Trends in memories for medical electronics show promise to enhance and extend life. (Special Report: Components for Medical Electronics).
One of the components behind the revolution of medical instrumentation is low-power MOS memory. These advanced memory products are the result of rapid innovation driven by the huge demand for lower power and larger memory for the cellular phone market. A good example of these innovative products is the so-called IT-based (one transistor) pseudo SRAM (PSRAM). Mostly a DRAM in SRAM clothing, these devices make low cost DRAM technology available to a wide variety of applications that could not consider a DRAM before. These chips are among the most sophisticated memory chips in the world. There is no need to worry about DRAM refresh, CAS and RAS, and all the other complications of DRAMs -- an address is put in and data comes out. Data is stored and it stays there without further intervention as long as power is maintained. These products also serve to make battery backup more achievable by using far less power in both active and standby modes than the best memory chips of just two years ago.
Many portable medical instruments such as blood glucose measuring devices, halter monitors (portable EKG recorders) and insulin-dispensing modules can take great advantage of the new, low-power memory devices. Halter monitors can now eliminate bulky and unreliable tape recording devices and store information in devices such as the PSRAMs described previously. However, some of these applications may require even lower power than is obtainable from these advanced PSRAMs. For example, if one expects to maintain data in the memory for extended periods when the main battery is removed, it may be necessary to retain data for days or even weeks on a small back-up battery. In such cases, the more traditional 6T SRAM is the answer. Even the 6T SRAMs have improved well beyond where they were a few years ago. NanoAmp Solutions and other SRAM vendors utilize the latest in process and circuit technology to supply 6T memory with much less than 1 [micro]A standby current. Some products, such as the NanoAmp N01L1618N1A, can retain data for in excess of 100,000 years on the energy available in a single flashlight battery.
Probably the most challenging medical electronics product in production today is the implantable defibrillator. These products require sophisticated microcomputers and a substantial amount of memory in each module. At the same time, such implanted products must sustain operation full time for a minimum of five or more years with no opportunity to recharge or replace the battery. Memories in these applications go to great lengths to minimize power but can get to the point where power required to drive the interface between the memory and the microcomputer consumes a significant amount of the available energy. In such cases, the obvious step is to combine the memory and microcomputer on the same chip, thus eliminating the interface current. The main difficulty here is finding a supplier with sophisticated low-power memory technology that is willing to do an ASIC for a relatively low-volume customer.
There is a real surge in creative electronic applications occurring today that will enhance and sustain life for a great many people. Fortunately, existing technology used in applications, such as cellular telephones with their huge purchasing power, are driving semiconductor technology to keep pace with the needs of the medical market.
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Mike McCoy is vice president of marketing, medical products for NanoAmp Solutions, Inc. (www.nanoamp.com), San Jose, CA. He can be reached at (408) 573-8878; firstname.lastname@example.org.
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|Publication:||ECN-Electronic Component News|
|Date:||Nov 15, 2002|
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