Fujitsu Electronics

Fujitsu Semiconductor: High-speed FRAM-Memory Chips for High-Tech RFID Applications

Articles | By Fujitsu Electronics | 20 November 2014
Due to their resistance against radiation, FRAM-memory chips are perfectly suited for RFID-applications in the medical field. Due to their resistance against radiation, FRAM-memory chips are perfectly suited for RFID-applications in the medical field. Photo: Fujitsu Semiconductor

Data saved at high speed and permanently available

High writing speed and multiple billion overwriting cycles – only two of the various advantages that are brought by FRAM-technology and that qualify it as the ideal memory technology for many different RFID-applications. What particular benefits FRAM-technology has got for RFID-applications and where the boundaries of permanent data saving are, that’s what „RFID im Blick“ talked about with Jozsef Miho, product marketing engineer at Fujitsu Semiconductor Europe.

Jozsef Miho, Fujitsu Semiconductor Europe, in an Interview with Jan Phillip Denkers, „RFID im Blick“

Mr. Miho, what are the main differences between FRAM and other types of RAM?

Compared to SRAM and DRAM that are produced in CMOS-processes, FRAM is based on a special capacitor technology that needs a certain manufacturing process. That process is based on CMOS-technology. These capacitors are not based on the charging of electrodes, but use ferroelectric material between the electrodes. When creating an electric field, polarization is formed. This polarization still remains if the power supply, and thus the electric field are removed. So, the permanent saving of data is possible – the deciding difference to volatile memory technologies.

Fujitsu Semiconductor Europe manufactures FRAM components with different memory capacities. Where are the boundaries regarding the memory size?

The standalone FRAM-memory chips that are available at the market have got a capacitiy of up to four Mbit. The biggest planned FRAMs on our roadmap are of 16 Mbit.

Depolarization and imprint can also cause data loss at FRAM, especially when exposed to high temperatures. How does Fujitsu Semiconductor Europe assure a permanent data storage?

It is true that imprint and depolarization lead to data loss, but that is harmless in most applications where FRAM-memory is in use. Fujitsu states that for nearly all FRAM-products a safe data retention of ten years at an operating temperature of 85 degree Celsius can be guaranteed. That means that in the worst case scenario of permanent use at 85 degrees Celsius over a period of ten years, and without access to the data, the saved information still remained available. If the temperature was not permanently that high, or the content of the memory cell was “refreshed” by a read- or write access, the time respectively extends.

The temperature curve is relatively steep: For example, at permanent 55 degree Celsius, the data retention is at the range of 95 years, it’s over 200 years at room temperature. There should be very few applications where this retention is not sufficient. However, we are of course steadily improving our products. First, products now have specifications of ten years at 105 degree Celsius and further improvements are already planned. Also, depending on the application, with the targeted use of circuits in module design, the characteristics of FRAM in this aspect can be improved.

What are the (main-) benefits of FRAM compared to other non-volatile types of RAM such as MRAM?

Generally speaking: Every user has to identify the right technology for his application, because all non-volatile memory technologies have certain advantages and disadvantages. Compared to EEPROM, the advantages of FRAM are obvious: The reading speed of FRAM is many times over, especially when directly accessing. The number of overwriting cycles is around one million at EEPROM. FRAM is about a factor of ten million higher, ie 10 to the power of 13. The energy consumption at FRAM, in particular when writing, is a fraction of what is needed by EEPROMs. Since FRAM is not based on charging but on polarization of ferroelectric material, it is resistant against radiation. This is of high importance, particularly in applications in the medical sector, due to the high radiation doses needed for sterilization. Also, in applications that are regularly exposed to radiation, such as baggage handling systems at airports, data in EEPROMs may be distorted.

MRAMs have in contradiction to FRAM, also higher energy consumption and can be influenced by strong magnet fields. On top of that, MRAM is not available in small memory sizes because the technology is hardly scalable. Therefore, there are only MRAMs available with memory sizes of 256 kBit and more, what may be, depending on the application, totally oversized for the intended use. The fact that MRAM is a single supplier technology is surely in the eyes of some market participants another disadvantage.

What RAM-type is best suited for the use in RFID transponders?

RAM or EEPROM memory technology is in use in almost all RFID-transponders. Both technologies are not considered to be competitors since FRAM-transponders usually have significantly bigger memory sizes than transponders with EEPROMs. The latter is often not equipped with user memory, but only saves an ID, depending on the transponder frequency, in form of an EPC (UHF) or an UID (HF). Big memories with EEPROMs are unpractical since a transponder would need to stay in the field of the reader for a long time, whereas reading times at an access of transponders with FRAM are way faster.

Minimum size becomes a decisive factor when developing transponders, in particular for surgical instruments. What limits are set by the size of FRAM-components?

Regularly, Silicon is directly integrated into tags. There are small transponders that don’t need “so-called” modules except for where the antenna is directly bonded onto the silicon. The smallest air coils, I know of, are three millimeters in diameter.

FRAM is due to a technical characteristic – resistance against radiation – suitable for the usage in the medical sector, however, its temperature resistance is limited. How can RFID-transponders with FRAM nevertheless be employed process reliably?

The temperature resistance is principally no problem, except at applications with permanent extreme temperature ranges. Accelerating aging test with high temperatures, we determine retention times. Right now, these test are at around 150 degree Celsius and last, depending on the product, up to a few thousand hours. Short infringements over the temperature specified should – even though it is not specified – cause no problem. In the medical field, for example in conclaves, the items that have to be sterilized are usually exposed to temperatures of 120 to 130 degree Celsius for around 30 minutes. An FRAM-tag can almost certainly endure these temperatures occasionally, even though it is not specified, since the tag is exposed to even higher temperatures in our tags. Of course, the transponder should not be permanently stored in a conclave – at least when there is an importance attached to permanent data retention.

Apart from medicine: In what other applications can FRAM-technology lavage its strengths compared to EEPROM or other NVRAMs?

In particular, in the industrial sector when a big quantity of data has to be accessed quickly, or in logistics processes that profit from high speeds, as well as from big memory, FRAM-tags are in use. Also, at the capture of movable objects, for example in toll tracking, applications benefit from high writing speeds. In the field of stand-alone devices, thus not in the RFID-field, FRAM plays a big role at metering applications (gas-, water-, electricity meters).To sum it up, it is of high importance in applications where high writing speeds, either for reasons of data throughput, or for safety reasons, a high number of overwriting actions and at battery-run applications, a low energy consumption is crucial. Furthermore, when using FRAMs, PCB-space can be reduced when removing other quicker SRAMs, because they are not needed anymore. A reduction of effort and costs will also be the result when batteries can be omitted.

Last modified on Monday, 02 March 2015 10:15