940N, you get 64 bytes of general-purpose SRAM. Two alarm modules can be used to generate interruptions at predetermined periods based on various comparison criteria.

Inaccuracies in crystals can be corrected by using digital trimming. In the event that primary power is lost, the MCP7940N will immediately switch to backup power through the backup supply input and an integrated power switch. When the primary power goes out and comes back on, the time-stamp module records both events. All of the MCP7940N’s built-in modules can be accessed through the RTCC’s configuration and Status registers.

● Modification of an Oscillator’s Current Path

The MCP7940N has a choice between two oscillator setups: external crystal and external clock input.

The MCP7940N uses a 32.768 kHz crystal or external clock source to keep accurate time. Seconds, minutes, hours, days, dates, months, and years are all recorded in their own individual registers. If a month has 30 or 30 fewer days, the MCP7940N will update itself automatically and account for leap years from 2001 through 2399.

A simple binary value representing the year is used for storage. The 12/24 bit allows you to switch between the 12-hour and 24-hour time systems. Values for days of the week range from 1 to 7, increasing by 1 at midnight and can be represented in any way the user sees fit (i.e., the MCP7940N does not require 1 to equal Sunday, etc.). The registers keep track of the time and date in the form of binary-coded decimal (BCD) data. The MCP7940N will faithfully display the correct time and date even using the secondary power source.

Two separate alarms can be set off on the MCP7940N. Every alarm can go off at a predetermined time or on a recurring schedule (every minute, hour, day, week, or month).


With precise time and date information, low power consumption, and advanced features like alarm and stopwatch functions, the MCP7940N-I/SN is a highly flexible and dependable real-time clock and calendar device serving various applications. However, for optimum performance, you must strictly adhere to the device’s datasheet and power supply requirements and extensively test it in your particular application.

The MCP7940N-I/I2C SN’s interoperability means it can be seamlessly included in many setups while providing accurate timekeeping and solid performance. The MCP7940N-I/SN is a great option for any application requiring industrial automation, consumer electronics, or automotive system control.

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