FRAM Ferroelectric Random Access Memory Tutorial

- essentials of FRAM, ferroelectric random access memory, or FeRAM, detailing what it is, how it works and its advantages and disadvantages..

Ferroelectric RAM, FRAM, also referred to as FeRAM is one of a variety of forms of memory that is now available to developers.

F-RAM is a form of non-volatile memory and this means that it is a direct competitor with Flash memory, although there are several advantages and disadvantages to using it.

While the name FRAM or ferroelectric RAM seems to indicate that an iron element exists within the memory this is not actually the case.

Ferroelectric RAM history

The development of FRAM dates back to the early days of semiconductor technology. The idea was first proposed in 1952, but it took many years before the idea started to be developed properly as the technologies required to implement it did not exist.

Some work on the technology was started in the 1980s, and then in the early 1990s a part of NASA undertook work into the technology for detecting UV radiation pulses.

However around 1999 the first devices were produced and since then companies including Ramtron, Fujitsu, Texas Instruments, Samsung, Matsushita, Infineon and other have been using the technology.

FRAM usage

Currently ferroelectric RAM is not as widely used as many of the more established technologies including DRAM and Flash. These technologies have become well entrenched and their use is widespread. As developers often tend to rely on trusted technologies that are guaranteed to deliver the performance they require, they are often reluctant to use technologies like FRAM that are not guaranteed to deliver. Also issues like memory density that limit the size of memory available have caused them not to be so widely used.

However FRAM technology is now being embedded into chips using CMOS technology to enable MCUs to have their own FRAM memories. This requires fewer stages than the number required for incorporating Flash memory onto MCU chips, thereby providing some significant cost reductions.

The basic cell of the ferroelectric memory showing the connections to the capacitor and FET.
Basic Ferroelectric memory cell

A further advantage, apart from the non-volatile nature of the memory is its very low power consumption which lends itself admirably to use within MCUs where power consumption is often a key issue.

Comparison of FRAM and other technologies

In order to decide whether to use FRAM memory technology, it is often necessary to compare its operation and capabilities with other contender memory technologies.

Comparison of Memory technologies with FRAM
Non-volatile Yes No Yes Yes
Write endurance 1 million billion (i.e. 10^15) Unlimited ~500 000 10 000
Write speed (for 13 kB) 10ms <10ms 2s 1s
Average active power (µA/MHz) 80 <60 Up to 10 mA 260
Dynamics bit addressable programmability Yes Yes No No

FRAM advantages and disadvantages

FRAM has a number of distinct advantages when compared to Flash memory which is its nearest competitor. However it also has a number of disadvantages. These need to be balanced against the requirements for the overall system when choosing whether to use Flash or FRAM memory for an electronic system.

  • Lower power usage
  • Faster write performance
  • Much larger number of write-erase cycles
  • Lower storage density
  • Overall capacity limitation
  • Higher cost

As a result of the various advantages, FRAM memory is being used in a variety of instances and it provides developers with an additional option for a choice of memory. Aspects including its almost unlimited life and speed make it an attractive option in a number of instances.

By Ian Poole

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