Datasheet AD7764 (Analog Devices)

24-Bit, 312 kSPS, 109 dB Sigma-Delta ADC with On-Chip Buffers and Serial Interface Data Sheet AD7764 FEATURES FUNCTIONAL BLOCK DIAGRAM High performance 24-bit ∑-∆ ADC VOUTA– VOUTA+ VIN+ VIN– MCLK GND 115 dB dynamic range at 78.125 kHz output data rate AVDD1 VINA+ 109 dB dynamic range at 312.5 kHz output data rate DIFF AVDD2 MULTIBIT VINA– AV Σ-Δ 312.5 kHz maximum fully filtered output word rate DD3 MODULATOR AVDD4 Pin-selectable oversampling rates of 64×, 128×, and 256× DV V DD REF+ Low power mode BUF 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 CORRECTION REGISTERS RBIAS RESET/PWRDWN On-chip reference buffer AD7764 Full band, low-pass, finite impulse response (FIR) filter
001
FSO SCO SDI SDO FSI Overrange alert pin
06518- 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
APPLICATIONS
AD7762 625 kSPS, 109 dB, parallel output, on-chip buffer 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 128/64/32 kSPS, 8.5 mW, 109 dB SNR
Instrumentation
AD7767 128/64/32 kSPS, 8.5 mW, 109 dB SNR
GENERAL DESCRIPTION
The AD7764 is a high performance, 24-bit, sigma-delta (Σ-Δ) 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 excel ent 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 ful 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 −40°C reducing power dissipation without reducing the output data to +85°C. rate or available input bandwidth.
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Document Outline FEATURES APPLICATIONS FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION REVISION HISTORY SPECIFICATIONS TIMING SPECIFICATIONS Timing Diagrams ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS TERMINOLOGY THEORY OF OPERATION Σ-Δ MODULATION AND DIGITAL FILTERING AD7764 ANTIALIAS PROTECTION INPUT STRUCTURE ON-CHIP DIFFERENTIAL AMPLIFIER MODULATOR INPUT STRUCTURE DRIVING THE MODULATOR INPUTS DIRECTLY AD7764 SERIAL INTERFACE READING DATA READING STATUS AND OTHER REGISTERS WRITING TO THE AD7764 FUNCTIONALITY SYNCHRONIZATION OVERRANGE ALERTS POWER MODES Low Power Mode RESETB/PWRDWNB Mode DECIMATION RATE PIN DAISY-CHAINING READING DATA IN DAISY-CHAIN MODE WRITING DATA IN DAISY-CHAIN MODE CLOCKING THE AD7764 MCLK JITTER REQUIREMENTS Example 1 Example 2 DECOUPLING AND LAYOUT INFORMATION SUPPLY DECOUPLING REFERENCE VOLTAGE FILTERING DIFFERENTIAL AMPLIFIER COMPONENTS LAYOUT CONSIDERATIONS USING THE AD7764 BIAS RESISTOR SELECTION AD7764 REGISTERS CONTROL REGISTER STATUS REGISTER GAIN REGISTER—ADDRESS 0x0004 Nonbit Mapped, Default Value: 0xA000 OVERRANGE REGISTER—ADDRESS 0x0005 Nonbit Mapped, Default Value: 0xCCCC OUTLINE DIMENSIONS ORDERING GUIDE