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RFID Can Simplify Maintenance of Patient-Monitoring Devices

If medical equipment manufacturers integrate dual-interface RFID chips into the devices they make, hospitals could use the technology to communicate with those devices, access maintenance records and alerts, and upgrade software.
By Thomas Lavallee
Depending on memory requirements, these dual-interface memory chips may be multi-banked using one compliant I²C bus, and share the same antenna. Not only does this solution expand the memory possibilities, but the designer can take advantage of the 32-bit password security in all or part of any of the devices, thus granting conditional access.

M24LR64 Dual-interface RFID EEPROM

By now, you are probably asking, What happens if the device receives system commands at the same time I want to read or write something via RFID? As most engineers know, designing a simple system usually moves the complexity into the device. STMicroelectronics' M24LR64-R dual-interface EEPROM memory chip, for example, has built-in circuitry able to handle possible concurrent communications and powering activities from the RF and I²C sides.

Design Standards for Monitoring Equipment
Design standards for patient-monitoring equipment are a complex matrix, with dependencies on which patients are being monitored, and where this occurs. As mentioned earlier, evolving technology and standards present issues requiring the close tracking of manufacturing and maintenance data. Another difficult area to deal with is counterfeit accessories, sensors and other patient-monitoring apparatus. For attachments that plug in directly, it is possible to include some method of encryption that can be read by the host, which of course applies only to smart sensors and the like. For disposable attachments, the designer might want to include a low-cost RFID reader capable of interrogating an RFID tag embedded in the mating fitting. A secure challenge code could then be programmed into the dual-interface RFID chip.

As new accessories become available, it is a simple task to add challenge codes to the monitor. Counterfeiting is a growing and serious issue that requires a low-cost and reliable solution such as this.

ISO, Interoperability and Safety
Current dual-interface RFID chips employ the ISO/IEC 18000-3 mode 1 air-interface protocol (based on the ISO 15693 standard) that operates in the 13.56 MHz band. This standard, which supports up to a 1-meter (3.3-foot) range, depending on antenna size and other factors, is currently in use throughout the world. What's more, it operates at low levels of energy considered to be very safe, and has readers available in many configurations. Recently, we have seen interrogators entering the market in cell phones with software support for Android.

Designer challenges are not getting any easier. Fortunately, the options presently available offer a myriad of solutions, sometimes targeted at non-related industries. This type of system appears to be finding a growing number of applications in the medical market, as designers recognize the simplicity and capability to solve a series of troublesome details in one low-cost, low-power and easy-to-implement device.

Tom Lavallee is an STMicroelectronics senior principal engineer focused solely on the medical and health-care market in Southern California. He has been with ST for 26 years, holds a degree in electrical engineering and has worked in the company's automotive, consumer, computer and strategic segments.

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