18-Bit, 2 MSPS, PulSAR 15 mW ADC in LFCSP Data Sheet AD7986 FEATURES TYPICAL APPLICATION CIRCUIT 1.8V 18-bit resolution with no missing codes V+ TO 5V 2.5V 2.7V Throughput: 2 MSPS (TURBO = high), 1.5 MSPS (TURBO = low) 10 Low power dissipation 0V BVDD VIO AVDD, TO 15 mW at 2 MSPS, with external reference 1.5nF DVDD V VIO REF TURBO IN+ 26 mW at 2 MSPS with internal reference V SDI 3- OR 4-WIRE AD7986 INTERFACE: INL: 1 LSB typical, 2.5 LSB maximum SCK V+ SPI, CS IN SDO SNR DAISY CHAIN CNV (TURBO = LOW) REF GND 95.5 dB, with on-chip reference 10 V REF 97.0 dB, with external reference TO 10F 1.5nF 0V 4.096 V internal reference: typical drift of 10 ppm/C V True differential analog input voltage range: V REF NOTES 0 V to V with V up to 5.0 V REF REF 1. GND REFERS TO REFGND, AGND, AND DGND. Allows use of any input range Figure 1. No pipeline delay GENERAL DESCRIPTION Logic interface: 1.8 V/2.5 V/2.7 V 1 The AD7986 is an 18-bit, 2 MSPS successive approximation, Proprietary serial interface: SPI-/QSPI-/MICROWIRE-/DSP- compatible analog-to-digital converter (ADC). It contains a low power, Ability to daisy-chain multiple ADCs with busy indicator high speed, 18-bit sampling ADC, an internal conversion clock, 20-lead 4 mm 4 mm LFCSP an internal reference (and buffer), error correction circuits, and a versatile serial interface port. On the rising edge of CNV, the APPLICATIONS AD7986 samples the voltage difference between the IN+ and Battery-powered equipment IN pins. The voltages on these pins usually swing in opposite Data acquisition systems phases between 0 V and V . It features a very high sampling REF Medical instruments rate turbo mode (TURBO = high) and a reduced power normal Seismic data acquisition systems mode (TURBO = low) for low power applications where the power is scaled with the throughput. In normal mode (TURBO = low), the SPI-compatible serial interface also features the ability, using the SDI input, to daisy- chain several ADCs on a single 3-wire bus and provide an optional busy indicator. It is compatible with 1.8 V, 2.5 V, and 2.7 V using the separate VIO supply. The AD7986 is available in a 20-lead LFCSP with operation specified from 40C to +85C. 1 Protected by U.S. Patent 6,703,961. Table 1. MSOP, LFCSP 14-/16-/18-Bit PulSAR ADCs Type 100 kSPS 250 kSPS 400 kSPS to 500 kSPS 1000 kSPS ADC Driver 1 1 14-Bit AD7940 AD7942 AD7946 1 1 1 16-Bit AD7680 AD7685 AD7686 AD7980 ADA4941-1 1 1 1 AD7683 ADA4841-1 AD7687 AD7688 AD7983 1 AD7684 AD7694 AD7693 1 1 1 18-Bit AD7691 AD7690 AD7982 ADA4941-1 1 AD7984 ADA4841-1 AD7986 AD8021 1 Pin for pin compatible. Rev. D 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 20092016 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. 07956-001AD7986 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Analog Inputs ............................................................................. 15 Applications ....................................................................................... 1 Driver Amplifier Choice ........................................................... 15 Typical Application Circuit ............................................................. 1 Voltage Reference Input ............................................................ 16 General Description ......................................................................... 1 Power Supply ............................................................................... 16 Revision History ............................................................................... 2 Digital Interface .............................................................................. 17 Specif icat ions ..................................................................................... 3 Data Reading Options ............................................................... 18 Timing Specifications .................................................................. 5 CS Mode, 3-Wire Without Busy Indicator ............................. 19 Absolute Maximum Ratings ............................................................ 6 CS Mode, 3-Wire with Busy Indicator .................................... 20 ESD Caution .................................................................................. 6 CS Mode, 4-Wire Without Busy Indicator ............................. 21 Pin Configuration and Function Descriptions ............................. 7 CS Mode, 4-Wire with Busy Indicator .................................... 22 Typical Performance Characteristics ............................................. 9 Chain Mode Without Busy Indicator ...................................... 23 Terminology .................................................................................... 12 Chain Mode with Busy Indicator ............................................. 24 Theory of Operation ...................................................................... 13 Application Hints ........................................................................... 25 Circuit Information .................................................................... 13 Layout .......................................................................................... 25 Converter Operation .................................................................. 13 Evaluating the Performance of the AD7986 ............................... 25 Conversion Modes of Operation .............................................. 13 Outline Dimensions ....................................................................... 27 Typical Connection Diagram ................................................... 14 Ordering Guide .......................................................................... 27 REVISION HISTORY 3/16Rev. C to Rev. D 8/14Rev. B to Rev. C Changes to Figure 1 and Table 1 ..................................................... 1 Replaced QFN with LFCSP .......................................... Throughout Change to Transition Noise Parameter, Table 2 ........................... 3 Changed Application Diagram Section to Typical Application Deleted Endnote 4, Table 2 .............................................................. 3 Circuit Section ................................................................................... 1 Changes to Figure 4 .......................................................................... 8 Change to Features Section .............................................................. 1 Changes to Figure 23 ...................................................................... 14 Added Patent Note, Note 2 ............................................................... 1 Changes to Driver Amplifier Choice Section ............................. 15 Changed 5 V to 4.096 V, Analog Input Heading, Table 7 ......... 14 Changes to Reference Decoupling Section ................................. 16 Changes to Evaluating the Performance of the AD7986 S ection .............................................................................................. 25 Changes to Reading During Conversion, Fast Host (Turbo or Normal Mode) Section and Split-Reading, Any Speed Host Updated Outline Dimensions ....................................................... 27 (Turbo or Normal Mode) Section ................................................ 18 Changes to Ordering Guide .......................................................... 27 Changes to Figure 30 ...................................................................... 21 3/11Rev. A to Rev. B Changes to Figure 34 ...................................................................... 23 Added Common-Mode Input Range Parameter, Table 2 ............ 3 Changes to Evaluating the Performance of the AD7986 Section .. 25 Updated Outline Dimensions ....................................................... 27 8/10Rev. 0 to Rev. A Changes to Ordering Guide .......................................................... 27 Changes to Conversion Time: CNV Rising Edge to Data Available (Turbo Mode/Normal Mode) Parameter, Table 4 ........ 5 Changes to Figure 32 ...................................................................... 22 4/09Revision 0: Initial Version Rev. D Page 2 of 28