Trend Analysis: FRAM in the Medical Field - Fujitsu Semiconductor
FRAM, the Advanced Memory
Creating Added Value for Medical Devices
FRAM from Fujitsu Semiconductor Limited is gaining spotlights in the medical field with wider applications and adoptions. FRAM offers numerous unbeatable advantages, including fast write, great read/write cycles, low power consumption and radiation tolerance, adding new values to medical equipment and systems. FRAM is already used in CT scanners and other large equipment, and increasingly in smaller medical devices too. RFID containing FRAM is also becoming more widespread for authentication purposes in medical devices and control in biopharmaceutical manufacturing.
FRAM (Ferroelectric Random Access Memory) is a non-volatile ferroelectric memory which uses ferroelectric film to preserve data. It incorporates both non-volatile, and random access, properties, preserving stored data for extended period even if power to the chip is turned off.
Various new types of memories have come onto the market in the past few years, such as MRAM (magnetoresistive random access memory), which uses magnetic material for the memory cell; PRAM (phase change random access memory), whose memory cells are made from heat-sensitive material; and ReRAM (resistance random access memory), which has memory cells made from material whose resistance value changes according to the applied voltage. Proven track record for supplying to mass market for more than a decade is what sets FRAM a class apart.
Mass production of FRAM began in 1999. FRAM is highly reliable and is used mainly for industrial applications, in factory automation equipment, measuring equipment, power meters, bank terminals and so forth. FRAM incorporates several superior properties not found in conventional standard non-volatile memories as described above, creates added values for medical systems and devices (Figure 1).
Figure 2. Comparison between standard EEPROM and FRAM
Compared to conventional non-volatile memories, FRAM consumes significantly less power and have higher write speed. FRAM uses less than 1/100th the power of EEPROM for comparable writing. FRAM's write speed of 1/40,000th comparing to that of EEPROM is on par with conventional volatile memories like SRAM and DRAM (Figure 2). Furthermore, FRAM has great performance in read/write cycles compared to EEPROM and flash memories. Whereas EEPROM and flash memories can be written up to one million times (106 times), FRAM can be written 1012 times, or one million-fold more.
An additional feature of FRAM is that the ferrocapacitor using polarization to preserve data is less vulnerable to data loss due to radiation exposure. In the case of EEPROM and flash memories, which preserve data depending on whether an electrical charge is present in the storage area of the element, exposure to radiation causes the electrical charge to shift, writing the data, resulting in data corruption. But FRAM, which stores data through polarization of the material, is less affected by radiation.
Figure 3. Small 8-pin SON package
Another important feature of FRAM is the device's excellent security. In memory devices such as EEPROM, which use a floating gate structure, changes in the electrical charge can be detected, allowing the stored data to be read by third parties. FRAM, which record data based on the direction of polarization, are less exposed to this risk.
Backed by the matured technology for producing FRAM for more than a decade, Fujitsu Semiconductor offers a wide product lineup which includes stand-alone FRAM, and dedicated LSI such as RFID (radio frequency identification) ICs, authentication ICs and other products incorporating FRAM. Among these, stand-alone FRAM and RFID are used in the medical industry. Stand-alone FRAM density ranges from 4K bits to 4M bits products with three interfaces: SPI (Serial Peripheral Interface), I2C and parallel. The product range includes a device in an ultra-small package of 2mm × 3mm (Figure 3). The RFID ICs come in a package integrating wireless communication circuits and FRAM embedded in RFID tags or IC cards, available with 256 bytes to 9K bytes FRAM on the HF band (13.56 MHz) and 4K bytes to 64K bytes FRAM on the UHF (860 MHz–960 MHz) band.
Below are some examples of the advantages that FRAM features offer for medical applications.
FRAM in CT Scanners: No Battery Replacement
Mr. KajimotoMarketing Dept.System Memory Div.
The CT scanner is one type of medical equipment using FRAM, which several equipment makers began adopting three or four years ago. Depending on the maker, FRAM is used for different purposes inside the equipment, one of which is a control system for determining when the equipment requires maintenance.
The performance of cameras and X-ray generators inside CT scanners deteriorates with repeated use and such components must be replaced regularly. This is where FRAM comes in, where it is used as the memory device for the control system to record hours of operation and radiation exposure amounts. FRAM chip is well suited in this stringent operating environment thanks to its fast write, great read/write cycles and radiation resistance properties as a non-volatile memory.
Until now, control systems for CT scanners often used SRAM chips, which are capable of fast write. But according to Kazuki Kajimoto, Marketing Department, System Memory Division, MCU Solutions Business Unit, Fujitsu Semiconductor Limited, "SRAM needs a battery in order to preserve data, and this battery needed to be replaced at regular intervals. Using FRAM instead of SRAM eliminates the need for a battery, thus reduces maintenance and prevents failure due to drained battery."
FRAM for Bio-information Monitoring: More Detailed Information on Vital Signs
Mr. TomiokaMarketiong Dept.System Memory Div.
FRAM are also used in bedside monitors recording or monitoring patients' vital signs—heart rhythm, pulse, blood pressure, body temperature and so forth. These monitors contain patients' pre-recorded benchmark information and comparing against the most recent measured data. An alarm sounds if abnormality is detected. FRAM is used in these systems' storage medium. Regarding this application, Ken Tomioka, Marketing Department, System Memory Division, MCU Solutions Business Unit, Fujitsu Semiconductor Limited, says, "FRAM, can be written more often as compared to EEPROM, the equipment can take measurements more often, which allows the monitors to record information in greater details. FRAM's fast write capability also means that no data is lost if there is a sudden power outage, because the FRAM can store data in the shortest time before power to the system is interrupted."
FRAM for Auto-CPAP: Battery-free
FRAM is also being considered for use in auto-CPAP (continuous positive airway pressure) devices used to treat sleep apnea. CPAP monitors and records data on the patient's breathing during sleep and assists breathing as needed. "Auto-CPAP currently uses SRAM for storing data, but using FRAM instead would eliminate the need for the battery needed to preserve data on the SRAM." says Mr. Kajimoto, "Some CPAP use an EEPROM to store the device's initial parameters, but using the FRAM for storing those parameters as well as recording data would eliminate the need for an EEPROM too."
FRAM in Hearing Aids: Noise Control
Some hearing aid makers are considering using FRAM in hearing aids. Many hearing aids nowadays can be adjusted for optimum performance according to individual usage conditions. They incorporate a recording system for logging this information, and FRAM is being considered for use as the recording memory. Hearing aids currently often use EEPROM to record information, but FRAM, which can write data more quickly, also consumes less power. For example, when writing 64 bytes of data at the same frequency, FRAM can write 20 times faster than EEPROM while consuming only 1/140th the power, meaning less frequent battery replacement.
FRAM offers another unique advantage, namely reducing noise that occurs when data is written in the memory. With EEPROM, about 10V high supply voltage is internally required to erase and write data into memory. This high supply voltage at writing creates noise in the circuitry, which translates to audible irritating noise to the hearing aid user. With FRAM, which does not need high voltage to erase and data, this problem can be eliminated.
FRAM to Control Medical Devices, Products and Pharmaceuticals: Sterilization by Radiation Offers Improved Convenience
Mr. TeramaeSolution Engineering Dept.System Memory Div.
FRAM has been contributing to the growth of the medical field not just as a stand-alone component but also through the use of RFID ICs with FRAM. For example, RFID tags can be used to control and authenticate medical devices, products and pharmaceuticals. Several RFID tag makers and systems manufacturers have commercialized RFID tags with FRAM for the medical field, which have been put into use in medical devices and bio-pharmaceuticals.
RFID tags can read and write information into their internal memory over wireless networks. Not only can RFID record vastly more information than bar codes, the information can also be written continuously, so RFID tags are often used for tracing systems and other applications in the logistics and manufacturing fields. But there was one area in the medical field where RFID could not be used up to now is the tagged item which is sterilized by radiation.
Medical devices which must meet especially stringent sanitary standards are often sterilized using special gases or by other methods, but sterilization by radiation is widely used for single-use medical devices and for parts in bio-pharmaceutical manufacturing equipment. Sterilization by radiation is used because it causes fewer environmental problems and because already packaged items can be sterilized minimizing possible contamination from further processing after sterilization. End users have complained that radiation can cause the data on RFID tags with EEPROM to be lost, so the tags can no longer function as identifiers. Using FRAM on the RFID would eliminate this problem.
Today, standard memory device such as EEPROM and SRAM are widely used in medical equipment. Using FRAM is likely to remedy a frequent source of complaints by ordinary end users and medical professionals about hearing aid noise or the need to change batteries in the equipment they use. FRAM products help collect more detailed data and heighten data reliability, and can also contribute to improving safety and boosting productivity in medical industry.
Fujitsu Semiconductor intends to develop more FRAM products not only for the medical sector but to meet new needs as well, so it's a good idea to keep an eye out for future products from the company.
[Interviewed by Nikkei Business Publications, Inc. (November 2012)]
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