Datasheet

AD5320
Rev. C | Page 13 of 20
POWER-DOWN MODES
The AD5320 contains four separate modes of operation. These
modes are software-programmable by setting two bits (DB13
and DB12) in the control register.
Tabl e 5 shows how the state
of the bits corresponds to the mode of operation of the device.
Table 5. Modes of Operation for the AD5320
DB13 DB12 Operating Mode
0 0 Normal Operation
Power-Down Modes
0 1 1 kΩ to GND
1 0 100 kΩ to GND
1 1 Three-State
When both bits are set to 0, the part works with its normal power
consumption of 140 μA at 5 V. However, for the three power-down
modes, the supply current falls to 200 nA at 5 V (50 nA at 3 V). Not
only does the supply current fall, but the output stage is also inter-
nally switched from the output of the amplifier to a resistor net-
work of known values. This has the advantage 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 through a 1 kΩ resistor, the output is connected
internally to GND through a 100 kΩ resistor, or it is left open-
circuited (three-state). The output stage is illustrated in
Figure 27.
RESISTOR
STRING DAC
RESISTOR
NETWORK
POWER-DOWN
CIRCUITRY
V
OUT
00934-026
AMPLIFIER
Figure 27. Output Stage During Power-Down
The bias generator, output amplifier, resistor string, and other
associated linear circuitry are 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 2.5 μs for V
DD
= 5 V and 5 μs for V
DD
= 3 V
(see
Figure 21).