AD5753 datasheet(40/72 Pages) AD

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AD5753

Data Sheet

Rev. 0 | Page 40 of 72

The decimal value that is written to the internal DAC register

(DAC code) is calculated with the following equation:

(

DAC code

= ×

+−

where:

D is the code loaded to the DAC_INPUT register.

M is the code in the USER_GAIN register (default code = 216 − 1).

C is the code in the USER_OFFSET register (default code = 215).

Data from the DAC_INPUT register is processed by a digital

multiplier and adder and both are controlled by the contents of

the user gain and user offset registers, respectively. The calibrated

DAC data is then loaded to the DAC. The loading of the DAC data

is dependent on the state of the LDAC pin.

Each time data is written to the USER_GAIN or USER_

OFFSET register, the DAC output is not automatically updated.

Instead, the next write to the DAC_INPUT register uses these

user gain and user offset values to perform a new calibration

and to automatically update the output channel. The read only

DAC_OUTPUT register represents the value currently available at

the DAC output, except in the case of user gain and user offset

calibration. In this case, the DAC_OUTPUT register contains

the DAC data input by the user, on which the calibration is

performed and not the result of the calibration.

Both the USER_GAIN register and the USER_OFFSET register

have 16 bits of resolution. The correct method to calibrate the

gain and offset is to first calibrate the gain and then calibrate the

offset.

DAC OUTPUT UPDATE AND DATA INTEGRITY

DIAGNOSTICS

Figure 83 shows a simplified version of the DAC input loading

circuitry. If used, the USER_GAIN and USER_OFFSET registers

must be updated before writing to the DAC_INPUT register.

VIOUT

INTERFACE LOGIC

OUTPUT

AMPLIFIER

SDO

SDI

16-BIT

DAC

REFIN

SYNC

LDAC

(HARDWARE OR SOFTWARE)

DAC INPUT

USER

GAIN AND OFFSET

CALIBRATION

SCLK

DAC OUTPUT

(READ ONLY)

CLEAR CODE

CLEAR EVENT

(WDT TIMEOUT)

Figure 83. Simplified Serial Interface of Input Loading Circuitry

AD5753 Datasheet(PDF) 40 Page - Analog Devices

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