Zurich University reveals FRAM tech for green wireless apps

Ramtron International Corp. has announced that the Zurich University of Applied Sciences Institute of Embedded Systems (ZHAW InES) released the details of the research conducted with Ramtron FRAM designed into a battery-free wireless sensor node. The research showed that the use of FRAM nonvolatile memory in energy harvesting applications can reduce energy consumption of the wireless sensor node by more than 40 per cent while reducing the total wireless sensor system cost, as compared to systems built with standard nonvolatile memory components.

Wireless sensor networks are designed into modern building automation systems. A wireless switch, for example, can operate without batteries or hardwired electrical infrastructure. The switch uses energy harvested from solar, mechanical or piezoelectric input (energy formed by compressing or deforming a material). The minute amount of energy given off from the switch is sufficient to power up a transmitter that sends a radio signal to a receiver that powers up lighting or other systems in a home or office. The wireless switch is economical and eliminates wiring, battery replacement and labour costs. A wireless switch can also provide creative design flexibility for architects, as the wireless switch can be positioned virtually anywhere, uninhibited by wires and conduit.

The research led by Marcel Meli, ZHAW, concluded that the use of FRAM nonvolatile memory in a wireless switch can improve the performance of energy harvesting powered ZigBee wireless nodes (low-power digital radio). "The justification for using a wireless switch comes from lower installation and maintenance costs, but a ZigBee-sensor requires a lot of overhead. The more energy is required, the more expensive the system," said Meli. "We have discovered that by using the inherently low-power FRAM from Ramtron in our experimental board designs, more energy is available for the transmitter and other functions, like saving the processor status. We also recognise the longevity of the FRAM cell. Compared to traditional nonvolatile memories like EEPROM or flash, FRAM can be rewritten virtually forever—well in excess of a typical wireless product's lifetime."

Meli's research also suggests that FRAM can reduce the total BOM associated with wireless sensor nodes powered by harvested energy. By using FRAM to restore the state of the processor only when enough energy is available, less power management is required and there are fewer constraints on the storage system, thereby reducing system complexity and component costs.