Digital-to-Analog Converters

Abstract

The last chapters present design details of ADCs in detail with the focus on SAR ADCs in the Chaps. 2 and 3 and delta-sigma ADCs in the Chaps. 4 and 5. Chapter 6 discusses the test and verification of ADCs as well as the external circuitry around the ADC in an application. This chapter will now complement the topic of data converters with an introduction of digital-to-analog converters (DACs). In industrial applications, they are often used as the controlling element. The system performance will then fully rely on the DAC and the absolute values such as INL, offset or gain are important. If they are used inside a control loop, which will increment or decrement the DAC value, then equal step size is required, which is reflected in the DNL.Similar to ADCs, different architectures are available, which differ in speed and resolution. The most common architectures are the current steering DAC, the string DAC, the R-2R architecture and the delta-sigma approach. Figure 7.1 illustrates their performance in resolution versus conversion rate. This chapter will first briefly discuss the performance parameters of DACs and will then describe the four architectures in more detail.