Now shipping REV 02-00!

What is it?

This is a breakout board for the MCP7940N I2C RTC IC. It breaks out the I2C pins, power input and has an onboard battery holder. There is a 0.1"/2.54mm header and JST SH connector (STEMMA QT and Qwiic compatible!) for the I2C lines. Other pins are broken out into dual row 0.1"/2.54mm headers. Headers come unsoldered.

The MCP7940 is a Real-Time Clock and Calendar IC from Microchip, which includes a backup battery and has a 64 byte SRAM. The non-volatile memory can be used for storing things like calibration data. The design uses a highly accurate 32.768kHz crystal for time keeping. The crystal has a frequency tolerance of +/- 20ppm. The IC itself can be calibrated for tolerance offsets. It includes trimming of +/- 1ppm and range of +/- 129 ppm. All components used are able to be used with an operating temperature range of -40 degC to + 85 degC.

10kOhm pull-up resistors are included on the board. The IC has an operating voltage range of 1.8 to 5.5V, so it is ideal for both 3.3V and 5V systems.

There is an Arduino library for the MCP7940: https://www.arduino.cc/reference/en/libraries/mcp7940/

Why did you make it?

I made this board because I didn't see too many options for this IC and needed it for a home project. A lot of the boards found on sites like Amazon and AliExpress don't use an accurate crystal which can cause the IC to loose accuracy for timekeeping purposes. My boards are also populated with genuine and quality components and each board is tested before shipping.

What makes it special?

The crystal on it is highly accurate. The built-in SRAM is also a nice feature when you need to store a small amount of data. Hand built and made in the USA.

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