Healthcare remains firmly under the spotlight during the current pandemic. It has always been a key part of decision and policy making for governments around the globe and is even more so now as we get to grips with the current crisis and plan for a future where the delivery of health services will have to adapt at an ever increasing pace. Technology will play a key part in the ability to cope with future pandemics as well as the growing demand for healthcare services from an aging population as average life expectancies increase. Matthew Johnson, Divisional Marketing Manager at Anglia takes a look at two products from Analog Devices innovative technology product portfolio which when coupled with Analog Devices and Anglia’s system expertise are helping to shape the future of healthcare and creating solutions that positively impact people’s lives.
Healthcare in the 21st Century
Analog Devices have vast experience in the healthcare sector with their products designed and specified for a wide range of health applications in critical care environments measuring vital signs and disease management through to life sciences and imaging systems. More recently they have continued to release innovative products for the emerging segments of the healthcare market which encompasses consumer fitness bands and sport watches along with Telemedicine healthcare wearable devices that integrate biomedical features that would typically only have been found in a hospital setting a decade ago.
A recent Age UK study published in 2019 projects the number of people aged over 85 in the UK will nearly double between 2017 to 2040, this is the age group most likely to require health and care services. Telemedicine technology will become an important part of the strategy to deliver health and care services effectively. For example a wearable device which can monitor vital signs, oxygen saturation (SpO2) and activity levels of a patient and then report this data in real-time via a point-of-care cloud connected system to a clinician, could provide early warning signs of health issues which may be more effectively treated when caught early. This real-time monitoring can be done outside of a normal healthcare environment allowing the patient to retain their independence within the community whilst at the same time reducing pressure on hospital or care home services.
Vital Signs Monitoring
The AD5940 from Analog Devices is a high precision analog front end (AFE) designed for electrochemical-based measurement techniques, like amperometric, voltametric, and impedance measurements that enable the next generation of vital sign monitoring devices and intelligent electrochemical sensors. The analog front end has an ultralow power mode to support portable and battery-powered systems. In addition to this, the device can support high performance and diagnostic-based applications such as those found widely in clinical and lab environments.
The AD5940 AFE incorporates both potentiostat and electrochemical impedance spectroscopy (EIS) functionality on a single chip, allowing for sensor measurement in both time and frequency domains. The device features integrated hardware accelerators for advanced sensor diagnostics, best-in-class low noise for accurate sensor measurements and is designed for low power wearable “always-on” applications.
The AD5940 is designed around three key building blocks: an input receive signal-chain, a waveform generator plus transmit channel, and a sequencer with a discrete Fourier transform (DFT) engine to measure complex impedances. Depending on the use-case, the excitation loop with receiver channel can be configured differently.
Figure 1. AD5940 bioelectric system with biopotential and bioimpedance measurement.
Compared to traditional discrete solutions which pose limitations and require multiple ICs to achieve similar performance, Analog Devices AD5940 AFE single chip solution offers advantages in terms of system accuracy and size flexibility to measure 2-Lead, 3-Lead and 4-Lead electrochemical sensors.
One target application for the AD5940 AFE is monitoring patient stress or mental health by electrodermal activity (EDA) or galvanic skin response (GSR). Monitoring the mental state or stress of a patient is important, since it is proven over time stress might result in chronic diseases such as diabetes, cardiac problems, or cancer. When people become stressed, the sympathetic nervous system of the human body activates sweat glands in the skin which has 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.
Figure 2. EDA or GSR measurement principle
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.
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.
Figure 3. ADXL362 Functional Block Diagram
Unlike other accelerometers that typically use power duty cycling to achieve low power consumption, the 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.
Anglia 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.
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 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 team of field application engineers has extensive experience of working with medical customers, working on several urgent projects during 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.
Visit www.anglia-live.com to see the full range of other Analog Devices products available from Anglia.