About F-RAM Memory

F-RAM (ferroelectric random access memory), pioneered by Ramtron International Corp., offers a unique set of features relative to other semiconductor technologies. Established semiconductor memories can be divided into two categories: volatile and nonvolatile. Volatile memory includes SRAM (static random access memory) and DRAM (dynamic random access memory), among others. RAM type devices are easy to use, offer high performance, but they share a common vulnerability: stored memory is lost when the power supply is removed.

The F-RAM chip contains a thin ferroelectric film of lead zirconate titanate [Pb(Zr,Ti)O3], commonly referred to as PZT (Figure 1). The Zr/Ti atoms in the PZT change polarity in an electric field, thereby producing a binary switch. Unlike RAM devices, F-RAM retains its data memory when power is shut off or interrupted, due to the PZT crystal maintaining polarity. This unique property makes F-RAM a low power, nonvolatile memory.

Like F-RAM, ROM (read only memory) is a nonvolatile memory that does not lose its data content when power is removed. Newer generation ROM, like EEPROM (electrically erasable programmable read only memory) and flash memory, can be erased and re-programmed multiple times, but they require high voltage and write very slowly. ROM-based technologies eventually wear out (in as little as 1E5 cycles), making them unsuitable for high-endurance industrial applications.

F-RAM has 10,000 times greater endurance and 3,000 times less power consumption than a typical serial EEPROM device, and nearly 500 times the write speed (Figure 2).

F-RAM combines the best of RAM and ROM into a single package that outperforms other nonvolatile memories with remarkably fast writes, high endurance and ultra-low power consumption.

Benefits of F-RAM

F-RAM has three distinct properties that make it superior to floating gate devices:

1. Fast write speed
2. High endurance
3. Low power consumption

Here are just a few broad industry applications where F-RAM surpasses competing semiconductor memory:

Power failure-prone environments

Any nonvolatile memory can retain a configuration. However, if the configuration changes and power failure is a possibility, the higher write endurance of F-RAM allows changes to be recorded without restriction. Any time the system state changes, it writes the new state. This avoids writing to memory on power down when the available time is short and power loss is imminent.

High noise environments

Writing to EEPROM in a noisy environment can be challenging. When severe noise or power fluctuations are present, the long write time of EEPROM creates a window of vulnerability (measured in milliseconds) during which the write can be corrupted. The probability of errors is proportional to the size of the window. A write transaction window for F-RAM is less than 200ns.

RFID systems

In the area of contactless memory, F-RAM provides an ideal solution. Low energy access is critical in RFID systems because the energy emitted in the field declines exponentially with distance. The tag must be close enough to the field to induce the minimum amount of energy to write and it must extract the energy while in the field. Applications that require writes (i.e. debit cards, tags used in manufacturing processes) can benefit by improved write distance, lower sensitivity to motion (time in the field), and lower RF power required for the transmitter and receiver.

Diagnostic and maintenance systems

In a sophisticated system, the ability to record the operating history and system state during a failure is enormously valuable. Without this data, the ability to accurately troubleshoot or perform the required maintenance can be difficult. Due to its high write endurance, F-RAM makes an ideal system log. Diverse systems — from workstations to industrial process control — can benefit from F-RAM.