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1Mb FRAM replacement for SRAM

Posted: 04 Apr 2005 ?? ?Print Version ?Bookmark and Share

Keywords:ramtron international? ramtron? ferroelectric random access memory? fram? sram?

Ramtron International Corp. has finally offered a non-volatile ferroelectric random access memory (FRAM) that is designed to be a drop-in replacement for standard asynchronous SRAMs. The company's latest 3V, 1Mb FRAM, which comes in a 32-pin thin small outline plastic (TSOP) package, offers virtually unlimited read/write cycles.

While FRAM is known for high write-endurance, some applications needed more cycles than FRAM could offer. Not anymore. The FM20L08 allows users to access each address a million times per second for hundreds of years with no wear out, according to the company.

Density drive
Ramtron jumped from a 256Kb FRAM offering to its latest 1Mb device in less than a year. The company's latest device, its highest-density FRAM memory, provides fully compatible SRAM timing with address transition detection (ATD). The FM20L08 is tailored to drop directly into an SRAM design with a JEDEC 128Kx8 SRAM pinout and 60ns access time. The high-speed page mode operation runs up to a 33MHz bus speed for a 4-byte burst.

Ramtron offers the device in both an industrial temperature range of -40C to 85C and a commercial temperature range of 0 to 70C. Cycle times are 150ns and 350ns, respectively.

With a standard SRAM pinout, the RM20L08 operates like an SRAM. It provides nonvolatile storage; therefore, battery backup is not required, which lowers the cost of using an FRAM versus SRAM. Operating at 3.3V, the FM20L08 uses less operating current than standard SRAMs. Fujitsu Microelectronics America Inc. introduced its 1Mb FRAM late last year, but Ramtron has made key improvements by reducing both read and write cycle times. Fujitsu's device was introduced in a larger 48-pin TSOP package.

More features

If you're a designer in the set-top box, automotive telematics or industrial applications space, you might want to consider FM20L08 over a standard SRAM product. This latest version is equipped with a voltage monitor that oversees the power supply voltage and will issue an active-low signal indicating that the memory is write-protected when VDD drops below a critical threshold. By locking out access to the memory when VDD is low, data corruption is easily avoided.

The device is also equipped with software-controlled write protection. The memory array is divided into eight uniform blocks, each of which can be individually write protected; the settings are nonvolatile. An address and command sequence drives the write-protection mode. To change write protection, the system host issues six read commands and two write commands. The specific sequence of read addresses must be provided to access the write-protect mode.

More information on read- and write-cycle AC parameters, power cycle timing, data retention, and capacitance is available for industrial and commercial temperatures.

The company plans to be in volume production by the second half of this year. FM20L08 samples are available in a 32-pin TSOP. In 10,000-piece quantities, pricing starts at $13.65 each. The part will also be available in a Pb-free package.

- Ismini Scouras

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