32 D/A and A/D Converters 32.1 D/A and A/D Circuits D/A and A/D Converter Performance Criteria. D/A Conversion Susan a.r. garrod Processes·D/ A Converter Ics·A/ D Conversion processes·A/D Converter ICs. Grounding and Bypassing on D/A and A/ Purdue University ICs. Selection Criteria for D/A and A/D Converter ICs Digital-to-analog(D/A) conversion is the process of converting digital codes into a continuous range of analog signals. Analog-to-digital (A/D)conversion is the complementary process of converting a continuous range of analog signals into digital codes. Such conversion processes are necessary to interface real-world systems, which typically monitor continuously varying analog signals, with digital systems that process, store, interpret, and manipulate the analog values. D/A and A/D applications have evolved from predominately military-driven applications to consumer- oriented applications. Up to the mid-1980s, the military applications determined the design of many D/A and A/D devices. The military applications required very high performance coupled with hermetic packaging, radiation hardening, shock and vibration testing, and military specification and record keeping. Cost was of little concern, and"low power"applications required approximately 2.8 w. The major applications up the mid 1980s included military radar warning and guidance systems, digital oscilloscopes, medical imaging, infrared systems, and professional video. O The applications requiring D/A and A/D circuits in the 1990s have different performance criteria from those earlier years. In particular, low power and high speed applications are driving the development of D/A and A/D circuits, as the devices are used extensively in battery-operated consumer products. The predominant applications include cellular telephones, hand-held camcorders, portable computers, and set-top cable Tv boxes. These applications generally have low power and long battery life requirements, and they may have high d and high resolution requirements, as is the case with the set-top cable TV boxes 32.1 D/A and A/D Circuits D/A and A/D conversion circuits are available as integrated circuits(ICs) from many manufacturers. a hug array of ICs exists, consisting of not only the D/A or A/D conversion circuits, but also closely related circuits such as sample-and-hold amplifiers, analog multiplexers, voltage-to-frequency and frequency-to-voltage con- verters,voltage references, calibrators, operation amplifiers, isolation amplifiers, instrumentation amplifiers, active filters, dc-to-dc converters, analog interfaces to digital signal processing systems, and data acquisition subsystems. Data books from the IC manufacturers contain an enormous amount of information about these devices and their applications to assist the design engineer. The ICs discussed in this chapter will be strictly the D/A and A/D conversion circuits. Table 32 1 lists a small sample of the variety of the D/A and A/d converters currently available. The ICs usually perform either D/A or A/D conversion. There are serial interface ICs, however, typically for high-performance audio and digital signal processing applications, that perform both A/D and D/a processes c 2000 by CRC Press LLC© 2000 by CRC Press LLC 32 D/A and A/D Converters 32.1 D/A and A/D Circuits D/A and A/D Converter Performance Criteria • D/A Conversion Processes • D/A Converter ICs • A/D Conversion Processes • A/D Converter ICs • Grounding and Bypassing on D/A and A/D ICs • Selection Criteria for D/A and A/D Converter ICs Digital-to-analog (D/A) conversion is the process of converting digital codes into a continuous range of analog signals. Analog-to-digital (A/D) conversion is the complementary process of converting a continuous range of analog signals into digital codes. Such conversion processes are necessary to interface real-world systems, which typically monitor continuously varying analog signals, with digital systems that process, store, interpret, and manipulate the analog values. D/A and A/D applications have evolved from predominately military-driven applications to consumer￾oriented applications. Up to the mid-1980s, the military applications determined the design of many D/A and A/D devices. The military applications required very high performance coupled with hermetic packaging, radiation hardening, shock and vibration testing, and military specification and record keeping. Cost was of little concern, and “low power” applications required approximately 2.8 W. The major applications up the mid- 1980s included military radar warning and guidance systems, digital oscilloscopes, medical imaging, infrared systems, and professional video. The applications requiring D/A and A/D circuits in the 1990s have different performance criteria from those of earlier years. In particular, low power and high speed applications are driving the development of D/A and A/D circuits, as the devices are used extensively in battery-operated consumer products. The predominant applications include cellular telephones, hand-held camcorders, portable computers, and set-top cable TV boxes. These applications generally have low power and long battery life requirements, and they may have high speed and high resolution requirements, as is the case with the set-top cable TV boxes. 32.1 D/A and A/D Circuits D/A and A/D conversion circuits are available as integrated circuits (ICs) from many manufacturers. A huge array of ICs exists, consisting of not only the D/A or A/D conversion circuits, but also closely related circuits such as sample-and-hold amplifiers, analog multiplexers, voltage-to-frequency and frequency-to-voltage con￾verters, voltage references, calibrators, operation amplifiers, isolation amplifiers, instrumentation amplifiers, active filters, dc-to-dc converters, analog interfaces to digital signal processing systems, and data acquisition subsystems. Data books from the IC manufacturers contain an enormous amount of information about these devices and their applications to assist the design engineer. The ICs discussed in this chapter will be strictly the D/A and A/D conversion circuits. Table 32.1 lists a small sample of the variety of the D/A and A/D converters currently available. The ICs usually perform either D/A or A/D conversion. There are serial interface ICs, however, typically for high-performance audio and digital signal processing applications, that perform both A/D and D/A processes. Susan A.R. Garrod Purdue University