Demystifying ΣΔ ADCs

摘要

These powerful A/D converters offer significant advantages over alternative devices, but some designers don't use ΣΔs because they're unfamiliar with the technology. Here are a few reasons you should take a closer look. ΣΔ A/D converters (ADCs) offer attributes required in process control and weigh-scale applications (e.g., high resolution, high integration, and low cost), but designers often use a successive-approximation-register ADC instead. Why? Because they just don't understand the various types of ΣΔ devices. The analog side of a ΣΔ converter (a l-bit ADC) is very simple. It's the digital side, which performs filtering and decimation, that's more complex. The ΣΔ converter is essentially a digital part that is inexpensive to produce. To understand how it works, you must become familiar with the concepts of oversampling, noise shaping, digital filtering, and decimation.