16-Bit, 250 kSPS PulSAR ADC in MSOP Data Sheet AD7685 FEATURES TYPICAL APPLICATION CIRCUIT 0.5V TO VDD 2.5V TO 5V 16-bit resolution with no missing codes Throughput: 250 kSPS INL: 0.6 LSB typical, 2 LSB maximum (0.003% of FSR) SINAD: 93.5 dB at 20 kHz VIO 1.8V TO VDD REF VDD 0 TO VREF SDI THD: 110 dB at 20 kHz IN+ SCK AD7685 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 GND REF REF CNV No pipeline delay Single-supply operation 2.3 V to 5.5 V with 1.8 V to 5 V logic interface Figure 2. Proprietary serial interface: SPI-/QSPI-/MICROWIRE-/DSP- compatible Table 1. MSOP, LFCSP/SOT-23 14-/16-/18-Bit PulSAR ADC Daisy-chain multiple ADCs, BUSY indicator 400 kSPS 100 250 to 1000 ADC Power dissipation Type kSPS kSPS 500 kSPS kSPS Driver 1.4 W at 2.5 V/100 SPS 18-Bit True AD7691 AD7690 AD7982 ADA4941 1.35 mW at 2.5 V/100 kSPS, 4 mW at 5 V/100 kSPS Differential AD7982 ADA4841 Standby current: 1 nA 16-Bit True AD7684 AD7687 AD7688 ADA4941 10-lead package: MSOP (MSOP-8 size) and Differential AD7693 ADA4841 3 mm 3 mm LFCSP (SOT-23 size) 16-Bit Pseudo AD7680 AD7685 AD7686 AD7980 ADA4841 Pin-for-pin-compatible with 10-lead MSOP/PulSAR ADCs Differential AD7683 AD7694 14-Bit Pseudo AD7940 AD7942 AD7946 ADA4841 APPLICATIONS Differential Battery-powered equipment Medical instruments GENERAL DESCRIPTION Mobile communications 1 The AD7685 is a 16-bit, charge redistribution successive Personal digital assistants (PDAs) approximation, analog-to-digital converter (ADC) that operates Data acquisition from a single power supply, VDD, between 2.3 V to 5.5 V. It Instrumentation contains a low power, high speed, 16-bit sampling ADC with no Process controls missing codes, an internal conversion clock, and a versatile serial 2.0 POSITIVE INL = +0.33LSB interface port. The part also contains a low noise, wide bandwidth, NEGATIVE INL = 0.50LSB 1.5 short aperture delay, track-and-hold circuit. On the CNV rising edge, it samples an analog input IN+ between 0 V to REF with 1.0 respect to a ground sense IN. The reference voltage, REF, is 0.5 applied externally and can be set up to the supply voltage. 0 Power dissipation scales linearly with throughput. 0.5 The SPI-compatible serial interface also features the ability, using the SDI input, to daisy chain several ADCs on a single 1.0 3-wire bus or provides an optional BUSY indicator. It is 1.5 compatible with 1.8 V, 2.5 V, 3 V, or 5 V logic using the separate supply VIO. 2.0 0 16384 32768 49152 65536 The AD7685 is housed in a 10-lead MSOP or a 10-lead LFCSP CODE with operation specified from 40C to +85C. Figure 1. Integral Nonlinearity vs. Code 1 Protected by U.S. Patent 6,703,961. 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 20042014 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 INL (LSB) 02968-005 02968-001AD7685 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Driver Amplifier Choice ........................................................... 16 Applications ....................................................................................... 1 Voltage Reference Input ............................................................ 16 Typical Application Circuit ............................................................. 1 Power Supply ............................................................................... 16 General Description ......................................................................... 1 Supplying the ADC from the Reference .................................. 17 Revision History ............................................................................... 2 Digital Interface .......................................................................... 17 Specifications ..................................................................................... 3 CS Mode 3-Wire, No BUSY Indicator ..................................... 18 Timing Specifications ....................................................................... 5 CS Mode 3-Wire with BUSY Indicator ................................... 19 Absolute Maximum Ratings ............................................................ 7 CS Mode 4-Wire, No BUSY Indicator ..................................... 20 ESD Caution .................................................................................. 7 CS Mode 4-Wire with BUSY Indicator ................................... 21 Pin Configuration and Function Descriptions ............................. 8 Chain Mode, No BUSY Indicator ............................................ 22 Terminology ...................................................................................... 9 Chain Mode with BUSY Indicator ........................................... 23 Typical Performance Characteristics ........................................... 10 Application Hints ........................................................................... 24 Theory of Operation ...................................................................... 13 Layout .......................................................................................... 24 Circuit Information .................................................................... 13 Evaluating the Performance of the AD7685 ............................... 24 Converter Operation .................................................................. 13 True 16-Bit Isolated Application Example .............................. 25 Typical Connection Diagram.................................................... 14 Outline Dimensions ....................................................................... 26 Analog Inputs .............................................................................. 15 Ordering Guide .......................................................................... 27 REVISION HISTORY Changes to Figure 27 ...................................................................... 14 7/14Rev. C to Rev. D Deleted QFN .................................................................. Throughout Changes to Table 9 .......................................................................... 16 Changed Application Diagram to Typical Application Changes to Figure 32 ...................................................................... 17 Circuit ................................................................................................ 1 Changes to Figure 43 ...................................................................... 22 Change to Features Section ............................................................. 1 Changes to Figure 45 ...................................................................... 23 Added Patent Note, Note 1 .............................................................. 1 Updated Outline Dimensions ....................................................... 26 Changes to Evaluating the Performance of the AD7685 Changes to Ordering Guide .......................................................... 27 Section .............................................................................................. 24 Updated Outline Dimensions ....................................................... 26 12/04Rev. 0 to Rev. A Changes to Ordering Guide .......................................................... 27 Changes to Specifications ................................................................. 3 Changes to Figure 17 Captions ..................................................... 11 8/11Rev. B to Rev. C Changes to Power Supply Section ................................................ 17 Changes to Figure 6 and Table 7 ..................................................... 8 Changes to Digital Interface Section ........................................... 18 Updated Outline Dimensions ....................................................... 26 Changes to Mode 4-Wire No Busy Indicator Section ......... 21 CS Changes to Ordering Guide .......................................................... 27 Changes to CS Mode 4-Wire with Busy Indicator Section ....... 22 Changes to Chain Mode, No Busy Indicator Section ................ 23 3/07Rev. A to Rev. B Changes to Chain Mode with Busy Indicator Section .............. 24 Changes to Features and Table 1..................................................... 1 Added True 16-Bit Isolated Application Example Section ....... 26 Changes to Table 3 ............................................................................ 4 Added Figure 47 ............................................................................. 26 Moved Figure 3 and Figure 4 to Page ............................................. 6 Changes to Ordering Guide .......................................................... 28 Inserted Figure 6 Renumbered Sequentially ................................ 8 Changes to Figure 13 and Figure 14 ............................................. 11 4/04Revision 0: Initial Revision Rev. D Page 2 of 28