AD5665BCPZ-R2 datasheet(30/36 Pages) AD

30 / 36 page

AD5625R/AD5645R/AD5665R, AD5625/AD5665

Data Sheet

Rev. C | Page 30 of 36

POWER-DOWN MODES

Command 100 is reserved for the power-up/power-down

function. The power-up/power-down modes are programmed

by setting Bit DB5 and Bit DB4. This defines the output state of

the DAC amplifier, as shown in Table 15. Bit DB3 to Bit DB0

determine to which DAC or DACs the power-up/power-down

command is applied. Setting one of these bits to 1 applies the

power-up/power-down state defined by DB5 and DB4 to the

corresponding DAC. If a bit is 0, the state of the DAC is

unchanged. Figure 70 shows the contents of the input shift

When Bit DB5 and Bit DB4 are set to 0, the part works normally

with its normal power consumption of 1 mA at 5 V. However,

for the three power-down modes, the supply current falls to

480 nA at 5 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. This allows the

output impedance of the part to be known while the part is in

power-down mode. The outputs can either be connected

internally to GND through a 1 kΩ or 100 kΩ resistor or be left

open-circuited (three-state) as shown in Figure 67.

Note that the 14-lead TSSOP models offer the power-down

function when the part is operated with a VDD of 3.6 V to 5.5 V.

The 10-lead LFCSP models offer the power-down function

when the part is powered with a VDD of 2.7 V to 5.5 V.

Table 15. Modes of Operation for the AD56x5R/AD56x5

DB5

DB4

Operating Mode

Normal operation

Power-down modes

1 kΩ pull-down resistor to GND

100 kΩ pull-down resistor to GND

Three-state, high impedance

Figure 69. Output Stage During Power-Down

The bias generator, output amplifier, resistor string, and other

associated linear circuitry are shut down when 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 4 μs for VDD = 5 V or VDD = 3 V.

Figure 70. Power-Up/Power-Down Command

RESISTOR

NETWORK

VOUT

RESISTOR

STRING DAC

POWER-DOWN

CIRCUITRY

AMPLIFIER

DB15 DB14 DB13 DB12 DB11 DB10

DB9

DB8

DB7

DB6

DB5

DB4

DB3

DB2

DB1

DB0

PD1

PD0

DAC D DAC C DAC B DAC A

COMMAND

DAC ADDRESS

(DON’T CARE)

DON’T CARE

POWER-

DOWN MODE

DAC SELECT

(1 = DAC SELECTED)

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