Taking advantage of opportunities and challenges in medical electronics

Key trends driving the medical electronics market are aging populations, rising health care costs around the globe, and the need for access to medical diagnosis and treatment in remote and emerging regions and in our own homes.

The different world economies will continue to drive trends in these areas and others for years to come. Consequently, some of the key concerns medical electronics manufacturers face today lie in the areas of portability and miniaturization, connectivity, safety, data security and quality, and reliability.

Power management
An important trend over the next decade will be the proliferation of portable medical electronics equipment. Making power management decisions early in the design cycle will help define system-level trade-offs that may be necessary to meet portability and runtime targets.

Smaller portable medical products may use disposable batteries, while larger systems might leverage various rechargeable battery chemistries and battery pack sizes. Features such as dynamic power path management (DPPM) permit the system to draw power independently of the battery charging path.

This allows a device with completely discharged batteries to be used as soon as it is plugged in, rather than waiting for the batteries to recharge. This could be life-saving in emergency situations.

Since battery voltages do not drop off in a linear fashion, voltage tracking alone will not give a true reading of battery life. Especially since the middle third of the voltage scale comprises 60 to 70 percent of the discharge cycle time.

Coulomb counting will not compensate for battery aging, so over time it "assumes" the state of the battery. Impedance tracking, however, allows the medical device to calculate the remaining runtime to within one percent error over the entire life of the battery. This is often accomplished by integrating a voltage translation to extract individual cell voltages and charge/discharge current.

Additional protection in portable power solutions includes cell overvoltage, undervoltage, over current and short circuit protection. System reliability is critical in medical electronics, so battery authentication is a key requirement.

In some battery management products a single-wire, bi-directional communication system can be used to link a 96bit device ID; device-unique 16bit seed; and a 16bit device specific CRC to provide security. This is an effective means of validating that the battery in use meets the OEM's requirements.

Using an incorrect battery pack can impact system runtime and damage the system, or even cause harm. An appropriate power management approach enables portability and makes it affordable by delivering both increased battery life and safety.

Miniaturization, integration
Ultrasound is a medical imaging market segment seeing high levels of innovation in portable equipment. Manufacturers of today's advanced portable or handheld ultrasound systems require highly integrated, scalable solutions.

This allows medical professionals to move beyond the lab or office to reach clients in remote settings or emergency situations around the world. Integration continues to enable this trend of portability, as well as cost savings. A good example of this is illustrated in the ultrasound imaging space (Figure 1 below).

Figure 1: Shown is a portable ultrasound system block diagram.

While efficiently maximizing memory usage and power consumption, embedded processors play a key role in balancing computational power, flexibility, battery life and system size in medical imaging devices.

For example, today's high-performance DSPs have enough horsepower to efficiently tackle the back-end digital processing on an ultrasound system. At the same time, the DSP's programmability provides the ability to implement the newest software algorithms available without changing system hardware.

OEM development teams benefit from increased system performance and reduced time-to-market provided by the high level of system integration found on DSP SoCs. By providing the right mix of DSP processing, general purpose control, dedicated peripherals, and optimized image and video compression, these SoCs provide a cost-efficient, low-power, single-package solution.

This allows developers to reduce board space and design time, letting them focus more of their efforts on developing differentiated products.

In addition to continued integration of embedded processing technology enabling ultrasound portability, integrating the analog signal chain is key. On the analog receive side of the signal chain, a single integrated analog front end (AFE) can displace the discrete multiple-channel LNA, VCA, PGA, low-pass filter and high-speed A/ D functions, providing LVDS data outputs.

By reducing the system's device count, an integrated AFE can decrease power consumption by up to 20 percent, offer a 40 percent lower noise figure and save 40 percent on board space.

Thus, saving significant system cost as a result. Integrated AFEs achieve levels of image performance suitable for ultrasound systems of all sizes, from handheld to high-end.

Expect to see hardware and software tool kits built specifically to leverage these technologies. This is an exciting time for medical imaging technology because with integration such as this, coupled with system level tool kits; it is poised to evolve at a faster rate than ever before.