14-Bit, 2.5 MSPS, PulSAR, 15.5 mW ADC in LFCSP Data Sheet AD7944 FEATURES APPLICATION DIAGRAM 1.8V 14-bit resolution with no missing codes TO 5V 2.5V 2.7V Throughput: 2.5 MSPS (TURBO high), 2.0 MSPS (TURBO low) Low power dissipation VIO BVDD AVDD, 15.5 mW at 2.5 MSPS, with external reference 0V DVDD VIO TURBO TO 28 mW at 2.5 MSPS, with internal reference IN+ SDI 3- OR 4-WIRE V REF AD7944 INTERFACE: INL: 0.25 LSB typical, 1.0 LSB maximum SCK IN SPI, CS, SDO SNR DAISY CHAIN CNV GND REF (TURBO = LOW) 84 dB, with on-chip reference 84.5 dB, with external reference 10F 4.096 V internal reference: typical drift of 10 ppm/C Pseudo differential analog input voltage range 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 Logic interface: 1.8 V/2.5 V/2.7 V an internal reference (and buffer), error correction circuits, and Proprietary serial interface a versatile serial interface port. On the rising edge of CNV, the SPI/QSPI/MICROWIRE/DSP compatible AD7944 samples an analog input, IN+, between 0 V and V REF Ability to daisy-chain multiple ADCs with busy indicator with respect to a ground sense, IN. The AD7944 features a 20-lead, 4 mm 4 mm LFCSP (QFN) very high sampling rate turbo mode (TURBO high) and a APPLICATIONS reduced power normal mode (TURBO low) for low power Battery-powered equipment applications where the power is scaled with the throughput. Communications In normal mode (TURBO low), the SPI-compatible serial inter- ATE face also features the ability, using the SDI input, to daisy-chain Data acquisition systems several ADCs on a single 3-wire bus and provide an optional busy Medical instruments indicator. The serial interface is compatible with 1.8 V, 2.5 V, and 2.7 V supplies using the separate VIO supply. GENERAL DESCRIPTION 1 The AD7944 is a 14-bit, 2.5 MSPS successive approximation The AD7944 is available in a 20-lead LFCSP with operation analog-to-digital converter (SAR ADC). It contains a low power, specified from 40C to +85C. high speed, 14-bit sampling ADC, an internal conversion clock, 1 Protected by U.S. Patent 6,703,961. 1 Table 1. MSOP, LFCSP, 14-/16-/18-Bit PulSAR ADCs Type 100 kSPS 250 kSPS 400 kSPS to 500 kSPS 1000 kSPS ADC Driver 2 2 3 14-Bit AD7940 AD7942 AD7946 AD7944 2 2 2 16-Bit AD7680 AD7685 AD7686 AD7980 ADA4941-1 2 2 2 AD7683 AD7687 AD7688 AD7983 ADA4841-1 2 3 AD7684 AD7694 AD7693 AD7985 AD8021 2 2 2 18-Bit AD7691 AD7690 AD7982 ADA4941-1 2 AD7984 ADA4841-1 3 AD7986 AD8021 1 See www.analog.com for the latest selection of PulSAR ADCs and ADC drivers. 2 Pin-for-pin compatible with all other parts marked with this endnote. 3 The AD7944, AD7985, and AD7986 are pin-for-pin compatible. 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 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. 04658-001AD7944 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Analog Inputs ............................................................................. 15 Applications ....................................................................................... 1 Driver Amplifier Choice ........................................................... 15 General Description ......................................................................... 1 Voltage Reference Input ............................................................ 16 Application Diagram ........................................................................ 1 Power Supply ............................................................................... 16 Revision History ............................................................................... 2 Digital Interface .............................................................................. 17 Specifications ..................................................................................... 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 Applications Information .............................................................. 25 Circuit Information .................................................................... 13 Layout .......................................................................................... 25 Converter Operation .................................................................. 13 Evaluating AD7944 Performance ............................................. 25 Conversion Modes of Operation .............................................. 13 Outline Dimensions ....................................................................... 27 Typical Application Diagram .................................................... 14 Ordering Guide .......................................................................... 27 REVISION HISTORY 2/16Rev. B to Rev. C 7/14Rev. A to Rev. B Changes to Table 1 ............................................................................ 1 Changes to Features Section ............................................................ 1 Change to Transition Noise Parameter, Table 2 ........................... 3 Added Patent Note, Note 1 ............................................................... 1 Deleted Note 4, Table 2 .................................................................... 3 Changes to Figure 21...................................................................... 13 Changes to Figure 4 .......................................................................... 7 Changes to Data Reading Options Section ................................. 18 Changed Typical Connection Diagram Section to Typical Application Diagram Section ........................................................ 14 8/10Rev. 0 to Rev. A Change to Typical Application Diagram Section ....................... 14 Changes to Table 4, Conversion Time: CNV Rising Edge Changes to Figure 23 ...................................................................... 14 to Data Available ................................................................................ 5 Changes to Driver Amplifier Choice Section ............................. 15 Change to Reference Decoupling Section ................................... 16 10/09Revision 0: Initial Version Changes to Reading During Conversion, Fast Host (Turbo or Normal Mode) Section and Split Reading, Any Speed Host (Turbo or Normal Mode) Section ................................................ 18 Changes to Figure 31 ...................................................................... 21 Changes to Evaluating AD7944 Performance Section .............. 25 Updated Outline Dimensions ....................................................... 27 Changes to Ordering Guide .......................................................... 27 Rev. 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