The AD5666 is a low power， quad， 16-bit， buffered voltageoutput DAC. The part operates from a single 2.7 V to 5.5 V supply and is guaranteed monotonic by design. The AD5666 has an on-chip reference with an internal gain of 2. The AD5666-1 has a 1.25 V 5 ppm/°C reference， giving a full-scale output of 2.5 V; the AD5666-2 has a 2.5 V 5 ppm/°C reference， giving a full-scale output of 5 V. The on-board reference is off at power-up， allowing the use of an external reference. The internal reference is turned on by writing to the DAC. The part incorporates a power-on reset circuit that ensures that the DAC output powers up to 0 V （POR pin low） or to midscale （POR pin high） and remains powered up at this level until a valid write takes place. The part contains a power-down feature that reduces the current consumption of the device to 400 nA at 5 V and provides software-selectable output loads while in power-down mode for any or all DAC channels.