HMI and miniature motor control
In next-generation portable home-based medical devices, keypads, light-emitting diodes (LEDs) for backlight and display, touch screens, speakers and miniature motors are becoming more commonplace. As a result, designers face several challenges, including redesigning for rapidly changing customisable HMI controller requirements, smaller form factor, reliability requirements and the provision for improved battery life.
Typically, designers of portable medical applications have relied on microcontrollers, ASSPs or CPLDs to handle HMI and miniature motor control functions. However, microcontrollers and ASSPs do not provide adequate flexibility and CPLDs do not offer the levels of integration or sophistication of FPGAs. Therefore, reprogrammable Flash-based FPGAs, such as Actel’s feature-rich, ultra-low power IGLOO FPGAs, are best suited to serve as flexible HMI or miniature motor controllers.
Display
According to market analyst firm iSuppli, the small-to-medium display (sub-10 inches) is the fastest growing segment of the market. True enough, lower costs and ease of mass manufacturing have increased LCD panel demand in various home-based medical markets. As newer displays with enhanced capabilities and features are continuously being launched, designers are challenged to keep up with these new technologies while minimising cost, size and time to market.
In portable devices, LCDs can consume up to 50% of the application’s power budget, escalating the need for a power-efficient solution. Further, to address LCD display control within portable applications, a low-power, reprogrammable solution is required to adapt to evolving standards and technologies.
Within 1 microsecond, IGLOO devices easily enter and exit Flash*Freeze mode, and consume as little as 5 μW while retaining the contents of the system memory and data registers. As a result, the flash-based IGLOO FPGA can enable both the LCD panel and the controller to function in a power-saving mode with the LCD data and backlight disabled, representing significant battery savings for LCD applications.
Unlike the ASSP display controllers they can displace, Actel’s low-power IGLOO devices can be reprogrammed to adapt and support a variety of LCD displays and changing display technologies, therefore enabling the easy migration between panels as necessary. Further, these feature-rich FPGAs can absorb additional glue logic and more complex LCD controls into a single chip, thereby reducing board area.
Storage
Storage technology has made tremendous progress in the last decade. The rapid advances and ready availability of small form factor Flash storage devices are helping to drive the explosion of portable medical devices in the marketplace. Further, as the storage device market proliferates, with ever-changing protocols and interface standards, design teams are challenged to shrink design cycle times and yet create next-generation portable devices with additional features.
The implementation of each functional block in a medical device will differ depending on the feature demands of the application. Designers can choose from a myriad of sensors to capture and measure physical quantities such as time, temperature, pressure, brightness, positions, speed, PH, gas concentration and levels of chemicals in the blood. These sensors transform the measurement into voltage, current, frequency, capacitance or some other electrical quantity used for processing.
Measured signals can be used by a microcontroller in realtime or they can be stored in an EEPROM or Flash memory, along with the measurement date and time for processing later. Ultra-low-power FPGAs enable the implementation of a variety of storage functions without having to redesign the whole system based on changing storage interface requirements.
Microprocessor
Many medical devices, such as an insulin pump, are typically controlled by a microprocessor. These microprocessors perform various functions, such as processing data from bio-sensors, storing measurements and analysing results. For these applications, designers often select a microprocessor with a rich instruction set and proven track record, ensuring reliable operation and maximising the investment in code generation that can be leveraged in the next-generation medical products.
Developed by ARM in collaboration with Actel, the 32-bit ARM Cortex-M1 processor offers a balance between size, cost and low-power operation when used with Actel’s M1-enabled mixed-signal Fusion and low-power IGLOO FPGAs. Optimised for use in FPGAs, the ARM Cortex-M1 processor runs a subset of the classic Thumb-2 instruction set, so existing Thumb code can be utilised without change.
Clinical applications
From diagnostic lab equipment and drug delivery systems, to automatic external defibrillators (AEDs) and hemodialysis machines, clinical medical devices are often microprocessor-based, electromechanical instruments that use a common set of building blocks: power control and temperature management; a user interface that includes a keypad, LCD monitor, and audio control; Flash or EEPROM for data-logging; and device interfaces for connections to other machines, among others.
Though there are many similarities, individual medical applications are highly use-specific and often very complex. An EKG machine cannot remove waste products from the blood and a haemodialysis machine cannot diagnose heart disease. In addition to their core building block elements, clinical medical devices also include unique functional blocks to complete their task. Ultrasound machines include a transducer probe and transducer pulse controls, but haemodialysis machines use a dialyser.
Changing features and requirements, complex functionality in a small footprint, low power, high accuracy and reliable operation make clinical medical devices an excellent market for reprogrammable non-volatile semiconductor technologies. Today’s single-chip, Flash-based mixed-signal FPGAs offer integrated analog capabilities, Flash memory, FPGA fabric and, often, an embedded industry-standard microprocessor. As a result, they can perform the system, power and thermal management and control functions of clinical medical devices – from system power-down/-up functions and data logging to temperature and voltage sensing.
Flash-based mixed-signal FPGAs are uniquely suited to clinical medical applications because of their high levels of integration, intelligent power and system management capabilities, small footprint and high reliability. These advantages help clinical medical applications meet battery specifications, reduce design footprints, minimise heat dissipation and ensure reliable operation of these shrinking medical applications.
The mixed-signal FPGA enables several discrete components to be removed automatically from the system board and integrated into a single, highly reliable device. These include the Flash memory, pulse width modulator (PWM), discrete analog ICs, clock sources and realtime clocks. Because Flash -based FPGAs store their configuration information in on-chip Flash cells, no external configuration data needs to be loaded at system power-up, unlike SRAM-based FPGAs. Therefore, these Flash-based, mixed-signal FPGAs do not require separate system configuration components, such as EEPROMs or microcontrollers, to load device configuration data at every system power-up.
This reduces system costs, board space requirements, and increases security and system reliability for medical devices.
Accurately measuring the temperature and controlling power of the system can increase cost and increase the reliability of the machine, thereby increasing the life of the product and of the patient. The analog circuitry of today’s mixed-signal FPGAs allows these critical features to be easily integrated and implemented. Another suitable clinical application for mixed-signal FPGAs is robotic surgery. Set to become the new standard in surgical procedures, robotic surgery has substantially simplified complex procedures as well as dramatically reduced patient recovery time and overall cost. These technologies can use digital cameras to deliver high-resolution images and the depth perception that a surgeon needs to accurately perform minimally invasive surgery.
Imaging applications
Though some medical imaging applications remain tethered to the wall, ultrasound machines have benefited the most from the market’s trends toward miniaturisation and portability. Historically, ultrasound systems weighed hundreds of pounds and were large and expensive. In the past it was more practical to bring the bed-ridden patient, bed and all, to the ultrasound machine rather than vice versa. Only in the case of the critically ill patients who could not be moved was the ultrasound system manoeuvred, with difficulty, to the patient.
Over time, portable ultrasound technologies emerged, but achieving image quality on par with the larger devices proved to be a challenge, as was achieving the battery life, high-power computing, and efficient memory access that these applications require. High-quality handheld systems enable routine bedside scanning. This has not only improved patient access to safe, non-invasive diagnostic medicine, but has reduced the time and costs associated with such diagnostics. Flash-based, low-power and mixed-signal FPGAs can be utilised in data acquisition cards for filtering and data alignment, control cards, data consolidation cards for data buffering/FIFO and alignment as well as many system management and control functions.
Conclusion
Increasing healthcare costs, the prevalence of chronic diseases, and ageing populations are creating tremendous demand for affordable, accessible and reliable medical devices to improve global healthcare. In response, two trends have emerged for many types of medical devices: miniaturisation and portability. Today’s medical home-based, clinical and imaging devices are often very complex and highly use-specific. However, designers of today’s shrinking medical applications also face rapidly changing features and requirements as well as demand for complex functionality in a small footprint, low-power, high accuracy, and reliable operation, making flexibility, integration, and re-programmability paramount. As a result, the medical market is an excellent market for non-volatile programmable semiconductor technologies, such as Actel’s Flash-based mixed-signal and low-power FPGAs.
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