Monday, July 14, 2014

Getting An Edge With FRAM MCUs: Transportation, Data Loggers And Remote Sensing

As mentioned in yesterday's post, today I'm taking a look at applications ideally suited for the advantages FRAM (ferroelectric random access memory) gives microcontrollers (MCUs) compared to SRAM (static random access memory) and flash memory.

The Electronics Weekly article, "Embedded FRAM opens up MCU design," focuses on why monitoring the shipment of sensitive items is an ideal application for MCUs with FRAM. We'll take a look at why the author thinks transportation is a killer application for FRAM MCUs. He reviews technical and performance advantages FRAM has in MCUs over the other memory types. At the end of this post, I'll mention a couple other applications where FRAM MCUs have significant advantages over MCUs without FRAM.

Medicines, food and other temperature sensitive products can be ruined or degraded if they get too hot or too cold during shipping. Sensitive technology equipment, and other types of high-cost fragile equipment can be unknowingly damaged if their transportation conditions aren't monitored and recorded. Electronics Weekly sums it up the current state of monitoring and recording sensitive transportation conditions this way:
"Currently, chemical or mechanical indicators like liquid contact indicators, humidity stripes, chassis intrusion indicators or predetermined breaking points are used to detect mechanical overloads. These sensors are able to detect the incident itself even if the device is in transit and no grid power is applied. However, these methods provide no information about date, time or location where the incident happened...electrical sensors are already used to track certain data types, such as temperature, usually through battery-supplied stand-alone data logging systems. But only a limited amount of sensor data can be recorded when the device is on storage or transport, without access to power from the’s available standard storage technologies – like flash and EEPROM – are limited in terms of write cycles...and the high power consumption..."
Specific technical advantages of FRAM are that it's non-volatile and very little energy is needed to write to a FRAM memory cell compared to a flash memory cell. As the article linked above explains it:
"FRAM is a non-volatile memory technology...FRAM cells...use a 70nm ferroelectric crystal layer as the dielectric material to store its refresh cycles are required and stored information is retained when switching off the supply voltage...Only 1.5V programming voltage is required to perform writes to the memory since the ferroelectric crystal layer has a thickness of 70nm...logged data can be overwritten an almost infinite amount of times. Current datasheet values are around 1015 write cycles, compared to flash which offers up to 107 write cycles...the energy consumption for programming an FRAM memory cell is about 250 times smaller than of a current low power flash cell...Accurate time stamps can be stored in addition to every single measurement value...With FRAM built into an ultra low power microcontroller system, data can also be recorded with the data logging system only supplied by a very small battery...A complete picture of a products life cycle can be recorded with this technology at a level of detail that was impossible to obtain in the past."
Finally, using FRAM allows MCUs to be designed more efficiently for applications that need significant amounts of RAM. An EE Catalog article explains it this way:
Comparison chart for FRAM vs other MCU memory types
"In a traditional microcontroller, SRAM and flash sizes typically scale larger together. RAM-intensive applications usually require a microcontroller that has both a large amount of SRAM and flash, causing a large chunk of flash to go to waste. Wasted flash is a severe drawback as it increases the physical size of the die as well as the cost. These large memory devices are also larger in size with a higher pin count. Many applications need a large amount of data memory without the additional scaling of other aspects of the microcontroller...FRAM enables flexibility of design by no longer restricting memory options to the small sample of predetermined RAM and flash sizes of traditional microcontrollers."
It's probable that five years from now, most highly sensitive shipments will use embedded FRAM MCUs to monitor and record data such as temperature, mechanical shock and more, and each measurement will have an accompanying location and timestamp.

Improved tracking of transport condition will result in several benefits:
  1. Shipping companies will improve shipping conditions because they don't want to be held accountable for damages and because they have data that identifies exactly when and where damage occurs.
  2. Companies that ship sensitive goods will have decreased losses during shipping, many fewer shipments that are damaged but not known to be damaged, and happier customers.
  3. Production volume of FRAM MCUs and associated embedded components will increase dramatically, lowering the unit cost to manufacture these components and providing revenue to fund more innovations to improve this technology.
data logger
Other applications highly suited to the non-volatility and low write-energy of FRAM are data loggers, remote sensors and equipment powered by energy harvesting. Data loggers often need large volumes of data recorded and sometimes need it recorded quickly. The speed of writing to FRAM and it's extremely low write-energy make FRAM MCUs ideal for data loggers. Battery powered remote sensors with FRAM MCUs reduce field maintenance costs by extending the battery life. Energy harvesting power is not as steady or reliable as conventional wired or battery power. FRAM MCU systems will safely store data, even if the power supply has an occasional outage.

For more background on applications for embedded FRAM MCUs and FRAM technology, check out the Texas Instruments FRAM applications webpage, a Fujitsu PDF, FRAM MCU Key Strengths and Applications, and the 'FRAM MCUs For Dummies' article on (source of the FRAM memory comparison chart above on left).


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