D/A Converter

What is a D/A Converter?

A D/A (Digital-to-Analog) converter is a circuit that transforms digital signals into analog. It is commonly used in applications where an MCU needs to provide analog control, such as driving speakers or provide a reference voltage for other components.

Digital signals consist of only 0s and 1s, whereas analog signals can take on an infinite range of values. Therefore, when converting digital signals to analog, two important factors must be considered: 1) the reference voltage that defines the range of the output analog signal, and 2) the resolution that determines the number of divisions used for conversion.
The reference voltage consists of a positive reference voltage (+VREF) and negative reference voltage (-VREF) that determine the output range of the D/A converter. In many MCUs with built-in D/A converters, -VREF is typically set to of 0V, resulting in an output from 0 to VREF.
Resolution defines how precisely (smoothly), the D/A converter can reproduce an analog signal. A 10-bit resolution, for example, allows the output to be divided into 210=1024 discrete levels within the VREF range. Here, the smallest step size, calculated as VREF/1024, is known as 1LSB (Least Significant Bit).

Resolution can be 8-bit, 10-bit, 12-bit, 16-bit, and so on, with higher values allowing for smoother reproduction of the analog signal. Conversely, lower resolution results in a more step-like, or jagged analog output. The resolution is determined by the number of digital input signals. For instance, in an 8-bit D/A converter, there are 8 digital inputs, and the VREF voltage is divided into 28=256 discrete levels.