24-Bit, 312 kSPS, 109 dB Sigma-Delta ADC with On-Chip Buffers and Serial Interface Data Sheet AD7764 FEATURES FUNCTIONAL BLOCK DIAGRAM V A V A+ V + V MCLK GND OUT OUT IN IN High performance 24-bit - ADC 115 dB dynamic range at 78.125 kHz output data rate AV 1 DD V A+ IN 109 dB dynamic range at 312.5 kHz output data rate AV 2 DIFF DD MULTIBIT V A AV 3 IN - DD 312.5 kHz maximum fully filtered output word rate MODULATOR AV 4 DD Pin-selectable oversampling rates of 64, 128, and 256 DV DD V + REF BUF Low power mode RECONSTRUCTION OVERRANGE Flexible serial peripheral interface (SPI) REFGND DECIMATION DEC RATE Fully differential modulator input SYNC INTERFACE LOGIC AND On-chip differential amplifier for signal buffering OFFSET AND GAIN FIR FILTER ENGINE R CORRECTION REGISTERS BIAS RESET/PWRDWN On-chip reference buffer AD7764 Full band, low-pass, finite impulse response (FIR) filter FSO SCO SDI SDO FSI Overrange alert pin Figure 1. Digital gain correction registers Power-down mode Table 1. Related Devices Synchronization of multiple devices via the SYNC pin Device No. Description Daisy chaining AD7760 2.5 MSPS, 100 dB, parallel output, on-chip buffer AD7762 625 kSPS, 109 dB, parallel output, on-chip buffer APPLICATIONS AD7763 625 kSPS, 109 dB, serial output, on-chip buffers Data acquisition systems AD7765 156 kSPS, 112 dB, serial output, on-chip buffers Vibration analysis AD7766 128 kSPS/64 kSPS/32 kSPS, 8.5 mW, 109 dB SNR Instrumentation AD7767 128 kSPS/64 kSPS/32 kSPS, 8.5 mW, 109 dB SNR GENERAL DESCRIPTION The AD7764 is a high performance, 24-bit, sigma-delta (-) The differential input is sampled at up to 40 MSPS by an analog analog-to-digital converter (ADC). It combines wide input band- modulator. The modulator output is processed by a series of width, high speed, and performance of 109 dB dynamic range at a low-pass filters. The external clock frequency applied to the 312.5 kHz output data rate. With excellent dc specifications, the AD7764 determines the sample rate, filter corner frequencies, converter is ideal for high speed data acquisition of ac signals and output word rate. where dc data is also required. The AD7764 device boasts a full band, on-board FIR filter. The Using the AD7764 eases front-end antialias filtering requirements, full stop-band attenuation of the filter is achieved at the Nyquist simplifying the design process significantly. The AD7764 offers frequency. This feature offers increased protection from signals pin-selectable decimation rates of 64, 128, and 256. Other that lie above the Nyquist frequency being aliased back into the features include an integrated buffer to drive the reference, as input signal bandwidth. well as a fully differential amplifier to buffer and level shift the The reference voltage supplied to the AD7764 determines the input to the modulator. input range. With a 4 V reference, the analog input range is An overrange alert pin indicates when an input signal exceeds 3.2768 V differential, biased around a common mode of the acceptable range. The addition of internal gain and internal 2.048 V. This common-mode biasing is achieved using the overrange registers makes the AD7764 a compact, highly on-chip differential amplifier, further reducing the external integrated data acquisition device requiring minimal peripheral signal conditioning requirements. components. The AD7764 is available in a 28-lead TSSOP package and is The AD7764 also offers a low power mode, significantly specified over the industrial temperature range of 40C reducing power dissipation without reducing the output data to +85C. rate or available input bandwidth. Rev. C Document Feedback Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 20072018 Analog Devices, Inc. All rights reserved. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Technical Support www.analog.com Trademarks and registered trademarks are the property of their respective owners. 06518-001AD7764 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Synchronization .......................................................................... 25 Applications ....................................................................................... 1 Overrange Alerts ........................................................................ 25 General Description ......................................................................... 1 Power Modes ............................................................................... 26 Revision History ............................................................................... 2 Decimation Rate Pin .................................................................. 26 Specifications ..................................................................................... 4 Daisy-Chaining ............................................................................... 27 Timing Specifications .................................................................. 7 Reading Data in Daisy-Chain Mode ....................................... 27 Absolute Maximum Ratings ............................................................ 9 Writing Data in Daisy-Chain Mode ........................................ 28 ESD Caution .................................................................................. 9 Clocking the AD7764 .................................................................... 29 Pin Configuration and Function Descriptions ........................... 10 MCLK Jitter Requirements ....................................................... 29 Typical Performance Characteristics ........................................... 12 Decoupling and Layout Information ........................................... 30 Terminology .................................................................................... 16 Supply Decoupling ..................................................................... 30 Theory of Operation ...................................................................... 17 Reference Voltage Filtering ....................................................... 30 - Modulation and Digital Filtering ..................................... 17 Differential Amplifier Components ........................................ 30 AD7764 Antialias Protection .................................................... 20 Layout Considerations ............................................................... 30 Input Structure ................................................................................ 21 Using the AD7764 ...................................................................... 31 On-Chip Differential Amplifier ............................................... 22 Bias Resistor Selection ............................................................... 31 Modulator Input Structure ........................................................ 23 AD7764 Registers ........................................................................... 32 Driving the Modulator Inputs Directly ................................... 23 Control Register ......................................................................... 32 AD7764 Serial Interface ................................................................. 24 Status Register ............................................................................. 32 Reading Data ............................................................................... 24 Gain RegisterAddress 0x0004 ............................................... 33 Reading Status and Other Registers ......................................... 24 Overrange RegisterAddress 0x0005 ..................................... 33 Writing to the AD7764 .............................................................. 24 Outline Dimensions ....................................................................... 34 Functionality ................................................................................... 25 Ordering Guide .......................................................................... 34 REVISION HISTORY 1/2018Rev. B to Rev. C Change to Table 7 ........................................................................... 17 Change to On-Chip Differential Amplifier Section .................. 22 Added Table 8 and Table 9 ............................................................ 18 Changes to On-Chip Differential Amplifier Section 3/2017Rev. A to Rev. B and Table 10 .................................................................................... 21 Changes to Features Section and General Description Section ....... 1 Changes to AD7764 Serial Interface Section Title and Reading Changes to Table 2 ............................................................................ 3 Data Section .................................................................................... 23 Changes to Table 3 ............................................................................ 6 Changes to Functionality Section Title ....................................... 24 Change to Figure 3 Caption and Figure 4 Caption ...................... 7 Changes to Table 14 ....................................................................... 25 Changes to Table 4 ............................................................................ 8 Changes to Table 15 ....................................................................... 26 Changes to Table 5 ............................................................................ 9 Changes to Table 17, Table 18, and Table 19 ............................... 31 Added Figure 29 Renumbered Sequentially .............................. 14 Changes to Terminology Section.................................................. 15 Changes to - Modulation and Digital Filtering Section and Table 6 ....................................................................................... 16 Added Figure 34 .............................................................................. 17 Rev. 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