Embedded Technology Figure 3. ADXL362 functional block diagram
the effect of increasing the skin conductivity resulting in an impedance drop. Skin impedance monitoring is a voltammetry measurement, an excitation signal can be applied across the unknown impedance (the skin in this example) and the voltage across the impedance measured. The current through the impedance is measured and a discrete Fourier transform (DFT) is performed on the ADC results to then calculate the impedance change. Biochemical analysis is another application area for the AD5940 AFE. This technology uses amperometric/ potentiostat type measurements on a sensor that models a typical electrochemical cell. The sensor will normally be a test strip with reagent where the sample of the material under test is applied. Any analyte that can be oxidized or reduced is a candidate for amperometric measurement. For medical applications, samples of human bodily fluids such as blood, urine, or saliva will commonly be analysed using this technique.
The device is available in a compact 56-ball WLCSP package measuring just 3.6 mm × 4.2 mm and has a specified operating temperature range of −40°C to +85°C. The AD5940 has proven itself to be a versatile solution for applications where high precision biological and chemical sensing is mission-critical, such as industrial gas sensing, liquid analysis, material sensing, vital signs monitoring, impedance spectroscopy and disease management.
Activity monitoring
The high levels of integration and versatility of the AD5940 AFE also make it ideal for use in Telemedicine devices, especially when used in combination with other products such as a MEMS accelerometer. The resulting home healthcare wearable device can be a very useful tool in assisted living and social care environments for those living with pre-existing health conditions or the vulnerable & elderly.
The ADXL362 from Analog Devices is an ultralow power, digital output, 3-axis MEMS accelerometer that consumes less than 2 μA at a 100 Hz output data rate and 270 nA when in motion triggered wake-up mode making it ideal for use in battery powered wearable Telemedicine devices. Unlike other accelerometers that typically use power duty cycling to achieve low power consumption, the
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ADXL362 does not alias input signals by under-sampling; it samples the full bandwidth of the sensor at all data rates. In addition to its ultralow power consumption, the ADXL362 has many features to enable true system level power reduction. It includes a deep multimode output FIFO, a built-in micropower temperature sensor, and several activity detection modes including adjustable threshold sleep and wake-up operation. Furthermore, the ADXL362 has provisions for external control of sampling time and/or an external clock.
The ADXL362 3-axis MEMS accelerometer operates on a wide 1.6 V to 3.5 V supply range, and can interface, if necessary, to a host operating on a separate, lower supply voltage. The device is available in a 3 mm × 3.25 mm × 1.06 mm package.
Design Support
Anglia offers comprehensive design support via a range of Analog Devices evaluation tools for the AD5940 AFE and ADXL362 MEMS accelerometer devices. The AD5940 AFE has two evaluation board options, one designed for bio-impedance applications including Body Impedance Analysis (BIA) and Electrodermal Activity (EDA) and another designed for high precision analysis of electrochemical cells.
system and a complete system which allows real-time evaluation, parameter testing, and general familiarization with the ADXL362.
Anglia offer support for customer designs with free evaluation kits and samples of Analog Devices products via the EZYsample service which is available to all registered Anglia Live account customers.
Anglia’s engineering team have extensive experience of working with medical and health technology related applications, they worked on several urgent projects at the start of the recent pandemic as well as many others before that. This expertise is fully available to support customers with all aspects of their designs, offering hands on design support along with access to Analog Devices vast resource of technical application notes and reference designs.
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www.anglia-live.com to see the full range of other Analog Devices products available from Anglia.
The ADXL362 MEMS accelerometer is supported by a number of evaluation boards which include a breakout board that enables easy connection of the micropower, 3-axis, digital output MEMS accelerometer into an existing
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