AD5749
THEORY OF OPERATION
The AD5749 is a single-channel, low cost, precision, current
output driver with hardware or software programmable output
ranges. The software ranges are configured via an SPI-/
MICROWIRE-compatible serial interface. The hardware ranges
are programmed using the range pins (R0 to R3). The analog
input to the AD5749 is provided from a low voltage, single-supply
DAC (0 V to 4.096 V), which is internally conditioned to provide
the desired output current range.
The output current range is programmable across two ranges:
0 mA to 24 mA, or 4 mA to 20 mA. An overrange of 2% is
available on the 0 mA to 24 mA and 4 mA to 20 mA current
ranges. The output range is selected by programming the R3
to R0 bits in the control register (see Table 7 and Table 8).
Figure 31 and Figure 32 show a typical configuration of AD5749 in
software mode and in hardware mode, respectively, in an output
module system. The HW SELECT pin chooses whether the part
is configured in software or hardware mode. The analog input to
the AD5749 is provided from a low voltage, single-supply DAC
such as the AD506x or AD566x, which can provide an output
range of 0 V to 4.096 V. The supply and reference for the DAC,
as well as the reference for the AD5749, can be supplied from a
reference such as the ADR392. The AD5749 can operate with a
single supply up to 55 V.
SOFTWARE MODE
The software-selectable output ranges are 0 mA to 24 mA, or
4 mA to 20 mA.
AVDD AGND
MCU
ADP1720
ADR392
VDD REFIN
SCLK
SDI/DIN
SDO
SYNC1
AD506x
AD566x
VREF
VIN
AVDD GND
AD5749
IOUT
RANGE
SCALE
IOUT
0mA TO 20mA,
0mA TO 24mA,
4mA TO 20mA
SCLK
SDIN
SDO
SYNC
SERIAL
INTERFACE
IOUT OPEN FAULT
OVERTEMP FAULT
STATUS REGISTER
HW SELECT
FAULT
Figure 31. Typical System Configuration in Software Mode (Pull-Up Resistors Not Shown for Open-Drain Outputs)
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