 MCP7940M-ISN device package |
 MCP7940M-ISN schematic symbol |
An RTC (real time clock) is an integrated circuit which contains a very precise and accurate clock for time keeping in electronic circuits. The RTCs are very widely used in computers, laptops, mobile phones, servers, and other embedded systems. In fact they are used in all those digital circuits which need accurate time keeping functionality. One of the major advantages of RTCs is that they include a backup power source and keep on functioning even when the main power is cut off. The backup power source used to be Lithium based batteries in older RTCs however super-capacitors are mainly used in latest RTCs. The other features of RTC include low power consumption and accurate time keeping. RTCs use a 32.768 kHz crystal oscillator for clock pulse generation. The typical accuracy of these clocks is around 5 parts per million. Apart from standalone ICs, RTCs are also commonly integrated into microcontroller packages.
What is MCP7940M-I/SN？
The MCP7940M-I/SN is a real time clock/calendar IC developed by MICROCHIP. This RTC is capable of tracking time in hours, minutes, seconds, days, months, years, and day of week using internal timers and counters. This chip can be configured using I2C interface with a maximum data rate of 400 kHz. The open drain output is a multi-function pin which can be used to generate a square wave of adjustable frequency or can be used as a general purpose output. The RTC is designed to operate using 32.7687 kHz crystal oscillator along with external capacitors.
Pin Configuration
The pin configuration of the MCP7940M-I/SN real time clock is given in the table below:
| Pin number | Pin name | Pin description |
| 1 | X1 | Oscillator input pin |
| 2 | X2 | Oscillator output pin |
| 3 | NC | Not connected |
| 4 | Vss | Ground pin |
| 5 | SDA | Bidirectional serial data pin |
| 6 | SCL | Serial clock pin |
| 7 | MFP | Multi-function output pin |
| 8 | Vcc | Power supply pin |
Features
- Provides hours, minutes, seconds, day, month and year
- Compensation for leap years up to year 2399
- 12/24 hour modes
- On-chip digital trimming and calibration
- Dual programmable alarms
- Clock output with selectable frequency
- Alarm and general purpose output
- I2C serial communication interface
- Wide input voltage range
- Low power consumption
- Automatic power sensing and switching
Applications
The applications of MCP7940M-I/SN real time clock are provided as following:
- Single board computers
- PC/laptop motherboards
- Instrument clusters
- Automotive electronics
- Avionic systems
- Smart phones and tablets
- Programmable logic controllers
- Telecom equipment
- Embedded systems
Specifications
The major technical specifications of the MCP7940M-I/SN real time clock IC are provided as following:
- Terminals: 8
- Package: SOIC-8
- Max input voltage: 6.5V
- Time keeping current: 1.2uA
- Max junction temperature: 150o
- ESD rating: 4000V
- Oscillator frequency: 32.768 kHz
- Max I2C clock frequency: 400kHz
How MCP7940M-I/SN work?
The MCP7940M-I/SN is a real time clock IC from MICROCHIP. This RTC is very commonly used in laptops, motherboards, consumer electronics, telecom systems, automotive applications and embedded systems. This RTC chip is capable of providing very accurate data about seconds, days, months, years and dates. The MCP7940M-I/SN contains a backup power source which allows it to keep functioning for extended periods of time even when the main power source is shut off. This IC can be interfaced to the microcontrollers and microprocessors using I2C interface.
A typical application circuit of the MCP7940M-I/SN is given in the schematic diagram below:
MCP7940M-ISN application circuit
MCP7940M-I/SN Related Products Prices
MCP7940M-I/SN
Parts Mfr. Description Stock Prices Buy Now
IC RTC CLK/CALENDAR I2C 8-SOIC 750 RFQ 
IC RTC CLK/CALENDAR I2C 8-SOIC 5000 $0.584 Lowest 
Microchip Technology Battery-Backed I2C Real-Time Clock 120 $0.667 Lowest
MCP79410T-I/SN Microchip Technology IC RTC CLK/CALENDAR I2C 8-SOIC 261 $0.677 Lowest
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