4.8 kHz, Ultralow Noise, 24-Bit Sigma-Delta ADC with PGA and AC Excitation Data Sheet AD7195 FEATURES Chromatography PLC/DCS analog input modules AC or DC sensor excitation Data acquisition RMS noise: 8.5 nV at 4.7 Hz (gain = 128) Medical and scientific instrumentation 16 noise-free bits at 2.4 kHz (gain = 128) Up to 22.5 noise-free bits (gain = 1) GENERAL DESCRIPTION Offset drift: 5 nV/C The AD7195 is a low noise, complete analog front end for high Gain drift: 1 ppm/C precision measurement applications. It contains a low noise, Specified drift over time 24-bit sigma-delta (-) analog-to-digital converter (ADC). 2 differential/4 pseudo differential input channels The on-chip low noise gain stage means that signals of small Automatic channel sequencer amplitude can be interfaced directly to the ADC. The AD7195 Programmable gain (1 to 128) contains ac excitation, which is used to remove dc-induced Output data rate: 4.7 Hz to 4.8 kHz offsets from bridge sensors. Internal or external clock The device can be configured to have two differential inputs or Simultaneous 50 Hz/60 Hz rejection four pseudo differential inputs. The on-chip channel sequencer Power supply AV : 4.75 V to 5.25 V allows several channels to be enabled, and the AD7195 sequentially DD DV : 2.7 V to 5.25 V converts on each enabled channel. This simplifies communication DD Current: 6 mA with the part. The on-chip 4.92 MHz clock can be used as the Temperature range: 40C to +105C clock source to the ADC or, alternatively, an external clock or Package: 32-lead LFCSP crystal can be used. The output data rate from the part can be varied from 4.7 Hz to 4.8 kHz. INTERFACE The device has two digital filter options. The choice of filter 3-wire serial affects the rms noise/noise-free resolution at the programmed SPI, QSPI, MICROWIRE, and DSP compatible output data rate, the settling time, and the 50 Hz/60 Hz rejec- Schmitt trigger on SCLK tion. For applications that require all conversions to be settled, APPLICATIONS the AD7195 includes a zero latency feature. Weigh scales The part operates with a 5 V analog power supply and a digital Strain gage transducers power supply from 2.7 V to 5.25 V. It consumes a current of Pressure measurement 6 mA. It is housed in a 32-lead LFCSP package. Temperature measurement FUNCTIONAL BLOCK DIAGRAM AV DV DD AGND DD DGND REFIN(+) REFIN() REFERENCE DETECT AV DD AIN1 AIN2 AIN3 DOUT/RDY SERIAL AIN4 INTERFACE MUX DIN - PGA AND AINCOM ADC CONTROL SCLK LOGIC CS SYNC BPDSW AGND TEMP SENSOR AC CLOCK EXCITATION CIRCUITRY CLOCK AD7195 ACX1 ACX1 ACX2 ACX2 MCLK1 MCLK2 Figure 1. Rev. A 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 20102017 Analog Devices, Inc. All rights reserved. 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. Technical Support www.analog.com 08771-001AD7195 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Overview ..................................................................................... 25 Interface ............................................................................................. 1 Analog Input Channel ............................................................... 26 Applications ....................................................................................... 1 PGA .............................................................................................. 26 General Description ......................................................................... 1 Reference ..................................................................................... 26 Functional Block Diagram .............................................................. 1 Reference Detect ......................................................................... 26 Revision History ............................................................................... 2 Bipolar/Unipolar Configuration .............................................. 27 Specifications ..................................................................................... 3 Data Output Coding .................................................................. 27 Timing Characteristics ................................................................ 6 Burnout Currents ....................................................................... 27 Absolute Maximum Ratings ............................................................ 8 AC Excitation .............................................................................. 27 Thermal Resistance ...................................................................... 8 Channel Sequencer .................................................................... 28 ESD Caution .................................................................................. 8 Digital Interface .......................................................................... 28 Pin Configuration and Function Descriptions ............................. 9 Reset ............................................................................................. 32 Typical Performance Characteristics ........................................... 11 System Synchronization ............................................................ 32 RMS Noise and Resolution............................................................ 13 Clock ............................................................................................ 32 4 Sinc Chop Disabled ................................................................... 13 Enable Parity ............................................................................... 32 3 Sinc Chop Disabled ................................................................... 14 Temperature Sensor ................................................................... 32 4 Sinc Chop Enabled .................................................................... 15 Bridge Power-Down Switch ...................................................... 33 3 Sinc Chop Enabled .................................................................... 16 Calibration................................................................................... 33 On-Chip Registers .......................................................................... 17 Digital Filter ................................................................................ 34 4 Communications Register ......................................................... 18 Sinc Filter (Chop Disabled) ..................................................... 34 3 Status Register ............................................................................. 19 Sinc Filter (Chop Disabled) ..................................................... 36 4 Mode Register ............................................................................. 19 Chop Enabled (Sinc Filter) ...................................................... 38 3 Configuration Register .............................................................. 21 Chop Enabled (Sinc Filter) ...................................................... 40 Data Register ............................................................................... 23 Summary of Filter Options ....................................................... 41 ID Register ................................................................................... 23 Grounding and Layout .............................................................. 42 GPOCON Register ..................................................................... 23 Applications Information .............................................................. 43 Offset Register ............................................................................. 24 Weigh Scales ................................................................................ 43 Full-Scale Register ...................................................................... 24 Outline Dimensions ....................................................................... 44 ADC Circuit Information .............................................................. 25 Ordering Guide .......................................................................... 44 REVISION HISTORY 7/2017Rev. A to Rev. B Changed CP-32-11 to CP-32-12 .................................. Throughout Changes to Table 5 .......................................................................... 10 Updated Outline Dimensions ....................................................... 44 Changes to Ordering Guide .......................................................... 44 1/2010Revision 0: Initial Version Rev. A Page 2 of 44