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| A primer on semiconductor 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. |
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| 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. |
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| 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. |
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| 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). |
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| 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. |
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Figure 1: PZT crystal structure |
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Figure 2: Write speed comparison |
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*At 25 MHz, F-RAM writes 488 times faster than comparable EEPROM device. |
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