Medical Device Link.

Originally Published MEM Fall 2004

DISPLAY TECHNOLOGY

Christophe Chene

From the user's perspective, the display is usually the most important component of a medical instrument. But inside the box is the real brain of the device—the microprocessor. As medical equipment and other appliances have evolved toward greater portability, more and more functions are being integrated onto the microprocessor chip. The result of this development is system-on-chip (SoC) devices consisting of a microprocessor and various peripherals integrated on a single chip. The purpose of SoCs is to optimize power and performance at a low cost.

Selecting which SoC to use in a portable medical device is a critical design step. Here are seven factors for engineers to consider on the way to arriving at the best choice.

SoC and LCD Controller Integration

When choosing an SoC for an application that incorporates a liquid-crystal display (LCD), the design engineer should consider SoCs that include an on-chip LCD controller. The engineer should select an SoC that can drive a display with minimal circuitry. Also, programming should be straight-forward and flexible enough to support a variety of display options. Integrating an LCD controller with the SoC minimizes the cost and complexity associated with the need for additional logic to drive the LCD, while optimizing overall system performance.

Onboard Network Connectivity

The engineer should consider whether the SoC integrates on-chip capabilities for network and/or external connectivity. This capability has become a de facto requirement for portable medical devices, as medical practitioners need to share information in real time with other systems. Some SoC manufacturers offer on-chip networking capability via Ethernet, USB, and other communications protocols.

Cost versus Performance

Some SoCs are optimized for portable applications. These components feature power-saving hardware and one or more sleep modes to minimize power consumption. The design engineer should look for an SoC that balances the right amount of processing power and on-chip peripherals to provide optimal performance within the power budget. For example, SoCs with ARM7 or ARM9 cores offer low-voltage operation to minimize power consumption.

Hardware and Software Development Tools

The right quality and variety of development tools can save both time and money in a design project, and thus accelerate market introduction and benefit the corporate bottom line. So it is important to look at the tools available for the SoCs being considered for the application.

If an objective is a faster time to market, one new approach is especially worth investigating. This approach uses a modular card engine, which is a small production-ready single-board computer that can readily become the actual hardware component in the completed product. Using an already-proven design facilitates the transfer from a development system to the operating hardware and eliminates the core processor-board design effort. The card engine architecture also provides scalability for future products. Further, the modular design enhances the possibility of reusing code modules and more-powerful future processors.

Industry-Standard Architecture

Use of a mainstream architecture, such as ARM, in the SoC minimizes implementation time by providing the engineer with access to a large base of software libraries from multiple providers. Additionally, use of a standard architecture helps the design engineer maximize code reuse and migration from one platform to another, improving the likelihood that the same design can be leveraged for future products.

Suitability for a Small Handheld Format

The engineer should evaluate each SoC to determine whether it is designed to operate small-format handheld devices optimally. There are many SoCs to choose from, but only a select few are designed specifically for small portable devices. SoCs designed for handheld devices generally integrate on the same chip many components commonly required for portable operation, including USB ports, UARTs, general-purpose input/output, timers, SmartCard, MultiMediaCard, and other interfaces. Some SoCs incorporate a touch screen controller as well, for enhanced ease of use.

System Solutions

Finally, the design engineer should look for SoC manufacturers that provide total system solutions. Up-front integration of the SoC to a high-quality LCD display, flash memory, optoelectronic devices, and other key design components such as a touch screen can assure the engineer that development time and the bill of materials will be kept to a minimum.

This integration of features is essential in portable medical device design today. It enables engineers to efficiently develop and bring to market products that meet the diverse and ever-changing needs of medical practitioners worldwide.

Christophe Chene is senior director of IC marketing for Sharp Microelectronics of the Americas (Camas, WA). He can be reached at 360-834-2500.

Copyright ©2004 Medical Electronics Manufacturing