AD5686 datasheet(19/28 Pages) AD

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Data Sheet

AD5686/AD5684

Rev. A | Page 19 of 28

SERIAL INTERFACE

The AD5686/AD5684 have a 3-wire serial interface (SYNC,

SCLK, and SDIN) that is compatible with SPI, QSPI™, and

MICROWIRE® interface standards as well as most DSPs. See

Figure 2 for a timing diagram of a typical write sequence. The

AD5686/AD5684 contain an SDO pin to allow the user to daisy-

chain multiple devices together (see the Daisy-Chain Operation

section) or for readback.

Input Shift Register

The input shift register of the AD5686/AD5684 is 24 bits wide.

Data is loaded MSB first (DB23). The first four bits are the

command bits, C3 to C0 (see Table 8), followed by the 4-bit

DAC address bits, DAC A, DAC B, DAC C, andDAC D (see

Table 9), and finally the bit data-word.

For the AD5686, the data-word comprises 16-bit input code(see

Figure 38). For the AD5684, the data-word comprises 12-bit input

code, followed by zero or four don’t care bits (see Figure 39).

These data bits are transferred to the input register on the 24

falling edges of SCLK and are updated on the rising edge

of SYNC.

Commands can be executed on individual DAC channels,

combined DAC channels, or on all DACs, depending on the

address bits selected (see Table 9).

Table 8. Command Bit Definitions

Command Bits

Description

No operation

Write to Input Register n (dependent on LDAC)

Update DAC Register n with contents of Input

Write to and update DAC Channel n

Power down/power up DAC

Hardware LDAC mask register

Software reset (power-on reset)

Reserved

Set up DCEN register (daisy-chain enable)

Set up readback register (readback enable)

Reserved

…

Reserved

Table 9. Address Bits and Selected DACs

Address Bits

Selected DAC Channel1

DAC D

DAC C

DAC B

DAC A

DAC B

DAC C

DAC D

DAC A and DAC B

All DACs

Any combination of DAC channels can be selected using the address bits.

Figure 38. AD5686 Input Shift Register Contents

Figure 39. AD5684 Input Shift Register Contents

ADDRESS BITS

COMMAND BITS

DAC

D15 D14 D13 D12 D11 D10

DB23 (MSB)

DB0 (LSB)

DATA BITS

ADDRESS BITS

COMMAND BITS

DAC

D11 D10

DB23 (MSB)

DB0 (LSB)

DATA BITS

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