FRAM FAQ

Frequently Asked Questions

What is FRAM?

FRAM, an acronym for ferroelectric random access memory, is a non-volatile memory that can hold data even after it is powered off. In spite of the name, FRAM is a ferroelectric memory and is not affected by magnetic fields as there is no ferrous material (iron) in the chip. Ferroelectric materials switch polarity in an electric field, but are not affected by magnetic fields.

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What are FRAM’s key advantages over Flash/EEPROM?

1) Speed. FRAM has fast write times. Beyond all the other operations, the actual write time to an FRAM memory cell is less than 50ns. That is approximately 1000x faster than EEPROM. Additionally, unlike EEPROM where you must have two steps to write data: a write command, followed by a read/verify command; FRAM’s write memory function happens in the same process as read memory. There is only one memory access command, one step for either reading or writing. So in effect, all the time associated with an EEPROM write transaction is effectively eliminated in an FRAM-based smart IC.

2) Low Power. Writes to the FRAM cell occur at low voltage and very little current is needed to change the data. With EEPROM high voltages are needed. FRAM uses very low power – 1.5v compared to 10-14v for EEPROM. FRAM’s low voltage translates into low power usage and enables more functionality at faster transactions speeds.

3) Data Reliability. Because only a small amount of energy is required, all the necessary power for FRAM is front-loaded at the beginning of data write. This avoids “data-tearing,” a partial write of the data which occurs when EEPROM based smart ICs are removed from the RF field power source during a write cycle. Further, FRAM experiences 100 Trillion read/write cycles or greater – far exceeding EEPROM write cycles.

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How does FRAM perform at high temperatures?

FRAM is a very robust and reliable memory technology, even at high temperatures. FRAM retains its data for more than 10 years at 85 degrees C. This far exceeds the requirements for credentials in the government ID market and represents the robust data retention of FRAM. FRAM is used in several automotive applications and has been qualified to withstand the extremely harsh conditions.

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Does FRAM have the same problem with scalability as Flash/EEPROM?

Unlike FRAM, Flash/EEPROM employs a floating gate charge storage design which necessitates high voltage and costly, power-hungry and space-hogging circuits, such as transistors and charge pumps. A restriction of all this high-voltage legacy circuitry is that it does not easily scale to smaller and smaller IC process node manufacturing. Also, TI's advanced 130 nanometer (nm) FRAM manufacturing process results in chips that are much smaller than the 180 – 220 nm node sizes used by in most Flash and EEPROM-based embedded microcontrollers, giving FRAM products a significant advantage in size, performance, and power efficiency. Further, the FRAM manufacturing process is fully compatible with digital CMOS processes making the technology easy to scale to smaller technology nodes in the future.

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Does FRAM lose data after a read?

No. FRAM is a nonvolatile storage memory that retains its data even after the power is turned off. Similar to commonly used DRAM (Dynamic Random Access Memory) found in large (main) memories in personal computers, workstations, and non-handheld game-consoles (such as PlayStation and Xbox), FRAM requires a memory restore after each read. A memory restore is done because like DRAM, FRAM memory cells require each bit accessed to be re-written in a refresh function. Because FRAM has an inexhaustible write endurance (100 trillion write/read cycles), this is not a practical concern.

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Does new embedded FRAM memory technology raise security concerns?

FRAM is already used in financial smartcard applications in transit and in set-top boxes.  Compared to existing EEPROM technologies, FRAM is more resistant to data corruption via electric fields, radiation, etc.  The extremely fast write times and the small 130 nanometer (nm) process node make it difficult for attackers. Furthermore, FRAM’s lower power consumption (and the fact that its read and write power consumption is identical) arguably make it a more difficult target to attack using differential power analysis techniques. 

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Are FRAM devices affected by magnetic fields?

A common misconception is that ferroelectric crystals contain iron or are ferromagnetic or have similar properties. The term “ferroelectric” refers to similarity of the graph of charge plotted as a function of voltage (Figure below) to the hysteresis loop (BH curve) of ferromagnetic materials. Ferroelectric materials are not affected by magnetic fields.

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How large of an electric field can a FRAM device withstand?

The FRAM memory cell operates by applying a switched voltage to sense and restore the data state. The ferroelectric film PZT is about 70nm thick. If the device is placed in a 50 kV field at 1 cm, it is not possible to produce more than 1V across the ferroelectric film. As a practical matter, FRAM devices are impervious to external electric fields.

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Is FRAM affected by radiation or soft errors?

Volatile memories, DRAM and SRAM, use a capacitor to store charge or a simple latch to store state. These cells can be easily upset by a alpha particles, cosmic rays, heavy ions, gamma, x-rays, etc. which cause bits to flip to an opposite state. This is called a soft error, since a subsequent write will be retained. The rate at which this occurs is called the Soft Error Rate (SER) of the device. Because the FRAM cell stores the state as a PZT film polarization, an alpha hit is very unlikely to cause the polarization to change a given cell’s state and the FRAM terrestrial SER is not even measurable.

This ‘radiation resistant’ characteristic of FRAM makes it attractive for use in several emerging medical applications

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What is TI’s focus in FRAM?

While TI is currently producing standalone FRAM memory devices for Ramtron, our internal focus is on

  • Embedded FRAM (as a 2 mask adder to digital process flow). We have successfully designed arrays up to 32Mb. <
  • FRAM as a true NVRAM technology to replace cache SRAM, DRAM, Flash / EEPROM
  • Supporting 1.5V operation for low power applications

While FRAM does provide unparalleled flexibility and benefits to customers, initial implementations and designs are optimized for targeted areas of operation. It is important to emphasize that FRAM technology can support both high performance and low power applications; however, our current FRAM array designs are optimized for low power operation. Some items to consider with our initial FRAM designs are:

  • They are best suited for devices operating below 25 MHz. However, as with all technology evolutions, we expect to design higher performance FRAM memory arrays in the future that support devices operating at much higher clock speeds.
  • As stated above, we expect that several of our initial FRAM memory devices will use 2T-2C configuration (2 cells are used for each bit of data). This ‘redundant’ methodology results in the crossover point where FRAM arrays are smaller than equivalent Flash memory in memories lower than 64KB – 128KB (depending on design requirements). Again we expect that this crossover point will increase in 1T-1C operation and in future process technology shrinks.
  • TI is also currently not targeting its embedded FRAM products for automotive applications.

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Is F-RAM and FeRAM the same as FRAM?

Yes. F-RAM, FeRAM and FRAM are synonymous. Texas Instruments has chosen to use the acronym “FRAM” while Ramtron has chosen “F-RAM”.

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Are there commercially available FRAM products in the market?

FRAM is commercially proven in the semiconductor market with more than 150 million units sold by Ramtron alone. Ramtron’s F-RAM memory products have become a very popular choice in high quality industries such as automotive. Manufacturers such as Mercedes, GM, BMW, Ford, Porsche, and others, are now using FRAM in their automobiles.

TI is currently producing Ramtron’s 4-Mb and 2-Mb FRAM memory on its advanced 130-nanometer (nm) FRAM manufacturing process (http://www.ramtron.com/products/nonvolatile-memory/parallel.aspx). Ramtron’s 4-Mb FRAM memory product was named 2008 Product of the Year by Electronic Products China (EPC) Magazine.

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