Biopotential

The AD8233 is an integrated signal conditioning block for electrocardiogram (ECG) and other biopotential measurement applications. It is designed to extract, amplify, and filter small biopotential signals in the presence of noisy conditions, such as those created by motion or remote electrode placement. This design allows an ultralow power analog-to-digital converter (ADC) or an embedded microcontroller to easily acquire the output signal.

The AD8233 implements a two-pole, high-pass filter for eliminating motion artifacts and the electrode half cell potential. This filter is tightly coupled with the instrumentation amplifier architecture to allow both large gain and high-pass filtering in a single stage, thereby saving space and cost.

An uncommitted operational amplifier enables the AD8233 to create a three-pole, low-pass filter to remove additional noise. The user can select the frequency cutoff of all filters to suit different types of applications.

To improve the common-mode rejection of the line frequencies in the system and other undesired interferences, the AD8233 includes a right leg drive (RLD) amplifier for driven electrode applications. The AD8233 includes a fast restore function that reduces the duration of the otherwise long settling tails of the high-pass filters. After an abrupt signal change that rails the amplifier (such as a leads off condition), the AD8233 automatically adjusts to a higher filter cutoff. This feature allows the AD8233 to recover quickly, and therefore, to take valid measurements soon after connecting the electrodes to the subject.

The AD8233 is available in a 2 mm × 1.7 mm, 20-ball WLCSP package and a 150 μm thin die for height constrained applications. Performance is specified from 0°C to 70°C and is operational from −40°C to +85°C.

Applications

• Fitness and activity heart rate monitors
• Portable ECG
• Wearable and remote health monitors
• Gaming peripherals
• Biopotential signal acquisition, such as EMG or EEG

The AD8422 is a high precision, low power, low noise, rail-to-rail instrumentation amplifier that delivers the best performance per unit microampere in the industry. The AD8422 processes signals with ultralow distortion performance that is load independent over its full output range.

The AD8422 is the third generation development of the industry standard AD620. The AD8422 employs new process technologies and design techniques to achieve higher dynamic range and lower errors than its predecessors, while consuming less than one-third of the power. The AD8422 uses the high performance pinout introduced by the AD8221.

Very low bias current makes the AD8422 error-free with high source impedance, allowing multiple sensors to be multiplexed to the inputs. Low voltage noise and low current noise make the AD8422 an ideal choice for measuring a Wheatstone bridge.

The wide input range and rail-to-rail output of the AD8422 bring all of the benefits of a high performance in-amp to single-supply applications. Whether using high or low supply voltages, the power savings make the AD8422 an excellent choice for high channel count or power sensitive applications.

The AD8422 uses robust input protection that ensures reliability without sacrificing noise performance. The AD8422 has high ESD immunity, and the inputs are protected from continuous voltages up to 40 V from the opposite supply rail.

A single resistor sets the gain from 1 to 1000. The reference pin can be used to apply a precise offset to the output voltage.

The AD8422 is specified from −40°C to +85°C for the 8-lead MSOP and the 8-lead SOIC_N and from −40°C to +125°C for the 8-lead LFCSP.

APPLICATIONS

• Medical instrumentation
• Industrial process controls
• Strain gages
• Transducer interfaces
• Precision data acquisition systems
• Channel-isolated systems
• Portable instrumentation

The AD8232 is an integrated signal conditioning block for ECG and other biopotential measurement applications. It is designed to extract, amplify, and filter small biopotential signals in the presence of noisy conditions, such as those created by motion or remote electrode placement. This design allows for an ultralow power analog-to-digital converter (ADC) or an embedded microcontroller to acquire the output signal easily.

The AD8232 can implement a two-pole high-pass filter for eliminating motion artifacts and the electrode half-cell potential. This filter is tightly coupled with the instrumentation architec-ture of the amplifier to allow both large gain and high-pass filtering in a single stage, thereby saving space and cost.

An uncommitted operational amplifier enables the AD8232 to create a three-pole low-pass filter to remove additional noise. The user can select the frequency cutoff of all filters to suit different types of applications.

To improve common-mode rejection of the line frequencies in the system and other undesired interferences, the AD8232 includes an amplifier for driven lead applications, such as right leg drive (RLD).

The AD8232 includes a fast restore function that reduces the duration of otherwise long settling tails of the high-pass filters. After an abrupt signal change that rails the amplifier (such as a leads off condition), the AD8232 automatically adjusts to a higher filter cutoff. This feature allows the AD8232 to recover quickly, and therefore, to take valid measurements soon after connecting the electrodes to the subject.

The AD8232 is available in a 4 mm × 4 mm, 20-lead LFCSP and a LFCSP_SS package. Performance for the A grade models is specified from 0°C to 70°C and the models are operational from −40°C to +85°C. Performance for the W grade models is specified over the automotive temperature range of −40°C to +105°C.

Applications

• Fitness and activity heart rate monitors
• Portable ECG
• Remote health monitors
• Gaming peripherals
• Biopotential signal acquisition

The ADAS1000 measures electro cardiac (ECG) signals, thoracic impedance, pacing artifacts, and lead-on/lead-off status and output this information in the form of a data frame supplying either lead/vector or electrode data at programmable data rates. Its low power and small size make it suitable for portable, battery-powered applications. The high performance also makes it suitable for higher end diagnostic machines.

The ADAS1000 is a full-featured, 5-channel ECG including respiration and pace detection, while the ADAS1000-1 offers only ECG channels with no respiration or pace features. Similarly, the ADAS1000-2 is a subset of the main device and is configured for gang purposes with only the ECG channels enabled (no respiration, pace, or right leg drive).

The ADAS1000/ADAS1000-1/ADAS1000-2 are designed to simplify the task of acquiring and ensuring quality ECG signals. They provide a low power, small data acquisition system for biopotential applications. Auxiliary features that aid in better quality ECG signal acquisition include multichannel averaged driven lead, selectable reference drive, fast overload recovery, flexible respiration circuitry returning magnitude and phase information, internal pace detection algorithm operating on three leads, and the option of ac or dc lead-off detection. Several digital output options ensure flexibility when monitoring and analyzing signals. Value-added cardiac post processing is executed externally on a DSP, microprocessor, or FPGA. Because ECG systems span different applications, the ADAS1000/ADAS1000-1/ADAS1000-2 feature a power/noise scaling architecture where the noise can be reduced at the expense of increasing power consumption. Signal acquisition channels can be shut down to save power. Data rates can be reduced to save power.

To ease manufacturing tests and development as well as offer holistic power-up testing, the ADAS1000/ADAS1000-1/ADAS1000-2 offer a suite of features, such as dc and ac test excitation via the calibration DAC and cyclic redundancy check (CRC) redundancy testing, in addition to readback of all relevant register address space. The input structure is a differential amplifier input, thereby allowing users a variety of configuration options to best suit their application.

The ADAS1000/ADAS1000-1/ADAS1000-2 are available in two package options, a 56-lead LFCSP package and a 64-lead LQFP package. Both packages are specified over a −40°C to +85°C temperature range.

APPLICATIONS

• Bedside Patient Monitoring
• Portable Telemetry
• Holter
• AED
• Cardiac Defibrillators
• Ambulatory Monitors
• Pace Maker Programmer
• Patient Transport
• Stress testing

The AD8235 is the smallest and lowest power instrumentation amplifier in the industry. It is available in a 1.5 mm × 2.2 mm wafer level chip scale package (WLCSP). The AD8235 draws a maximum quiescent current of 40 μA. In addition, it draws a maximum 500 nA of current during shutdown mode, making it an excellent instrumentation amplifier for battery powered, portable applications.

The AD8235 can operate on supply voltages as low as 1.8 V. The input stage allows for wide rail-to-rail input voltage range without the crossover distortion, common in other designs. The rail-torail output enables easy interfacing to ADCs.

The AD8235 is an excellent choice for signal conditioning. Its low input bias current of 50 pA and high CMRR of 110 dB (G = 100) offer tremendous value for its size and low power. It is specified over the extended industrial temperature range of −40°C to 125°C.

Applications

• Medical instrumentation
• Low-side current sense
• Portable electronics