Datasheet AD8232 (Analog Devices)

Single-Lead, Heart Rate Monitor Front End Data Sheet AD8232 FEATURES FUNCTIONAL BLOCK DIAGRAM Fully integrated single-lead ECG front end 20 19 18 17 16 HPSENSE IAOUT REFIN +V Low supply current: 170 µA (typical) S GND HPDRIVE Common-mode rejection ratio: 80 dB (dc to 60 Hz) 1 FR 15 S1 10kΩ A3 Two or three electrode configurations +IN High signal gain (G = 100) with dc blocking capabilities 2 AC/DC 14 –IN IA 2-pole adjustable high-pass filter 3 Accepts up to ±300 mV of half cell potential SDN 150kΩ 13 Fast restore feature improves filter settling AD8232 4 Uncommitted op amp LOD+ RLDFB 3-pole adjustable low-pass filter with adjustable gain C1 12 LEADS-OFF 5 A2 Leads off detection: ac or dc options DETECTION RLD LOD– Integrated right leg drive (RLD) amplifier C2 11 Single-supply operation: 2.0 V to 3.5 V S2 Integrated reference buffer generates virtual ground 10kΩ A1 Rail-to-rail output
001
SW OPAMP+ REFOUT OPAMP– OUT 6 7 8 9 10 Internal RFI filter
10866- Figure 1.
8 kV HBM ESD rating Shutdown pin 20-lead 4 mm × 4 mm LFCSP package APPLICATIONS Fitness and activity heart rate monitors Portable ECG Remote health monitors Gaming peripherals Biopotential signal acquisition GENERAL DESCRIPTION
The AD8232 is an integrated signal conditioning block for ECG To improve common-mode rejection of the line frequencies in and other biopotential measurement applications. It is designed the system and other undesired interferences, the AD8232 to extract, amplify, and filter small biopotential signals in the includes an amplifier for driven lead applications, such as right presence of noisy conditions, such as those created by motion or leg drive (RLD). remote electrode placement. This design allows for an ultralow The AD8232 includes a fast restore function that reduces the power analog-to-digital converter (ADC) or an embedded duration of otherwise long settling tails of the high-pass filters. microcontroller to acquire the output signal easily. After an abrupt signal change that rails the amplifier (such as a The AD8232 can implement a two-pole high-pass filter for leads off condition), the AD8232 automatically adjusts to a eliminating motion artifacts and the electrode half-cell potential. higher filter cutoff. This feature allows the AD8232 to recover This filter is tightly coupled with the instrumentation architec- quickly, and therefore, to take valid measurements soon after ture of the amplifier to allow both large gain and high-pass connecting the electrodes to the subject. filtering in a single stage, thereby saving space and cost. The AD8232 is available in a 4 mm × 4 mm, 20-lead LFCSP An uncommitted operational amplifier enables the AD8232 to package. Performance is specified from 0°C to 70°C and is create a three-pole low-pass filter to remove additional noise. operational from −40°C to +85°C. The user can select the frequency cutoff of al filters to suit different types of applications.
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Document Outline Features Applications Functional Block Diagram General Description Revision History Specifications Absolute Maximum Ratings ESD Caution Pin Configuration and Function Descriptions Typical Performance Characteristics Instrumentation Amplifier Performance Curves Operational Amplifier Performance Curves Right Leg Drive (RLD) Amplifier Performance Curves Reference Buffer Performance Curves System Performance Curves Theory of Operation Architecture Overview Instrumentation Amplifier Operational Amplifier Right Leg Drive Amplifier Reference Buffer Fast Restore Circuit Leads Off Detection DC Leads Off Detection AC Leads Off Detection Standby Operation Input Protection Radio Frequency Interference (RFI) Power Supply Regulation and Bypassing Input Referred Offsets Layout Recommendations Applications Information Eliminating Electrode Offsets High-Pass Filtering Two-Pole High-Pass Filter Additional High-Pass Filtering Options Low-Pass Filtering and Gain Driving Analog-to-Digital Converters Driven Electrode Application Circuits Heart Rate Measurement Next to the Heart Exercise Application: Heart Rate Measured at the Hands Cardiac Monitor Configuration Portable Cardiac Monitor with Elimination of Motion Artifacts Packaging and Ordering Information Outline Dimensions Ordering Guide