AN-1198: Software Configurable, 12-Bit Dual-Channel, Unipolar/Bipolar Voltage Output Using the AD5722R DAC

Circuit Function Benefits

This circuit provides unipolar and bipolar data conversion using the AD5722R, a dual, 12-bit, serial input, unipolar/bipolar voltage output DAC. The only external components needed for this 12-bit DAC 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

The AD5722R is a digital-to-analog converter (DAC) that offers guaranteed 12-bit monotonicity, integral nonlinearity (INL) of ±0.5 LSB, 0.1% total unadjusted error (TUE), and 10 µs settling time. The AD5722R also integrates a 2.5 V, 5 ppm/°C voltage reference, 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 and AVSS supply range from −4.5 V to −16.5 V. AVSS can be connected to 0 V if only unipolar outputs are required. The output range can be individually programmed for each output channel 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 0.07 %FSR.

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).

Figure 1. Unipolar/Bipolar Configuration for the AD5722R DAC.