Comprehensive Introduction: What Is DAC-Digital Analogue Converter

DAC(Digital Analogue Converter) is like a powerful translator, building a bridge between digital signals and analog signals, which are two very different "languages", so that we can enjoy wonderful music, clear images with the help of DAC digital analogue converter.

Working principle of DAC digital analogue converter

Before discussing the working principle of DAC digital analogue converter, first, let's look at what digital signals and analog signals are. A digital signal is made up of a series of discrete numerical values, like a string of numbers encoded in a particular code, usually denoting information as 0 and 1. An analog signal is a continuously changing signal, such as the sound we hear, which changes continuously in time and amplitude. An analog signal is a continuously changing physical quantity, such as voltage or current. DAC digital analogue converter is the converter between these two signals, which can convert digital signals to analog signals, so as to achieve data interaction between digital and analog systems.

When a digital signal is fed into a DAC digital analogue converter, it is firstly stored in a digital register. Then, according to the instructions of the digital signal, the analog electronic switch controls the output of the analog signal.

Performance index of DAC digital analogue converter

The performance index of DAC digital analogue converter can be concluded in six factors, with which you can quickly measure the quality of your DAC digital analogue converter.

Resolution

Resolution is the precision of the analog output that a DAC digital analogue converter can produce, usually expressed in bits, which reflects the minimum change in the output analog.

The resolution of the DAC digital analogue converter has a definite relationship with the number of bits of the input digit quantity. The more bits, the higher the resolution, and the finer the analog output value that the DAC digital analogue converter can distinguish.

Conversion speed

The conversion speed represents how many signal conversions the DAC digital analogue converter can complete per second, i.e. the conversion frequency.

The conversion frequency depends on the DAC digital analogue converter's internal clock frequency and conversion method. Common conversion methods of DAC digital analogue converter include serial DAC and parallel DAC. Serial DAC is converted bit by bit, the conversion frequency is low; While parallel DAC converts all bits at the same time, the conversion frequency is higher. In addition, the conversion speed of DAC digital analogue converters is also affected by circuit design, power consumption and anti-interference performance.

Setup time

The setup time refers to the time that the output analog stabilizes to the corresponding numerical range (stable value ±LSB) after the input digital quantity changes.

Setup time is a dynamic index of D/A conversion rate. The length of the actual establishment time is not only related to the conversion rate of the DAC digital analogue converter itself, but also to the size of the digital quantity change. When the input number changes from all 0 to all 1 (or from all 1 to all 0), the setup time is the longest, and the setup time is called the full scale change time.

Linearity

Linearity is the maximum deviation between the actual transformation characteristic curve and the ideal linear characteristic, often expressed as a percentage relative to the full scale.

Ideally, the conversion curve of the DAC digital analogue converter should be a straight line, but in practice, due to various factors, the conversion curve will have a certain deviation. The smaller the nonlinear error, the better the linearity of the DAC digital analogue converter, and the higher the accuracy of the output analog signal.

Absolute accuracy/ accuracy

Absolute accuracy refers to the maximum error between the actual output value and the theoretical value of the analog quantity corresponding to any input digit in the whole scale range.

Absolute accuracy is an important index to measure the accuracy of output analog signal. It is mainly caused by the gain error, zero error, nonlinear error and differential nonlinear error of DAC digital analogue converters. Generally, it should be less than 1 LSB. The higher the absolute accuracy, the closer the DAC digital analogue converter's output analog signal is to the theoretical value.

Relative accuracy

Relative accuracy is similar to absolute accuracy, except that the maximum deviation is expressed as a percentage of the full-scale analog voltage, or the corresponding digital quantity is expressed as a binary fraction.

Relative accuracy provides another way to measure the accuracy of a DAC digital analogue converter 's output analog signal. Compared with absolute accuracy, relative accuracy pays more attention to the ratio of error to full-scale analog voltage.

Different types of DAC digital analogue converter

There are many types of DAC digital analogue converters in the electronic fields, and in this section, let us have a look at the three major types that are frequently applied in our daily life.

 

Three main types of DAC digital analogue converter
R-2R DAC	Use R-2R networks to convert digital signals to analog signals.
	The R-2R network consists of a series of resistors and switches, each connected to a resistor, forming a voltage divider circuit.
	The digital input signals control the on-off of these switches, so that different combinations of resistors are selected to produce output voltages of different amplitude.
Serial DAC	The serial DAC transmits data based on the serial interface, and the digital input signal is input to the DAC bit by bit in serial mode.
	The internal contains a shift register and a DAC core circuit. The shift register is used to receive and store the serial input digital signal, and the DAC core circuit generates the corresponding analog output according to the stored digital signal.
Parallel DAC	Parallel DAC represents the analog value to be output through multiple parallel input bits, each of which is directly connected to a switch or resistor network inside the DAC.
	Digital input signals are fed into all input bits simultaneously, and the DAC simultaneously selects different resistance combinations or switching states based on these input signals to produce the corresponding analog output.

Characteristics and advantages of DAC digital analogue converter

After understanding the basic principles and the major types of DAC digital analogue converter, we come to look at the characteristics and unique advantages of DAC digital analogue converter.

As what we have mentioned in the previous section, R-2R DAC has a simpler structure compared to other converters. And it has higher accuracy because the voltage division characteristic of the R-2R network makes a good linear relationship between the output and the input digital quantity. Therefore, this type of DAC digital analogue converter is suitable for applications requiring high precision and resolution.

As for serial DAC, it is easy to achieve high-speed data transmission because the serial interface can reduce the number of pins required for data transmission, thus increasing the data transmission speed. Compared with parallel DAC, serial DAC have fewer pins, which is conducive to reducing the size of the board and reducing the cost. Thus, serial DAC is suitable for applications requiring high-speed data transmission and control, such as communication systems and digital audio processing.

And for parallel DAC, its conversion speed is relatively slow because multiple input bits need to be processed simultaneously. However, it still has some advantages in applications that require higher resolution, because parallel inputs can provide more bits to represent the analog output. The circuit structure of parallel DAC is relatively complex, but the output stability is better, which makes it suitable to meet the requirements of high accuracy and stability of analog output.

Wide application of DAC digital analogue converter

The application of DAC digital analogue converter is broad, the following introduced are the three most important areas of DAC.

Firstly, DAC digital analogue converter plays a crucial role in audio and video processing. It converts audio data and digital video signals (such as MP3, TV monitors, etc.) stored in digital formats into analog audio signals or analog video signals, and then plays audio and video signals acceptable to humans through speakers or display screens. This conversion ensures that digital audio and video content can be played on traditional analog devices.

Secondly, DAC digital analogue converter also plays an important role in communication fields such as wireless communication systems and radar systems. It is used for digital signal demodulation and analog signal generation to ensure communication quality and performance. For example, in the process of digital modulation and demodulation, the DAC digital analogue converter can convert the digital signal to an analog signal for transmission, while the receiver uses an ADC (analog-to-digital converter) to convert the received analog signal back to a digital signal for processing.

Last but not least, DAC digital analogue converter also plays an important role in automation control systems, robot control, aerospace and other relevant control fields. It can convert digital control signals into analog control signals to drive analog actuators (such as motors, valves, etc.) for precise control. By adjusting the output of the DAC digital analogue converter, precise control of the analog actuator can be achieved, thus achieving precise regulation and monitoring of the system state.

Final Verdict

Although DAC digital analogue converter does not get much attention in our daily use of electronic devices, it is an integral part of modern electronic technology. It allows the information of the digital world to be presented in the analog world, allowing us to experience a variety of beautiful sounds and images on a variety of electronic devices.