Data Sheet

AD5751

Rev. D | 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.

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)