AN-607 APPLICATION NOTE One Technology Way • P.O. Box 9106 • Norwood, MA 02062-9106, U.S.A. • Tel: 781.329.4700 • Fax: 781.461.3113 • www.analog.com Selecting a Low Bandwidth (<15 kSPS) Sigma-Delta ADC by Mary McCarthy INTRODUCTION PRESSURE MEASUREMENT Analog Devices, Inc., has a wide range of low bandwidth, high resolution Σ-Δ ADCs. Along with the ADC, these devices contain current sources, a multiplexer, a PGA, and analog input buffers on-board. This application note identifies some of the applications in which the ADCs are used and also identifies the most suitable ADCs for each application. Requirements: Low level differential analog inputs with a high level differential reference input for ratiometric operation. Optional features include an auxiliary ADC that can be used for temperature compensation. NUMBER OF BITS 16-Bit: AD7705, AD7706, AD7707, AD7708, AD7709, AD7715, AD7788, AD7790, AD7792, AD7795, AD7796, AD7798 24-Bit: AD7710, AD7711, AD7711A, AD7712, AD7713, AD7714, AD7718, AD7719, AD7730, AD7730L, AD7731, AD7732, AD7734, AD7738, AD7739, AD7782, AD7783, AD7787, AD7789, AD7791, AD7793, AD7794, AD7797, AD7799 MULTICHANNEL APPLICATIONS High Throughput: AD7731, AD7734, AD7738, AD7739 Low Throughput: AD7708/AD7718, AD7714, AD7794/AD7795 TEMPERATURE MEASUREMENT For thermal diode and RTD applications, current sources are required. Thermocouple: AD7714, AD7719, AD7792/AD7793, AD7794/AD7795 Thermal Diode: AD7709 RTD: AD7711, AD7719, AD7783, AD7792/AD7793, AD7794/AD7795 AD7710, AD7714, AD7719, AD7730, AD7798/AD7799 WEIGH SCALE MEASUREMENT Requirements: Low level differential analog inputs with a high level differential reference input for ratiometric operation. Optional features include an auxiliary ADC that can be used for temperature compensation, fast-step, ac excitation, a reference detect circuit, and increased filter rejection in the out-of-band region. AD7714, AD7719, AD7730, AD7730L, AD7796/AD7797, AD7798/AD7799 LOW POWER AD7705/AD7706, AD7714, AD7715, AD7719, AD7787, AD7788/AD7789, AD7790, AD7791, AD7792/AD7793, AD7794/AD7795, AD7796/AD7797, AD7798/AD7799 HIGH ANALOG INPUT VOLTAGES (±10 V) AD7707, AD7712, AD7732, AD7734 RAIL-TO-RAIL ON-CHIP BUFFERS AD7708/AD7718, AD7709, AD7719, AD7782, AD7783, AD7787, AD7790, AD7791 BIPOLAR INPUTS (±2.5 V) AD7710, AD7711, AD7712 PIN CONFIGURABLE AD7782, AD7783 Rev. E | Page 1 of 2 AN-607 Table 1. Summary of Low Bandwidth Σ-Δ ADCs Part No. Bits p-p Resolution @ Max Range (Bits) p-p Resolution @ Data Rate (Hz) AIN Channels AD7701 AD7703 AD7705 AD7706 AD7707 AD7708 AD7709 AD7710 AD7711 AD7711A AD7712 AD7713 AD7714 AD7715 AD7718 AD7719 AD7730 16 20 16 16 16 16 16 24 24 24 24 24 24 16 24 24 24 16 17 16 16 16 16 16 17.5 17.5 17.5 17.5 16 17.5 16 18.5 18.5 17 4000 4000 60 60 60 20 20 60 60 60 60 20 60 60 20 20 200 1 1 2 3 3 10 4 2 2 2 2 3 5 1 10 5 2 Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y AD7730L 24 17 200 2 Y Y AD7731 24 17 800 5 Y Y AD7732 24 16 2000 2 Y Y AD7734 24 16 2000 4 Y Y AD7738 24 16 8500 8 Y Y AD7739 24 16 4000 8 Y Y AD7782 AD7783 AD7787 AD7788 AD7789 AD7790 AD7791 AD7792 AD7793 AD7794 AD7795 AD7796 AD7797 AD7798 24 24 24 16 24 16 24 16 24 24 16 16 24 16 18.5 18.5 19 16 19 16 19 16 19 19 16 15.5 15.5 16 20 20 16.6 16.6 16.6 16.6 16.6 16.6 16.6 16.6 16.6 16.6 16.6 16.6 2 1 2 1 1 1 1 3 3 6 6 1 1 3 Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y AD7799 24 19 16.6 3 Y Y On-Chip PGA On-Chip AIN Buffer Y Y Y Y Y On-Chip Current Source Y Y Y Y ©2006 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. AN03180-0-10/06(E) Rev. E | Page 2 of 2 Y Y Y Y Y AVDD/ DVDD (V) Power Supply Current (mA) Price ($/1k) 5 5 0.3 0.3 0.28 1.28 1.25 5 5 5 5 0.7 0.35 0.35 1.28 1.5 13 15.70 13.26 4.12 4.12 4.46 3.98 3.89 14.45 15.30 15.30 13.20 16.15 8.28 5.65 5.24 8.76 11.60 13 9.55 13.5 9.86 18 8.50 18 8.50 18 7.77 5 5 3/5 3/5 3/5 3/5 3/5 5 5 5 5 5 3/5 3/5 3/5 3/5 AVDD: 5 DVDD: 3/5 AVDD: 5 DVDD: 3/5 AVDD: 5 DVDD: 3/5 AVDD: 5 DVDD: 3/5 AVDD: 5 DVDD: 3/5 AVDD: 5 DVDD: 3/5 AVDD: 5 DVDD: 3/5 3/5 3/5 3/5 3/5 3/5 3/5 3/5 3/5 3/5 3/5 3/5 3/5 3/5 3/5 14 7.65 1.3 1.3 0.13 0.065 0.065 0.13 0.13 0.40 0.40 0.40 0.40 0.25 0.25 0.30 4.25 4.25 3.80 1.99 2.95 2.96 3.83 3.99 5.10 4.80 4.40 2.75 3.35 3.80 3/5 0.38 4.35 Comments 10 Hz bandwidth 10 Hz bandwidth Two current sources One current source Dual ADC Weigh scale Weigh scale Fast channel switching Fast channel switching Fast channel switching Fast channel switching Read-only Read-only Low power Low power Low power Low power Low power On-chip reference On-chip reference High channel count High channel count Weigh scale Weigh scale Weigh scale/ pressure Weigh scale/ pressure