Micropower, Zero Drift, True Rail-to-Rail Instrumentation Amplifier Data Sheet AD8237 FEATURES PIN CONFIGURATION AD8237 Gain set with 2 external resistors Can achieve low gain drift at all gains BW 1 8 V OUT Ideal for battery powered instruments 2 7 +IN + FB Supply current: 115 A IN 3 + 6 REF TOP VIEW V 4 5 +V Rail-to-rail input and output S S (Not to Scale) Zero input crossover distortion Figure 1. Designed for excellent dc performance Minimum CMRR: 106 dB Maximum offset voltage drift: 0.3 V/C Maximum gain error: 0.005% (all gains) Maximum gain drift: 0.5 ppm/C (all gains) Input bias current: 1 nA guaranteed to 125C Bandwidth mode pin (BW) to adjust compensation 8 kV HBM ESD rating RFI filter on-chip Single-supply operation: 1.8 V to 5.5 V 1 Table 1. Instrumentation Amplifiers by Category 8-lead MSOP package General Zero Military Digital Purpose Drift Grade Micropower Gain AD8421 AD8237 AD620 AD8237 AD8250 APPLICATIONS AD8221/AD8222 AD8231 AD621 AD8420 AD8251 Bridge amplification AD8220/AD8224 AD8293 AD524 AD8235/AD8236 AD8253 Pressure measurement AD8228 AD8553 AD526 AD627 AD8231 Medical instrumentation AD8295 AD8556 AD624 Thermocouple interface AD8226 AD8557 Portable systems 1 See www.analog.com for the latest instrumentation amplifiers. Current measurement GENERAL DESCRIPTION The AD8237 is a micropower, zero drift, rail-to-rail input and The AD8237 is available in an 8-lead MSOP package. Performance output instrumentation amplifier. The relative match of two is specified over the full temperature range of 40C to +125C. resistors sets any gain from 1 to 1000. The AD8237 has excellent 6 AD8237 gain accuracy performance that can be preserved at any gain G = 100 5 with two ratio-matched resistors. V = 5V S V = 2.5V REF TRADITIONAL IN-AMP The AD8237 employs the indirect current feedback architecture to 4 (RAIL-TO-RAIL OUT) achieve a true rail-to-rail capability. Unlike conventional in-amps, 3 the AD8237 can fully amplify signals with common-mode voltage at or even slightly beyond its supplies. This enables applications 2 with high common-mode voltages to use smaller supplies and save power. 1 The AD8237 is an excellent choice for portable systems. With a 0 minimum supply voltage of 1.8 V, a 115 A typical supply current, and wide input range, the AD8237 makes full use of a limited 1 0 1 2 3 4 5 power budget, yet offers bandwidth and drift performance suitable OUTPUT VOLTAGE (V) for bench-top systems. Figure 2. Input Common-Mode Voltage vs. Output Voltage, +V = 5 V, G = 100 S Rev. 0 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 www.analog.com 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. Fax: 781.461.3113 2012 Analog Devices, Inc. All rights reserved. INPUT COMMON-MODE VOLTAGE (V) 10289-001 10289-002AD8237 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Clock Feedthrough ..................................................................... 21 Applications ....................................................................................... 1 Input Voltage Range ................................................................... 21 Pin Configuration ............................................................................. 1 Input Protection ......................................................................... 22 General Description ......................................................................... 1 Filtering Radio Frequency Interference .................................. 22 Revision History ............................................................................... 2 Using the Reference Pin ............................................................ 22 Specifications ..................................................................................... 3 Layout .......................................................................................... 23 Absolute Maximum Ratings ............................................................ 7 Input Bias Current Return Path ............................................... 23 Thermal Resistance ...................................................................... 7 Applications Information .............................................................. 25 ESD Caution .................................................................................. 7 Battery Current Monitor ........................................................... 25 Pin Configuration and Function Descriptions ............................. 8 Programmable Gain In-Amp.................................................... 25 Typical Performance Characteristics ............................................. 9 AD8237 in an Electrocardiogram (ECG) Front End............. 26 Theory of Operation ...................................................................... 20 Outline Dimensions ....................................................................... 27 Architecture ................................................................................. 20 Ordering Guide .......................................................................... 27 Setting the Gain .......................................................................... 20 Gain Accuracy............................................................................. 21 REVISION HISTORY 8/12Revision 0: Initial Version Rev. 0 Page 2 of 28