14-Bit, 250 kSPS PulSAR, Pseudo Differential ADC in MSOP/LFCSP Data Sheet AD7942 FEATURES APPLICATION DIAGRAM 0.5V TO 5V 2.5V TO 5V 14-bit resolution with no missing codes Throughput: 250 kSPS INL: 0.4 LSB typical, 1 LSB maximum (0.0061% of FSR) SINAD: 85 dB at 20 kHz VIO 1.8V TO VDD REF VDD 0V TO V REF SDI THD: 100 dB at 20 kHz IN+ SCK AD7942 3- OR 4-WIRE INTERFACE Pseudo differential analog input range IN (SPI, DAISY CHAIN, CS) SDO 0 V to V with V up to VDD REF REF GND CNV No pipeline delay Single-supply 2.3 V to 5.5 V operation with 1.8 V/2.5 V/3 V/5 V logic interface Figure 1. Proprietary serial interface 1 SPI-/QSPI-/MICROWIRE-/DSP-compatible GENERAL DESCRIPTION Daisy-chaining for multiple ADCs and busy indicator The AD7942 is a 14-bit, charge redistribution, successive approxi- Power dissipation mation PulSAR ADC that operates from a single power supply, 1.25 mW at 2.5 V/100 kSPS, 3.6 mW at 5 V/100 kSPS VDD, between 2.3 V to 5.5 V. It contains a low power, high 1.25 W at 2.5 V/100 SPS speed, 14-bit sampling ADC with no missing codes, an internal Standby current: 1 nA conversion clock, and a versatile serial interface port. The part 10-lead package: MSOP and 3 mm 3 mm LFCSP also contains a low noise, wide bandwidth, short aperture delay Pin-for-pin compatible with the 16-bit AD7685 track-and-hold circuit. On the CNV rising edge, it samples an APPLICATIONS analog input, IN+, between 0 V to VREF with respect to a ground sense, IN. The reference voltage, V REF, is applied externally and Battery-powered equipment is set up to be the supply voltage. Its power scales linearly with Data acquisition the throughput. Instrumentation Medical instruments The SPI-compatible serial interface also features the ability, Process controls using the SDI input, to daisy-chain several ADCs on a single 3-wire bus and provides an optional busy indicator. It is com- patible with 1.8 V, 2.5 V, 3 V, or 5 V logic using a separate supply (VIO). The AD7942 is housed in a 10-lead MSOP or a 10-lead LFCSP package yet fits in the same size footprint as the 8-lead MSOP or SOT-23. Operation for the AD7942 is specified from 40C to +85C. 1 Protected by U.S. Patent 6,703,961. Table 1. MSOP, LFCSP/SOT-23, 14-/16-/18-Bit 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-x 1 1 1 AD7683 AD7687 AD7688 AD7983 ADA4841-x 1 AD7684 AD7694 AD7693 1 1 1 18-Bit AD7691 AD7690 AD7982 ADA4941-x 1 AD7984 ADA4841-x 1 Pin-for-pin compatible to the AD7942. 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 20052014 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. 04657-001AD7942 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Terminology .................................................................................... 12 Applications ....................................................................................... 1 Theory of Operation ...................................................................... 13 Application Diagram ........................................................................ 1 Circuit Information .................................................................... 13 General Description ......................................................................... 1 Converter Operation .................................................................. 13 Revision History ............................................................................... 2 Typical Connection Diagram ................................................... 14 Specif icat ions ..................................................................................... 3 Digital Interface .......................................................................... 16 Timing Specifications .................................................................. 5 Application Hints ........................................................................... 23 Absolute Maximum Ratings ............................................................ 7 Layout .......................................................................................... 23 ESD Caution .................................................................................. 7 Evaluating the Performance of AD7942 .................................. 23 Pin Configuration and Function Descriptions ............................. 8 Outline Dimensions ....................................................................... 24 Typical Performance Characteristics ............................................. 9 Ordering Guide .......................................................................... 24 REVISION HISTORY 6/14Rev. B to Rev. C 12/07Rev. 0 to Rev. A Changed QFN (LFCSP) Notation to LFCSP .............. Throughout Changes to Table 1 ............................................................................. 1 Added Patent Footnote .................................................................... 1 Changes to General Description Section ....................................... 1 Changes to Evaluating the Performance of the AD7942 ........... 23 Changes to Table 6 ............................................................................. 7 Changes to Ordering Guide .......................................................... 24 Changes to Table 7 ............................................................................. 8 Changes to Circuit Information Section ..................................... 13 6/08Rev. A to Rev. B Changes to Table 9 .......................................................................... 15 Changes to Features Section and General Description Section . 1 Changes to Figure 39 ...................................................................... 21 Moved Figure 2 and Figure 3 .......................................................... 6 Changes to Figure 41 ...................................................................... 22 Changes to Table 6 ............................................................................ 8 Updated Outline Dimensions ....................................................... 24 Moved Terminology Section ......................................................... 12 Changes to Ordering Guide .......................................................... 24 Changes to Figure 41 ...................................................................... 22 3/05Revision 0: Initial Version Changes to Ordering Guide .......................................................... 24 Rev. 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