Understanding FRAM Technology
Introduction
Ferroelectric Random Access Memory (FRAM), also known as FeRAM or F-RAM, is a memory
technology that combines the best of Flash and SRAM. It is non-volatile like Flash, but offers
fast and low power writes, write endurance of 1015 cycles, code and data security that is less
vulnerable to attackers than Flash/EEPROM, resistance to radiation and electromagnetic fields,
and unmatched flexibility. This memory technology has been around for decades, but is now
being integrated in MSP430 ultra-low-power microcontrollers (MCUs) to bring its unique
advantages to real-world applications.
Molecular Structure
FRAM is a random access memory, meaning that each bit is read and written individually. This
non-volatile memory is similar in structure to DRAM, which uses one transistor and one
capacitor (1T-1C), but FRAM stores data as a polarization of a ferroelectric material (LeadZirkonate-Titanate). As an electric field is applied, dipoles shift in a crystalline structure to store
information. This structure results in a number of advantages:
Non-volatility
Fast writes
Low power
High endurance
Resistance to electromagnetic fields and radiation
Unmatched flexibility
Data Security
The use of crystal polarization as opposed to charge storage enables state retention, lower voltage
requirements (as low as 1.5V) and fast write speeds when compared against Flash, EEPROM and
SRAM technologies used in typical MSP430 microcontroller applications. In addition to benefits
associated with traditional memory technologies, FRAM offers system level security
advantages. The lack of a charge pump removes a key vulnerability against physical attacks.
FRAM is also resistant to electric/magnetic fields as well as radiation. Since FRAM state is not
stored as a charge, alpha particles are not likely to cause bits to flip and the FRAM Soft Error
Rate (SER) is below detectable limits. On top of this resistance to external interference, FRAM
is anti-tearing, meaning power lost during a write/erase cycle will not cause data corruption.
Finally, data can often be protected using encryption. The fast write speed and high endurance of
FRAM enables developers to generate keys more frequently to better secure data transmission.
Technology Comparison
The previous section described some of the advantages of FRAM, but does FRAM really stackup well against traditional forms of memory technologies? The answer is yes! The table below
will summarize the key advantages of FRAM when compared against Flash, EEPROM, and
SRAM.
All-in-one: FRAM MCU delievers max benefits
Specifications
FRAM
SRAM
EEPROM
Non-volatile
Yes
No
Yes
Retains data w/o power
Write speed
<10ms
<10ms
2 secs
(13 KB)
Average active Power
[A/MHz]
100
<60
50,000+
16 bit word access by the
CPU
Write endurance
1015
Unlimited 100,000
Flash
Yes
1 sec
230
10,000
All-in-one: FRAM MCU delievers max benefits
Specifications
FRAM
SRAM
EEPROM Flash
Soft Errors
Below Measurable Limits
Yes
Yes
Yes
Bit-wise programmable
Yes
Yes
No
No
Unified Memory
Flexible code and data
Yes
No
No
No
partitioning
* Based on devices from Texas Instruments
FRAM Use-Cases
FRAM technology offers several advantages over traditional memory technologies. These
advantages can lead to real function-level benefits in low-power applications.
EEPROM replacement
Low-energy backup on power fail
Over-the-air updates
Remote sensing or data logging
Energy harvesting
Data security
Development flexibility
Manufacturing efficiency
EEPROM Replacement - Low power and high endurance means external EEPROM may be
unnecessary
Solution Features
Lower energy
Not limited by I2C protocol speed
1 billion times more write erase cycles than EEPROM
Bit-wise programmable
Increased memory size options
Solution Benefits
System is faster and more efficient
Can write more data over the same system lifetime for more data accuracy or
can extend the system lifetime
FRAM is flexible and easy to use
FRAM-based MCUs can scale easily with your design
Low energy backup on power fail - FRAM enables data backup when power is lost
Solution Features
FRAM writes consume 250x less energy per bit than Flash
FRAM writes use the same power as reads and there are no spikes in peak
current because of the lack of a charge pump
FRAM on MSP430 MCUs has built-in circuitry to complete the current 4 word
write (integrated LDO and capacitor)
Solution Benefits
10x the backup capacity
o
Consider a battery source depleting by 0.2V every 0.01 second. In the
ideal case w/o erases and discounting the peak current hit, about 8K
flash bytes can be written, in comparison the FRAM equivalent is 80K
bytes allowing the user complete flexibility to plan and execute a full
fledged backup subroutine w/o having to worry about the impending
power loss
Over-the-Air Updates - Speed of FRAM writes can make over the air updates more reliable
Solution Features
Updating FRAM takes 100x less time and 250x less energy/bit
No pre-erase required
Data can be written on-the-fly
o
Data can be written to FRAM right out of the COMM channel, with no
buffering required
Hardware accelerators for encryption/decryption using the Advanced
Encryption Standard (AES)
Solution Benefits
Battery life extended by limiting active radio time
FRAM simplifies development
Data secure on power loss, making verification algorithms simpler
AES paired with authentication can prevent exploitation
Remote Sensing or Data Logging - Extend product life and reduce maintenance
Solution Features
Lower energy
o
Fast writes
Low voltage and current is needed to change FRAM data
Near infinite endurance
o
10 billion times more cycles than Flash
Solution Benefits
Go longer without replacing batteries
o
Install cost can be much greater than battery cost
FRAM MCU can save an extra voltage supply and reduce peak system
current
Low voltage and current is needed to change FRAM data
High endurance means:
o
Higher accuracy - more samples can be taken over the same product
lifetime
Extend product lifetime - samples can be taken at the same frequency
for longer
FRAM MCU can save an extra voltage supply and reduce system peak current
o
Writes to the FRAM cell occur at low voltage and very little current is
needed to change the data
As a comparison, EEPROM high 10-14V may be needed
Field-Powered NFC for Access Control & Security Applications TI Design
Wireless Motor Condition Monitor TI Design
Energy Harvesting - Improve battery efficiency or remove them all together
Solution Features
Low active duty cycle for non-volatile writes
o
Faster wakeup time
o
Low average and peak write power leads to low average and peak
power consumption of the MCU
Variables stored in non-volatile FRAM
Perfect pair with BQ25570
o
Specifically designed to acquire and manage W to mW of power
generated from DC sources solar, thermal or wind
Solution Benefits
Achieve closer to rated battery capacity
o
battery efficiency is improved and lifetime is extended by limiting peak
current consumption
Energy harvesting can be the only source of energy, or can complement
batteries for longer product lifetime
Data Security Protect intellectual property and transmissions with FRAM
Solution Features
No charge pump needed
Resistance to external fields
State retention on power fail, fast writes and 10 write cycles
Hardware accelerators for encryption/decryption using the Advanced
Encryption Standard (AES)
Solution Benefits
Memory protected from some types of physical attacks
FRAM is not susceptible to Soft Errors
Update security keys quickly and send notifications in case of certain state
changes
AES paired with authentication enables more secure data communication
Development Flexibility - Eliminate traditional boundaries between code, variable and constant
data
Solution Features
Flash:RAM ratio is industry standard, no customization allowed!
o
FRAM breaks down this barrier with the ability to customize the size of
your memory blocks
Flexibility to change these boundaries at run-time or compile-time
Solution Benefits
Fewer platforms = quicker time to market
o
FRAM enables developers to maintain 1 platform across projects with
differing needs
Lower System Cost
o
No need to pay for a larger device just to get more RAM
Manufacturing Efficiency - Saving time = saving money
Solution Features
FRAM can be written at much greater than 1MBps
o
100x the write speed of Flash
Solution Benefits
Improve time through the manufacturing line for savings in high volume
production
FRAM Customer Testimonials
Engineers around the world are adding FRAM-based microcontrollers to their systems. Checkout some of the exciting applications from electronic shelf labels (ESLs) to asteroid mining
below:
Battery-powered sensors Providing objective data to aid in triage and medical
treatment of traumatic brain injuries
"Lower power = longer battery life
Customer Problem
Small form factor
Sustained functionality on battery power for extended periods of time
Need to collect data regularly
FRAM Advantage
Data stored quickly with minimal overall power
o
MSP430 ADCs can operate in low-power modes and store data directly
to FRAM without CPU intervention
Integrated FRAM and other system components on MSP430 microcontrollers
reduce overall system size
Product lifetime extended with 1015 write cycle endurance
Weather Monitoring Localized Wind, temperature and humidity information
available in real-time
"The FRAM series allows us to achieve ultra-low-power as well as simplifying data buffering in
our firmware
Customer Problem
Real-time data requirements can quickly exceed memory limits
Limited power sources available in remote location
FRAM Advantage
1015 write cycle endurance greatly exceeds that of other non-volatile memory
technologies
The ultra-low active and standby current of FRAM MCUs enable energy
harvesting solutions and extended battery life
Stadium Lighting Redefining the possibilities and power consumption
It was the FRAM in the device that was a deciding factor in the selection. As power
interruptions and inconsistent power cleanliness is a constant battle we needed to be able to
retain fundamental command and control code
Customer Problem
Power interruption present can create major due to long system startup times
Updating firmware across many nodes can be challenging
Thousands of lighting fixtures can lead to a large energy bill
FRAM Advantage
High write speed and endurance enable quick wakeup and immediate
restoration of state
Updating FRAM is simple and fast with no buffering or pre-erase requirements
Ultra-low standby current enables system management to meet energy
requirements
FRAMs as alternatives to flash memory in embedded
designs
Priya Thanigai, Texas Instruments
July 19, 2012
inShare2
Ferroelectric random access memory (FRAM) is widely known as a non-volatile, stand-alone
memory technology that has been a part of the semiconductor industry for more than a decade.
In recent years, integrated circuit manufacturers have been considering FRAM as a strong
contender for embedded, non-volatile memory, as an alternative to flash technology. This article
discusses key technology attributes of FRAM while exploring specific use cases that demonstrate
FRAMs advantages.
Today there are multiple memory technologies that have the potential to change the landscape of
embedded processing. However, none so far have surfaced as a strong contender for replacing
flash technology in microcontrollers (MCUs) until FRAM.
What is FRAM?
FRAM is non-volatile memory that has power, endurance and read/write speeds similar to
commonly used static RAM (SRAM). Information stored in an FRAM cell corresponds to the
state of polarization of a ferroelectric crystal that can hold its contents even after the power
source is removed. This is what makes FRAM truly non-volatile. Also, since the energy required
to polarize a crystal is relatively low when compared to programming a flash cell, FRAM writes
are inherently lower power than flash.
Click on image to enlarge.
Figure 1. FRAM allows for continuous ultra-low-power data logging and
supports more than 150,000 years of continuous data logging (vs. less
than 7 minutes with flash)
Here are a few typical applications that use microcontrollers with flash technology
today. Lets look at how leveraging FRAM-based MCUs, rather than flash-based
MCUs, bring cost, energy and efficiency optimization.
Data logging
A typical data logger application such as a temperature data logger can sample at rates anywhere
between 1-1,000Hz. Now consider the write time of a single byte in flash memory is
approximately 75s.
In comparison, FRAM technology can be written to at a rate of about one byte every 125
nanoseconds. This is close to 1000 times faster than flash! Now consider the application reaches
the end of a flash segment and needs to move to the next one, suddenly there is a 20 millisecond
latency while waiting for a segment erase to complete.
The erase latency does not apply to FRAM as it is not required to pre-erase FRAM bytes
between writes. A 20 millisecond latency every segment does not seem prohibitive until we
calculate how significantly it impacts the maximum write speed. For the purpose of this
discussion, consider that the block of memory being written to is 512 bytes in length. A flash
memory block can be written 26 times per second including the time taken to complete an erase
cycle every time 512 bytes are written. This brings us to a total speed of 13kBps [1].
In comparison, a 512 byte FRAM block can be written to at speeds greater than 8MBps [2]. Not
every application requires such high write speeds, but consider if your target application was
required to write only 1kB every second, the MCU with flash technology would spend 7% of the
time staying active to perform the write. However an FRAM MCU would complete that task in
0.01% of the time allowing the MCU to remain in standby 99.9% of the time, providing
significant power savings.
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