• Vin - this is the power pin. Since the sensor chip uses 3VDC, we have included a voltage regulator on board that will take 3-5VDC and safely convert it to 3VDC. To power the board, give it the same power as the logic level of your microcontroller - e.g. for a 5V micro like Arduino, use 5V.
• 3Vo - this is the 3.3V output from the voltage regulator, you can grab up to 100mA from this if you like
• GND - common ground for power and logic

• SCL - the I2C clock pin, connect to your microcontroller I2C clock line.
• SDA - the I2C data pin, connect to your microcontroller I2C data line.
• STEMMA QT - These connectors allow you to connectors to dev boards with STEMMA QT connectors or to other things with various associated accessories

By default the I2C address on the MAX44009 breakout will be 0x4A. An alternative address of 0x4B is available by soldering closed the Addr jumper on the bottom of the breakout.

INT - the interrupt pin. It is an open-drain interrupt. To use, connect the pin to a GPIO pin on your microcontroller and configure as pull up.

Above the left STEMMA QT connector there is a small green ON power indicator LED. When the breakout is powered this LED will turn on. 

On the back of the MAX44009 breakout there is a jumper with a small trace between two pads that can be cut to disable the ON power indicator LED on the board.