AD5737 datasheet(16/31 Pages) AD

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AD5757/AD5737

Preliminary Technical Data

Rev. PrD | Page 16 of 31

PROGRAMMING SEQUENCE TO WRITE/ENABLE

THE OUTPUT CORRECTLY

To correctly write to and set up the part from a power on

condition the sequence below should be followed. It is

recommended to perform a hardware or software reset after

initial power on.

Firstly, the DC-DC supply block needs to be configured. The

user should set the DC-DC switching frequency, max output

voltage allowed and the phase that the 4 DC-DC channels clock

at. Secondly the DAC Control Register should be configured on

a per channel basis. The output range is selected, and the DC-

DC block is enabled (DC-DC). Other control bits may be

configured at this point, however, the output enable bit

(OUTEN) and the INT_ENABLE bit should not be set. Next,

the user writes the required code to the DAC Data Register.

This will implement a full DAC calibration internally. Finally

the user writes to the DAC Control Register again to enable the

output (set the OUTEN bit). A flow chart of this sequence is

shown below.

Figure 16. Programming Sequence for Enabling the Output Correctly

CHANGING AND REPROGRAMMING THE RANGE

When changing between ranges the same sequence as above

should be used. It is recommended to set the range to its zero

point (can be mid-scale or zeroscale) prior to disabling the

output. As the DC-DC switching frequency, max voltage and

phase have already been selected, there is no need to reprogram

this. A flow chart of this sequence is shown below.

Figure 17. Steps for Changing the Output Range

Power On

Step 2: Write to DC-DC Control Register to

set DC-DC Clock Frequency, phase

and maximum voltage.

Step 3:Write to DAC Control Register. Select

the DAC Channel and output Range.

Set the DC_DC bit and other control

bits as required. Do not select OUTEN

bit or the INT_ENABLE bit..

Step 4:Write to each/all DAC Data Registers.

Step 5:Write to DAC Control Register. Reload

sequence as in Step 3 above.This time

select the OUTEN bit to enable the

output.

Step 1: Perform a Software/Hardware Reset

Step 1: Write to channels DAC Data Register,

Set the output to 0V (zero or mid-

scale).

Step 2:Write to DAC Control Register. Disable

the output (OUTEN=0), and set the

new output range. Keep the DC-DC

enabled, do not select the

INT_Enable bit.

Step 3:Write value to the DAC Data Register.

Step 4:Write to DAC Control Register. Reload

sequence as in Step 2 above.This time

select the OUTEN bit to enable the

output.

Channels Output is enabled

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