AN-1195: Software Configurable 12-Bit Quad-Channel Unipolar/Bipolar Voltage Output Using the AD5724 DAC

Circuit Function and Benefits

This circuit provides unipolar and bipolar data conversion using the AD5724BREZ, a quad, 12-bit, serial input, unipolar/bipolar voltage output DAC and the REF192ESZ precision 2.5 V voltage reference. The only other external components needed for this 12-bit DAC circuit are decoupling capacitors on the supply pins and reference input, leading to savings in cost and board space. This circuit is well suited for closed-loop servo control applications.

Circuit Description

Table 1. Devices Connected/Referenced
Product	Description
AD5724	Complete, quad, 12-bit, serial input, unipolar/bipolar voltage output DAC
REF192	Precision 2.5 V voltage reference

The AD5724 is a digital-to-analog converter (DAC) that offers guaranteed 12-bit monotonicity, integral nonlinearity (INL) of ±1 LSB, 0.1% total unadjusted error (TUE), and 10 µs settling time. The AD5724 also integrates reference buffers and output amplifiers. This leads to further savings in both cost and board space. Performance is guaranteed over the following supply voltage ranges:

AVDD supply range from +4.5 V to +16.5 V.
AVSS supply range from −4.5 V to −16.5 V. AVSS can be connected to 0 V if only unipolar outputs are required.

Figure 1. Unipolar/Bipolar Configuration for the AD5724 DAC (Simplified Schematic).

The output range can be individually programmed for each of the four outputs with these options: 0 V to +5 V, 0 V to +10 V, 0 V to +10.8 V, −5 V to +5 V, −10 V to +10 V, and −10.8 V to +10.8 V. The input coding is user selectable twos complement or offset binary for a bipolar output (depending on the state of the BIN/2sCOMP pin). Coding is straight binary for a unipolar output. Figure 2 shows that the typical output error of this circuit at 25°C ambient temperature is less than 0.06 %FSR.

Figure 2. Voltage Output Error.

The circuit must be constructed on a multilayer printed circuit board (PCB) with a large area ground plane. Proper layout, grounding, and decoupling techniques must be used to achieve optimum performance (see MT-031 Tutorial, Grounding Data Converters and Solving the Mystery of AGND and DGND and MT-101 Tutorial, Decoupling Techniques).