SIGMA-DELTA ADCS (CoURTESY OF JAMES M. BRYANT) Because Sigma-Delta is such an important and popular architecture for high resolution(16 to 24 bits) ADCs, the section begins with a basic description of this type of converter. Sigma-Delta Analog-Digital Converters have been known for nearly thirty years, but only recently has the technology(high-density digital vlsi existed to manufacture them as inexpensive monolithic integrated circuits. They are now used in many applications where a low-cost, low-bandwidth, low-power, high-resolution ADC is required There have been innumerable descriptions of the architecture and theory of sigma Delta ADCs but most commence with a maze of integrals and deteriorate from there. In the Applications Department at Analog Devices, we frequently encounter are convinced, from study of a typical published article, that it is too complex to o engineers who do not understand the theory of operation of Sigma-Delta ADCs comprehend easily There is nothing particularly difficult to understand about Sigma-Delta ADCs, as long as you avoid the detailed mathematics, and this section has been written in an attempt to clarify the subject. A Sigma-Delta ADC contains very simple analog electronics (a comparator, a switch, and one or more integrators and analo summing circuits), and quite complex digital computational circuitry. This circuitry consists of a digital signal processor DsP)which acts as a filter(generally, but not invariably, a low pass filter). It is not necessary to know precisely how the filter works to appreciate what it does To understand how a Sigma-Delta ADC works one should be familiar with the concepts of over-sampling, noise shaping, digital filtering and decimation S|GMA- DELTA②2-△ADcs Sigma-Delta ADCs are low-cost and have high resolution excellent DNL, low-power, although limited input bandwidth A∑△ ADC is simple The Mathematics, however is Complex This section Concentrates on What Actually Happens! Figure 3.23 SIGMA-DELTA ADCS (COURTESY OF JAMES M. BRYANT) Because Sigma-Delta is such an important and popular architecture for high resolution (16 to 24 bits) ADCs, the section begins with a basic description of this type of converter. Sigma-Delta Analog-Digital Converters have been known for nearly thirty years, but only recently has the technology (high-density digital VLSI) existed to manufacture them as inexpensive monolithic integrated circuits. They are now used in many applications where a low-cost, low-bandwidth, low-power, high-resolution ADC is required. There have been innumerable descriptions of the architecture and theory of Sigma￾Delta ADCs, but most commence with a maze of integrals and deteriorate from there. In the Applications Department at Analog Devices, we frequently encounter engineers who do not understand the theory of operation of Sigma-Delta ADCs and are convinced, from study of a typical published article, that it is too complex to comprehend easily. There is nothing particularly difficult to understand about Sigma-Delta ADCs, as long as you avoid the detailed mathematics, and this section has been written in an attempt to clarify the subject. A Sigma-Delta ADC contains very simple analog electronics (a comparator, a switch, and one or more integrators and analog summing circuits), and quite complex digital computational circuitry. This circuitry consists of a digital signal processor (DSP) which acts as a filter (generally, but not invariably, a low pass filter). It is not necessary to know precisely how the filter works to appreciate what it does. To understand how a Sigma-Delta ADC works one should be familiar with the concepts of over-sampling, noise shaping, digital filtering. and decimation. SIGMA-DELTA ( - ) ADCs Sigma-Delta ADCs are low-cost and have high resolution, excellent DNL, low-power, although limited input bandwidth A - ADC is Simple The Mathematics, however is Complex This section Concentrates on What Actually Happens! Figure 3.2