Analog Devices EV-AD74412RSDZ, Руководство пользователя

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UG-1634 EV-AD74412RSDZ User Guide
Rev. 0 | Page 8 of 15
EXAMPLE SEQUENCE
This section demonstrates how to configure the AD74412R for
a selected function. The AD74412R data sheet must be consulted
when programming the device.
Force Voltage Measure Current Example
This example is used to configure the AD74412R in voltage
output mode, sourcing 11 V across the Channel A screw terminals.
This example also measures the corresponding current through
the R
SENSE
resistor using the on-chip, analog-to-digital converter
(ADC). The ADC measurement is completed using a conversion
rate of 20 SPS with 50 Hz and 60 Hz rejection enabled. See Table 2
for the full list of commands.
A suitable load must be placed across the screw terminals. Refer
to the
AD74412R data sheet for more information.
To complete the register write steps shown in Table 2 using the
AD74412R GUI, take the following steps:
1. In the Configure tab, use the dropdown menus to select
Actuators and Voltage Output (see Figure 4 ) .
2. In the Advanced Settings panel, set the DAC Code slider
to 8191 (11 V).
3. Click
Apply
. This executes all writes required to configure
the device and to enable ADC conversions in the default
mode. This configuration allows the
AD74412R to measure
voltage across the R
SENSE
resistor in the 0 V to 2.5 V range at
a 20 SPS conversion rate.
4. Click the
View Results
tab to view the ADC results.
See Figure 10 for the corresponding script.
Table 2. Force Voltage Measure Current Instruction Set
Instruction Instruction Description W/R 1
Register Name
and Address
Data Notes
1 Configure Channel A in
voltage output mode
W CH_FUNC_SETUPA,
Address 0x01
0x0001
2 Write full-scale code to
DAC_A to generate 11 V W DAC_CODEA,
Address 0x16
0x1FFFF LDAC pin voltage = 0 V to allow outputs to be updated instantly.
3 Measure 11 V across
Channel A screw terminals N/A
2
N/A
2
N/A
2
Use handheld meter to verify voltage.
4 Enable ADC to convert and
measure current through
R
SENSE
resistor
W ADC_CONV_CTRL,
Address 0x23
0x0201 When the write in Instruction 1 is executed, the ADC automatically
configures to measure voltage across the R
SENSE
resistor in a 0 V to
2.5 V range.
5 Read ADC results R ADC_RESULTA,
Address 0x26
6 Calculate current through
R
SENSE
resistor using the
equation available in the
AD74412R data sheet
N/A
2
N/A
2
N/A
2
_
65535
 
 
 
 
   
 
 
 
 

MIN
RSENSE
SENSE
AD CODE
V Voltage Range
I
R
where:
I
RSENSE
is the current through the R
SENSE
resistor.
V
MIN
is −2.5 V, the minimum voltage is in the −2.5 V to 2.5 V range.
The voltage range is 5 V.
7 Stop ADC conversions W ADC_CONV_CTRL,
Address 0x23 0x0000
8 Program DAC_A to zero scale W DAC_CODEA,
Address 0x16 0x0000 Cleanup of DAC code and channel configuration is recommended
before reprogramming the device.
9 Reset Channel A to
high-Z mode W CH_FUNC_SETUPA,
Address 0x01
0x0000
1 W is write and R is read.
2 N/A is not applicable.