Ferroelectric RAM
Ferroelectric RAM (FRAM) is a type of non-volatile memory similar to EEPROM but based on electric field orientation and with near-unlimited number (exceeding 1010 for 5V devices and even more for 3.3V ones) of write-erase cycles.
Constructionally, FRAM is a DRAM with the dielectric layer in the memory capacitors replaced with a thin ferroelectric film, typically made of lead zirconate titanate (PZT). The main vendor of FRAM chips is Ramtron International.
The bit is read by applying an electric field on the memory capacitor. The amount of charge needed to flip the memory cell to the opposite state is measured and the previous state of the cell is revealed. This means that the read operation destroys the memory cell state, and has to be followed by a corresponding write operation, in order to write the bit back. This makes it similar to the ferrite core memory. The requirement for a write cycle for each read cycle, together with the high but not infinite write cycle limit, poses a potential problem for some special applications.
It is possible to make FRAM cells as an additional step during normal semiconductor manufacture, leading to the possibility of full integration of FRAM into microcontrollers and other chips.
FRAM does not yet offer the bit density of DRAM and SRAM, but is non-volatile, is faster than flash memory (write times under 100 nanoseconds, roughly as fast as reading), and has very low power requirements, as unlike the EEPROMs they do not require a charge pump. It is expected to replace EEPROM chips in applications where very many write cycles are required. The very low current consumption makes them suitable for contactless chip cards.