An FeRAM cell configuration

Getting the right memory for energy harvesting

TI promotes cinderella FeRAM technology for next generation sensors.

Ferroelectric RAM (FeRAM) could help overcome a major challenge facing energy-harvesting devices for highly sensitive applications, according to research Texas Instruments (TI) presented at the International Solid State Circuits Conference.

Energy harvesting has been proposed as a way of powering tiny sensors for applications in healthcare, building maintenance and the monitoring of safety critical systems. But it faces the problem that the technique is highly susceptible to the environment – for example, solar-powered devices depend on the presence of sunlight.

In many cases, the problem is not simply making sure that a device can power up if necessary but also that it retains some memory of its state should power run out. A further complication is the energy demanded by the better-established memory technologies and their potential impact on the size of sensors that need to be as small as possible.

“Flash or EEPROM as today’s standard non-volatile memory is slow in write access and has high peak current demands due to the required charge pump for erase and write cycles,” TI’s paper says. “SRAM could be used for fast low-power read/write, but it requires a separate battery for state retention.”

In response, TI has developed a 24MHz, 16b microcontroller with embedded FeRAM operating at 82uA/MHz. The addition of the FeRAM requires two additional mask layers for the full system-on-chip. In trials, TI says that it provided 1,000X faster write at 100X lower power consumption than a typical flash-based MCU.

TI has been one of FeRAM’s main promoters for almost a decade, along with Ramtron and Fujitsu Semiconductor. Many other chipmakers have also researched and made several product releases using the technology.

FeRAM is structurally similar to DRAM but uses a ferroelectric rather dielectric layer to give it non-volatile attributes.

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