The DACx311 contain four separate modes of operation. These modes are programmable by setting two bits (PD1 and PD0) in the control register. Table 8-1 shows how the state of the bits corresponds to the mode of operation of the device.

When both bits are set to 0, the device works normally with a standard power consumption of typically 80 μA at 2 V. However, for the three power-down modes, the typical supply current falls to 0.5 μA at 5 V, 0.4 μA at 3 V, and 0.1 μA at 2 V. Not only does the supply current fall, but the output stage is also internally switched from the output of the amplifier to a resistor network of known values. The advantage of this architecture is that the output impedance of the part is known while the part is in power-down mode. There are three different options: the output is connected internally to GND either through a 1-kΩ resistor or a 100-kΩ resistor, or is left open-circuited (High-Z). Figure 8-3 illustrates the output stage.

Figure 8-3 Output Stage During Power-Down

All linear circuitry is shut down when the power-down mode is activated. However, the contents of the DAC register are unaffected when in power-down. The time to exit power-down is typically 50 μs for AV_DD = 5 V and AV_DD = 3 V.