AD5752 datasheet(29/32 Pages) AD

29 / 32 page

AD5722/AD5732/AD5752

Rev. 0 | Page 29 of 32

long-term drift specification ensures that the overall

solution remains relatively stable over its entire lifetime.

•

Reference output voltage noise needs to be considered in

high accuracy applications that have relatively low noise

budgets. It is important to choose a reference with as low

an output noise voltage as practical for the required system

resolution. Precision voltage references such as the ADR431

(XFET® design) produce low output noise in the 0.1 Hz to

10 Hz range. However, as the circuit bandwidth increases,

filtering the output of the reference may be required to

minimize the output noise.

MICROPROCESSOR INTERFACING

Microprocessor interfacing to the AD5722/AD5732/AD5752 is

via a serial bus that uses a standard protocol compatible with

microcontrollers and DSP processors. The communications

channel is a 3-wire (minimum) interface consisting of a clock

signal, a data signal, and a synchronization signal. The AD5722/

AD5732/AD5752 require a 24-bit data-word with data valid on

the falling edge of SCLK.

For all interfaces, the DAC output update can be initiated

automatically when all the data is clocked in, or it can be

performed under the control of LDAC

AD5722/AD5732/AD5752 to Blackfin® DSP Interface

. The contents of the

registers can be read using the readback function.

Figure 44 shows how the AD5722/AD5732/AD5752 can be

interfaced to the Analog Devices Blackfin DSP. The Blackfin has

an integrated SPI port that can be connected directly to the SPI

pins of the AD5722/AD5732/AD5752 and the programmable I/O

pins that can be used to set the state of a digital input such as

the LDAC

SYNC

ADSP-BF531

AD5722/

AD5732/

AD5752

SCLK

SDIN

SPISELx

SCK

MOSI

LDAC

PF10

pin.

Figure 44. AD5722/AD5732/AD5752 to Blackfin Interface

Table 28. Some Precision References Recommended for Use with the AD5722/AD5732/AD5752

Part No.

Initial Accuracy (mV max)

Long-Term Drift (ppm typ)

Temp Drift (ppm/°C max)

0.1 Hz to 10 Hz Noise (µV p-p typ)

ADR431

±1

3.5

ADR421

±1

1.75

ADR03

±2.5

ADR291

±2

AD780

±1

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