Ultralow Power, Low Distortion, Fully Differential ADC Drivers Data Sheet ADA4940-1/ADA4940-2 FEATURES FUNCTIONAL BLOCK DIAGRAMS ADA4940-1 Small signal bandwidth: 260 MHz Ultralow power 1.25mA Extremely low harmonic distortion 122 dB THD at 50 kHz FB 1 12 DISABLE 96 dB THD at 1 MHz +IN 2 11 OUT Low input voltage noise: 3.9 nV/Hz IN 3 10 +OUT +FB 4 9 V 0.35 mV maximum offset voltage OCM Balanced outputs Settling time to 0.1%: 34 ns Rail-to-rail output: V + 0.1 V to +V 0.1 V S S NOTES Adjustable output common-mode voltage 1. CONNECT THE EXPOSED PAD TO V OR GROUND. S Flexible power supplies: 3 V to 7 V (LFCSP) Figure 1. ADA4940-1 Disable pin to reduce power consumption ADA4940-1 is available in LFCSP and SOIC packages APPLICATIONS Low power PulSAR/SAR ADC drivers IN1 1 18 +OUT1 Single-ended-to-differential conversion V +FB1 2 17 OCM1 Differential buffers +V 16 V S1 3 S2 ADA4940-2 V +V 15 S1 4 S2 Line drivers FB2 5 14 DISABLE2 Medical imaging +IN2 6 13 OUT2 Industrial process controls Portable electronics GENERAL DESCRIPTION NOTES 1. CONNECT THE EXPOSED PAD TO The ADA4940-1/ADA4940-2 are low noise, low distortion fully V OR GROUND. S differential amplifiers with very low power consumption. They Figure 2. ADA4940-2 are an ideal choice for driving low power, high resolution, high The ADA4940-1 is available in a 3 mm 3 mm, 16-lead LFCSP performance SAR and - analog-to-digital converters (ADCs) and an 8-lead SOIC. The ADA4940-2 is available in a 4 mm with resolutions up to 16 bits from dc to 1 MHz on only 1.25 mA 4 mm, 24-lead LFCSP. The pinouts are optimized to facilitate of quiescent current. The adjustable level of the output common- printed circuit board (PCB) layout and minimize distortion. mode voltage allows the ADA4940-1/ADA4940-2 to match the The ADA4940-1/ADA4940-2 are specified to operate over the input common-mode voltage of multiple ADCs. The internal 40C to +125C temperature range. common-mode feedback loop provides exceptional output balance, Table 1. Similar Products to ADA4940-1/ADA4940-2 as well as suppression of even-order harmonic distortion products. ISUPPLY Bandwidth Slew Rate Noise With the ADA4940-1/ADA4940-2, differential gain configurations Product (mA) (MHz) (V/s) (nV/Hz) are easily realized with a simple external feedback network of AD8137 3 110 450 8.25 four resistors determining the closed-loop gain of the amplifier. ADA4932-1 9 560 2800 3.6 The ADA4940-1/ADA4940-2 are fabricated using Analog Devices, ADA4941-1 2.2 31 22 5.1 Inc., SiGe complementary bipolar process, enabling them to Table 2. Complementary Products to ADA4940-1/ADA4940-2 achieve very low levels of distortion with an input voltage noise Power Throughput Resolution SNR of only 3.9 nV/Hz. The low dc offset and excellent dynamic Product (mW) (MSPS) (Bits) (dB) performance of the ADA4940-1/ADA4940-2 make them well AD7982 7.0 1 18 98 AD7984 10.5 1.333 18 96.5 suited for a variety of data acquisition and signal processing AD7621 65 3 16 88 applications. AD7623 45 1.333 16 88 Rev. E 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 20112018 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. 08452-001 07429-202 IN2 7 24 +IN1 +V 5 16 V S S +FB2 8 23 FB1 +V 6 15 V S +V 9 22 V S S2 S1 +V 14 V +V 10 21 V 7 S2 S1 S S V 11 20 DISABLE1 8 OCM2 +V 13 V S S 19 +OUT2 12 OUT1ADA4940-1/ADA4940-2 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Applications Information .............................................................. 23 Applications ....................................................................................... 1 Analyzing an Application Circuit ............................................ 23 General Description ......................................................................... 1 Setting the Closed-Loop Gain .................................................. 23 Functional Block Diagrams ............................................................. 1 Estimating the Output Noise Voltage ...................................... 23 Revision History ............................................................................... 3 Impact of Mismatches in the Feedback Networks ................. 24 Specifications ..................................................................................... 4 Calculating the Input Impedance of an Application Circuit 24 V = 5 V .......................................................................................... 4 Input Common-Mode Voltage Range ..................................... 25 S VS = 3 V .......................................................................................... 6 Input and Output Capacitive AC Coupling ............................ 26 Absolute Maximum Ratings ............................................................ 8 Setting the Output Common-Mode Voltage .......................... 26 Thermal Resistance ...................................................................... 8 DISABLE Pin .............................................................................. 26 Maximum Power Dissipation ..................................................... 8 Driving a Capacitive Load ......................................................... 26 ESD Caution .................................................................................. 8 Driving a High Precision ADC ................................................ 27 Pin Configurations and Function Descriptions ........................... 9 Layout, Grounding, and Bypassing .............................................. 28 Typical Performance Characteristics ........................................... 11 ADA4940-1 LFCSP Example .................................................... 28 Test Circuits ..................................................................................... 20 Outline Dimensions ....................................................................... 29 Terminology .................................................................................... 21 Ordering Guide .......................................................................... 30 Definition of Terms .................................................................... 21 Theory of Operation ...................................................................... 22 Rev. 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