This library is intended for the MCP47x6 series of DAC devices that includes MCP4706 (8-bit DAC), MCP4716 (10-bit DAC) and MCP4726 (12-bit DAC) and it uses the I2C library that can be downloaded from down below. If you want to know more about it visit I2C and TWI library for AVR.
MCP47x6 DAC pinout
1 - VOUT: this is the DAC analog output voltage. In Normal mode, the DC impedance of the output pin is about 1Ω. In Power-Down mode, the output pin is internally connected to a known pull-down resistor of 1 kΩ, 125 kΩ, or 640 kΩ. The VOUT pin can drive up to 100 pF of capacitive load in parallel with a 5 kΩ resistive load. It is recommended to use a load with RL greater than 5 kΩ. Driving large capacitive loads can cause stability problems for voltage feedback op amps.