Datasheet

Data Sheet AD5751
Rev. B | Page 21 of 32
THEORY OF OPERATION
The AD5751 is a single-channel, low cost, precision, voltage/
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 AD5751 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/voltage range.
The output current range is programmable across three ranges:
0 mA to 20 mA, 0 mA to 24 mA, or 4 mA to 20 mA. The voltage
output is provided from a separate pin that can be configured to
provide 0 V to 5 V, 0 V to 10 V, and 0 V to 40 V output ranges.
An overrange of 20% is available on the 5 V and 10 V output
voltage ranges, and of 10% on the 0 V to 40 V range. The VOUT
and IOUT pins can be connected together. An overrange of 2%
is available on the 0 mA to 20 mA, 0 mA to 24 mA, and 4 mA to
20 mA current ranges. The current and voltage outputs are
available on separate pins. Only one output can be enabled at
one time. The output range is selected by programming the R3
to R0 bits in the control register (see Table 7 and Table 8).
Figure 50 and Figure 51 show a typical configuration of AD5751 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 AD5751 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 AD5751, can be supplied from a
reference such as the ADR392. The AD5751 can operate with a
single supply up to 55 V.
SOFTWARE MODE
In current mode, software-selectable output ranges include 0 mA
to 20 mA, 0 mA to 24 mA, or 4 mA to 20 mA.
In voltage mode, software-selectable output ranges include 0 V
to 5 V, 0 V to 10 V, 0 V to 40 V.
07269-006
VSENSE+
VIN
SCLK
VDD
REFIN
SDI/DIN
SDO
SYNC1
SYNC
SDO
SDIN
SCLK
AD506x
AD566x
MCU
VOUT
0V TO 5V, 0V TO 10V,
0V TO 40V
IOUT
0mA TO 20mA,
0mA TO 24mA,
4mA TO 20mA
VOUT
RANGE
SCALE
IOUT
RANGE
SCALE
VOUT SHORT FAULT
IOUT OPEN FAULT
OVERTEMP FAULT
STATUS REGISTER
SERIAL
INTERFACE
VREF
HW SELECT
FAULT
ADP1720
ADR392
AVDD AGND
AVDD GND
AD5751
Figure 50. Typical System Configuration in Software Mode (Pull-Up Resistors Not Shown for Open-Drain Outputs)