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AD7195 Dataheets PDF



Part Number AD7195
Manufacturers Analog Devices
Logo Analog Devices
Description 24-BIT SIGMA-DELTA ADC
Datasheet AD7195 DatasheetAD7195 Datasheet (PDF)

4.8 kHz, Ultralow Noise, 24-Bit Sigma-Delta ADC with PGA and AC Excitation AD7195 www.DataSheet4U.com FEATURES AC or DC sensor excitation RMS noise: 8.5 nV at 4.7 Hz (gain = 128) 16 noise-free bits at 2.4 kHz (gain = 128) Up to 22.5 noise-free bits (gain = 1) Offset drift: 5 nV/°C Gain drift: 1 ppm/°C Specified drift over time 2 differential/4 pseudo differential input channels Automatic channel sequencer Programmable gain (1 to 128) Output data rate: 4.7 Hz to 4.8 kHz Internal or external cloc.

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4.8 kHz, Ultralow Noise, 24-Bit Sigma-Delta ADC with PGA and AC Excitation AD7195 www.DataSheet4U.com FEATURES AC or DC sensor excitation RMS noise: 8.5 nV at 4.7 Hz (gain = 128) 16 noise-free bits at 2.4 kHz (gain = 128) Up to 22.5 noise-free bits (gain = 1) Offset drift: 5 nV/°C Gain drift: 1 ppm/°C Specified drift over time 2 differential/4 pseudo differential input channels Automatic channel sequencer Programmable gain (1 to 128) Output data rate: 4.7 Hz to 4.8 kHz Internal or external clock Simultaneous 50 Hz/60 Hz rejection Power supply AVDD: 4.75 V to 5.25 V DVDD: 2.7 V to 5.25 V Current: 6 mA Temperature range: –40°C to +105°C Package: 32-lead LFCSP Chromatography PLC/DCS analog input modules Data acquisition Medical and scientific instrumentation GENERAL DESCRIPTION The AD7195 is a low noise, complete analog front end for high precision measurement applications. It contains a low noise, 24-bit sigma-delta (Σ-Δ) analog-to-digital converter (ADC). The on-chip low noise gain stage means that signals of small amplitude can be interfaced directly to the ADC. The AD7195 contains ac excitation, which is used to remove dc-induced offsets from bridge sensors. The device can be configured to have two differential inputs or four pseudo differential inputs. The on-chip channel sequencer allows several channels to be enabled, and the AD7195 sequentially converts on each enabled channel. This simplifies communication with the part. The on-chip 4.92 MHz clock can be used as the clock source to the ADC or, alternatively, an external clock or crystal can be used. The output data rate from the part can be varied from 4.7 Hz to 4.8 kHz. The device has two digital filter options. The choice of filter affects the rms noise/noise-free resolution at the programmed output data rate, the settling time, and the 50 Hz/60 Hz rejection. For applications that require all conversions to be settled, the AD7195 includes a zero latency feature. The part operates with a 5 V analog power supply and a digital power supply from 2.7 V to 5.25 V. It consumes a current of 6 mA. It is housed in a 32-lead LFCSP package. INTERFACE 3-wire serial SPI, QSPI™, MICROWIRE™, and DSP compatible Schmitt trigger on SCLK APPLICATIONS Weigh scales Strain gage transducers Pressure measurement Temperature measurement AVDD AGND DVDD DGND FUNCTIONAL BLOCK DIAGRAM REFIN(+) REFIN(–) REFERENCE DETECT AIN1 AIN2 AIN3 AIN4 AINCOM AVDD SERIAL INTERFACE AND CONTROL LOGIC DOUT/RDY DIN SCLK CS SYNC BPDSW AGND TEMP SENSOR MUX PGA Σ-Δ ADC AD7195 ACX1 ACX1 AC EXCITATION CLOCK CLOCK CIRCUITRY 08771-001 ACX2 ACX2 MCLK1 MCLK2 Figure 1. Rev. 0 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 rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 ©2010 Analog Devices, Inc. All rights reserved. AD7195 TABLE OF CONTENTS Features .............................................................................................. 1  Interface ............................................................................................. 1  Applications ....................................................................................... 1  General Description ......................................................................... 1  Functional Block Diagram .............................................................. 1  Revision History ............................................................................... 2  Specifications..................................................................................... 3  Timing Characteristics ................................................................ 6  Absolute Maximum Ratings............................................................ 8  Thermal Resistance ...................................................................... 8  ESD Caution .................................................................................. 8  Pin Configuration and Function Descriptions ............................. 9  Typical Performance Characteristics ........................................... 11  RMS Noise and Resolution............................................................ 13  Sinc Chop Disabled ................................................................... 13  4 3 4 3 www.DataSheet4U.com Overview ..................................................................................... 25  Analog Input Channel ............................................................... 26  PGA ...........................................


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