AD5683RARMZ datasheet(23/28 Pages) AD

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Data Sheet

AD5683R/AD5682R/AD5681R/AD5683

Rev. D | Page 23 of 28

INTERNAL REGISTERS

Input Shift Register

The shift register of the AD5683R/AD5682R/AD5681R/AD5683

is 24 bits wide. Serial data is loaded MSB first (DB23) and the

first four bits are the command bits, C3 to C0, followed by the

data bits.

The data bits comprise a 20-bit, 18-bit, or 16-bit input code,

followed by a number of don’t care bits as shown in Table 9.

The command is decoded on the rising edge of SYNC.

Input Register

The input register acts as a buffer to preload new data. This

two different ways to transfer the contents of the input register

to the DAC register: by software or by hardware.

DAC Register

The DAC register controls the voltage in the VOUT pin. This

transferring the contents of the input register to the DAC

COMMANDS

Write Input Register

The input register allows the preloading of a new value for the

DAC register. The transfer from the input register to the DAC

software using Command 2.

If new data is loaded into the DAC register directly using

Command 3, the DAC register automatically overwrites the

input register.

Update DAC Register

This command transfers the contents of the input register to the

DAC register and, consequently, the VOUT pin is updated.

This operation is equivalent to a software LDAC.

Write DAC Register

The DAC register controls the output voltage in the DAC. This

command updates the DAC register on completion of the write

operation. The input register is refreshed automatically with the

DAC register value.

Table 9. Command Operation

Command

[DB23:DB20]

Data Bits [DB19:DB0]1

Operation

DB19 DB18 DB17 DB16 DB15

DB14

[DB13:DB8] DB7

DB6

DB5

DB4

[DB3:DB0]

X…X

Do nothing

DB15

DB14

DB13 DB12

DB11

DB10

DB9…DB4

DB32

DB22 DB12,3

DB02,3 X…X

Write input register

X…X

Update DAC register

(software LDAC)

DB15

DB14

DB13 DB12

DB11

DB10

DB9…DB4

DB32

DB22 DB12,3

DB02,3 X…X

Write DAC and input

DB19

DB18

DB17 DB16

DB15

DB14

0…0

Write control register

X…X

Readback input

X means don’t care.

This bit is a don’t care bit for the AD5681R only.

This bit is a don’t care bit for the AD5682R only.

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