Datasheet

_________________________________________________________________ Maxim Integrated Products 7
Evaluates: MAX5723/MAX5724/
MAX5725A/MAX5725B
MAX5725A Evaluation Kit
Detailed Description of Software
The MAX5725A EV kit software can evaluate the SPI
interface MAX5725A family of 12-/10-/8-bit DACs. The
main software window has three tabs: DACs, Scripts,
and Configuration Status. Within the DACs tab sheet
(Figure 2), the user can set the reference and DAC
outputs. The Scripts tab sheet (Figure 3) allows the
user to send a sequence of write commands to the
eight DACs, and load and save the write sequence. The
Configuration Status tab sheet (Figure 4) displays the
configuration settings for each DAC. In addition, the soft-
ware allows the user to adjust the configuration, power,
reset, and default settings.
Demo Mode
The EV kit software enters the demo mode when the USB
connection is not detected. When in demo mode, all
communication to the EV kit is disabled; however, most
of the software is functional. Demo mode allows the user
to evaluate the software without hardware connectivity.
Part Selection
The user must select the appropriate radio button in
the Part Selection group box that corresponds to the
installed Maxim IC DAC bits.
SPI Interface
When the software first starts up, the SPI radio button
is selected automatically. If the user selects the I2C
radio button, then the software searches for a valid I
2
C
address that is on the bus. If no address is found, the
software returns to the SPI radio button selection.
The EV kit is capable of evaluating I
2
C parts by replac-
ing U1. Once the I
2
C part is installed, refer to the I
2
C
Address section in the MAX5825A EV kit data sheet.
Reference
The reference default configuration is set to 2.5V using
the external voltage reference IC (U7). The external 2.5V
reference can be connected between the EXT_REF pin
and its corresponding ground. Select the External Ref
radio button and type the reference voltage into the
edit box. Removing the shunt from jumper JU11 allows
internal reference options that include 2.048V, 2.5V, and
4.096V selection using the corresponding radio buttons.
Make sure the VDD supply is greater or equal to the volt-
age reference selected for proper operation. When the
EV kit uses the on-board 3.3V supply to power the IC, the
4.096V radio button selection will not provide the 4.096V.
DAC Commands
Within the DACs tab sheet (Figure 2), the user can set
the output of the DACs with two options. The first option
is the Quick DAC Output Voltage group box that allows
the user to write and load the CODE to all the DACs. Set
the desired output for each DAC using the correspond-
ing slider and press the EXECUTE button. The second
option is to write the return CODE, write the CODE, load
the CODE, or write and load the CODE to the desired
DAC using the drop-down lists and edit box within the
Command group box. Press the EXECUTE button once
all the settings are appropriately configured.
DAC Commands (Script)
Within the Scripts tab sheet (Figure 3), enter the desired
Data on the left and choose the appropriate Command
from the drop-down list. Pressing the EXECUTE button
writes to the CODE and/or DAC registers and the Script
Status changes from Incomplete to Complete. Refer
to the MAX5725A IC data sheet for a list of possible
commands. If a sequence of commands needs to be
performed, adjust all Data edit boxes and Command
drop-down lists accordingly, and press the EXECUTE
ALL button. To reset the Script Status to Incomplete,
press the RESET SCRIPT button.
Data Logging
Using the SAVE button, the sequence of commands can
be saved into a text file format. To recall the sequence,
press the LOAD button and select the appropriate text file.
Configuration Status
The Configuration Status tab sheet (Figure 4) displays
the current status of the configuration, power, and default
settings for each DAC.
Read Back
The EV kit reads back the return, CODE, DAC, and
watchdog values. Check the INC checkbox to increment
the address pointer and select the appropriate radio
button to set the DOUT PHASE equal to 0 or 1 when
reading back. Select the appropriate Read radio button
and press the EXECUTE button in the Read Back group
box.
Asynchronous CLR
A checked CLR Asserted checkbox drives the CLR pin
of the IC low, which clears the content of both CODE and
DAC registers. Unchecking the CLR Asserted checkbox
drives the CLR pin high and writing new commands is
allowed again.
Asynchronous LDAC
A checked LDAC Asserted checkbox drives the LDAC
pin of the IC low, which allows writing to the CODE
register and then automatically transfers to the DAC
register to change the DAC’s output. Unchecking the
LDAC Asserted checkbox drives the LDAC pin high.
To change the DAC outputs, the user must write to the
CODE registers, and then write to the DAC registers.