Application of 3V DAC in ±10V

Overview

Modern logic systems powered by 3.3V power supplies sometimes run in industrial environments and may require ±10V voltage drives, such as PLCs , transmitters, motor controls, etc. One way to meet this need is to choose a DAC that can provide a voltage swing of ±10V, but a better approach is to use a 3.3V DAC and then amplify its output to ±10V for the following reasons:

• 3.3V DACs have higher logic integrity than ±10V DACs.

• The 3.3V DAC has a higher-speed logic interface, which can free up some tasks from the microcontroller to handle other tasks.

• The DAC may be integrated into a large-scale, 3.3V powered chip (such as a microcontroller) and cannot provide a ±10V output swing.

• The external load may require a certain output current drive, or drive a capacitive load, and a ±10V DAC cannot meet this requirement.

Circuit diagram

The circuit block diagram is shown in Figure 1a (see the Details tab) and contains five main parts: DAC , reference source, bias adjustment, reference source buffer and output buffer.

The DAC provides digital-to-voltage conversion relative to a reference point voltage. The bias circuit adjusts the DAC's unipolar transfer function to produce a bipolar output and calibrates the 0V output point. The reference buffer provides load isolation and offset regulation for the reference source. The output buffer adds the bias voltage to the signal and provides the required gain so that the output swings to the desired level. In addition, the output buffer also provides certain load driving capabilities.