TABLE 32.1 D/A and A/D Integrated Circuits Multiplying D/A Converter ICs Resolution, b vs Fixed Reference Settling Time, us Input Data Format Analog Devices AD558 8 Fixed reference parallel Analog Devices AD7524 Multiplying 0.400 Parallel Analog Devices AD390 ad 12 Fixed reference parallel Analog Devices AD1856 16 Fixed reference Serial Burr-Brown DAC729 18 Fixed reference 8 Parallel DATEL DAC-HFS 8 multiplying 0.025 National DACo800 Multiplying parallel A/D Converter ICs Resolution, b Signal Inputs Conversion Speed, Ls Output Data Forma Analog Devices AD572 Serial parallel Burr-Brown ADC803 12 Parallel Burr-Brown adc701 16 National ADC1005B TI. National ADC0808 8 8 100 TI. National ADC0834 TI TLCO820 Parallel TI TLC1540 A/D and D/A Interface ICs Resolution, b On-Board Filters Sampling Rate, kHz Data Format TI TLC32040 19.2(programmable) Serial TI 2914 PCM codec filter 8 Serial D/A and A/D Converter Performance Criteria The major factors that determine the quality of performance of D/A and A/D converters are resolution, sampling The resolution of a D/A circuit is the smallest change in the output analog signal. In an A/D system, the resolution is the smallest change in voltage that can be detected by the system and that can produce a change in the digital code. The resolution determines the total number of digital codes, or quantization levels, that will be recognized or produced by the circuit. The resolution of a D/A or A/D IC is usually specified in terms of the bits in the digital code or in terms of the least significant bit(LSB)of the system. An n-bit code allows for 2" quantization levels, or 2"-1 steps tween quantization levels. As the number of bits increases, the step size between quantization levels decreases, herefore increasing the accuracy of the system when a conversion is made between an analog and digital signal. The system resolution can be specified also as the voltage step size between quantization levels. For A/D circuits, the resolution is the smallest input voltage that is detected by the system The speed of a D/A or A/D converter is determined by the time it takes to perform the conversion process or D/A converters, the speed is specified as the settling time. For A/D converters, the speed is specified as the code; thus, it is specified in the data sheet with the appropriate conditions stated and transition in the digital A/D converters have a maximum sampling rate that limits the speed at which they can perform continuou conversions. The sampling rate is the number of times per second that the analog signal can be sampled and converted into a digital code. For proper A/D conversion, the minimum sampling rate must be at least two times the highest frequency of the analog signal being sampled to satisfy the Nyquist sampling criterion. The nversion speed and other timing factors must be taken into consideration to determine the maximum sampling rate of an A/D converter Nyquist A/D converters use a sampling rate that is slightly more than twice c2000 by CRC Press LLC© 2000 by CRC Press LLC D/A and A/D Converter Performance Criteria The major factors that determine the quality of performance of D/A and A/D converters are resolution, sampling rate, speed, and linearity. The resolution of a D/A circuit is the smallest change in the output analog signal. In an A/D system, the resolution is the smallest change in voltage that can be detected by the system and that can produce a change in the digital code. The resolution determines the total number of digital codes, or quantization levels, that will be recognized or produced by the circuit. The resolution of a D/A or A/D IC is usually specified in terms of the bits in the digital code or in terms of the least significant bit (LSB) of the system. An n-bit code allows for 2n quantization levels, or 2n – 1 steps between quantization levels. As the number of bits increases, the step size between quantization levels decreases, therefore increasing the accuracy of the system when a conversion is made between an analog and digital signal. The system resolution can be specified also as the voltage step size between quantization levels. For A/D circuits, the resolution is the smallest input voltage that is detected by the system. The speed of a D/A or A/D converter is determined by the time it takes to perform the conversion process. For D/A converters, the speed is specified as the settling time. For A/D converters, the speed is specified as the conversion time. The settling time for D/A converters will vary with supply voltage and transition in the digital code; thus, it is specified in the data sheet with the appropriate conditions stated. A/D converters have a maximum sampling rate that limits the speed at which they can perform continuous conversions. The sampling rate is the number of times per second that the analog signal can be sampled and converted into a digital code. For proper A/D conversion, the minimum sampling rate must be at least two times the highest frequency of the analog signal being sampled to satisfy the Nyquist sampling criterion. The conversion speed and other timing factors must be taken into consideration to determine the maximum sampling rate of an A/D converter. Nyquist A/D converters use a sampling rate that is slightly more than twice TABLE 32.1 D/A and A/D Integrated Circuits Multiplying D/A Converter ICs Resolution, b vs. Fixed Reference Settling Time, ms Input Data Format Analog Devices AD558 8 Fixed reference 3 Parallel Analog Devices AD7524 8 Multiplying 0.400 Parallel Analog Devices AD390 Quad, 12 Fixed reference 8 Parallel Analog Devices AD1856 16 Fixed reference 1.5 Serial Burr-Brown DAC729 18 Fixed reference 8 Parallel DATEL DAC-HF8 8 Multiplying 0.025 Parallel National DAC0800 8 Multiplying 0.1 Parallel A/D Converter ICs Resolution, b Signal Inputs Conversion Speed, ms Output Data Format Analog Devices AD572 12 1 25 Serial & parallel Burr-Brown ADC803 12 1 1.5 Parallel Burr-Brown ADC701 16 1 1.5 Parallel National ADC1005B 10 1 50 Parallel TI, National ADC0808 8 8 100 Parallel TI, National ADC0834 8 4 32 Serial TI TLC0820 8 1 1 Parallel TI TLC1540 10 11 21 Serial A/D and D/A Interface ICs Resolution, b On-Board Filters Sampling Rate, kHz Data Format TI TLC32040 14 Yes 19.2 (programmable) Serial TI 2914 PCM codec & filter 8 Yes 8 Serial