AD5666

Rev. A | Page 24 of 28

Table 9. Daisy-Chain Enable/Internal Reference Register

DCEN (DB1)

REF (DB0)

Action

0

0

Standalone mode, reference off (default)

0

1

Standalone mode, reference on

1

0

DCEN mode, reference off

1

1

DCEN mode, reference on

Table 10. 32-Bit Input Shift Register Contents for Daisy-Chain Enable and Reference Set-Up Function

MSB

LSB

DB31 to DB28

DB27

DB26

DB25

DB24

DB23

DB22

DB21

DB20

DB19 to DB2

DB1

DB0

X

1

0

0

0

X

X

X

X

X

1/0

1/0

Don’t cares

Command bits (C3 to C0)

Address bits (A3 to A0)

Don’t cares

DCEN/REF

register

Table 11. Modes of Operation

DB9

DB8

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

Table 12. 32-Bit Input Shift Register Contents for Power-Up/Power-Down Function

MSB

LSB

DB31 to

DB28

DB27

DB26

DB25

DB24

DB23

DB22

DB21

DB20

DB19 to

DB10

DB9

DB8

DB7 to

DB4

DB3

DB2

DB1

DB0

X

0

1

0

0

X

X

X

X

X

PD1

PD0

X

DAC D

DAC C

DAC B

DAC A

Don’t

cares

Command bits (C2 to C0)

Address bits (A3 to A0)—

don’t cares

Don’t

cares

Power-down

mode

Don’t

cares

Power-down/power-up channel selection—

set bit to 1 to select

RESISTOR

NETWORK

RESISTOR

STRING DAC

POWER-DOWN

CIRCUITRY

AMPLIFIER

Figure 44. Output Stage During Power-Down