AD5665RBCPZ-R2 datasheet(31/36 Pages) AD

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Data Sheet

AD5625R/AD5645R/AD5665R, AD5625/AD5665

Rev. C | Page 31 of 36

POWER-ON RESET AND SOFTWARE RESET

The AD56x5R/AD56x5 contain a power-on reset circuit that

controls the output voltage during power-up. The 10-lead

version of the device powers up to 0 V. The 14-lead version has

a power-on reset (POR) pin that allows the output voltage to

be selected. By connecting the POR pin to GND, the AD56x5R/

AD56x5 output powers up to 0 V; by connecting the POR pin to

VDD, the AD56x5R/AD56x5 output powers up to midscale. The

output remains powered up at this level until a valid write sequence

is made to the DAC. This is useful in applications where it is

important to know the state of the output of the DAC while it is

in the process of powering up.

Any events on LDAC or CLR during power-on reset are ignored.

There is also a software reset function. Command 101 is the

software reset command. The software reset command contains

two reset modes that are software programmable by setting bit

DB0 in the input shift register.

Table 16 shows how the state of the bit corresponds to the

software reset modes of operation of the devices. Figure 71

shows the contents of the input shift register during the

software reset mode of operation.

Table 16. Software Reset Modes for the AD56x5R/AD56x5

DB0

Registers Reset to Zero

DAC register

Input shift register

1 (Power-On Reset)

DAC register

Input shift register

LDAC register

Power-down register

Internal reference setup register

INTERNAL REFERENCE SETUP (R VERSIONS)

The on-chip reference is off at power-up by default. It can be

turned on by sending the reference setup command (111) and

setting DB0 in the input shift register. Table 17 shows how the

state of the bit corresponds to the mode of operation.

Table 17. Reference Setup Command

DB0

Action

Internal reference off (default)

Internal reference on

Figure 71. Reset Command

Figure 72. Reference Setup Command

DB15 DB14 DB13 DB12 DB11 DB10

DB9

DB8

DB7

DB6

DB5

DB4

DB3

DB2

DB1

DB0

RST

COMMAND

DAC ADDRESS

(DON’T CARE)

DON’T CARE

DB15 DB14 DB13 DB12 DB11 DB10

DB9

DB8

DB7

DB6

DB5

DB4

DB3

DB2

DB1

DB0

REF

COMMAND

DAC ADDRESS

(DON’T CARE)

DON’T CARE

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