Dual-interface memory applies energy harvesting to enable true battery-free system design

November 07, 2011 // By Paul Buckley
STMicroelectronics is extending the company’s family of RFID/NFC wireless memory ICs with a new 16-Kbit device that can also harvest enough energy to enable small electronic items using it to become completely battery-free electronic applications.

ST’s dual-interface memories, including the new 16-Kbit device, feature a low power I2C interface, as well as a 13.56-MHz ISO15693 contactless RF interface. The RF interface can harvest ambient radio waves emitted by RFID reader-writers and convert those waves into a voltage output that may be used to power other electronic components.

The energy harvesting capability of the EEPROM will enable new types of miniaturized electronics. ST has demonstrated the M24LR16E energy-harvesting wireless memory by illuminating indicator LEDs as well as by powering its battery-less STM8L-based Discovery kit. Other potential applications include e-paper devices such as electronic shelf labels, as well as industrial automation, sensing and monitoring systems, and personal healthcare products.

The M24LR16E features 16 Kbits of non-volatile EEPROM storage, introducing a new lower-density option alongside ST’s established 64Kbit dual-interface wireless memory, the M24LR64. ST anticipates a broad user base for these RFID/NFC-compatible devices as RFID is now widely used in supply-chain and retail businesses, and NFC technology will be included in more than 500 million mobile phones sold annually by 2015, according to figures from ABI Research.

ST’s dual-interface memories are EEPROMs that provide non-volatile storage for system parameters, data logged from external sources or program code. Each device provides an I2C serial interface as well as a wireless interface compatible with the ISO-IEC 15693 13.56MHz radio standard for RFID and ISO15693-capable NFC systems. The memory can communicate with the host system in the same way as a standard serial EEPROM, or it can be read/written directly using equipment such as an RFID reader or mobile phone. Wireless operation requires an antenna that can simply be etched on the printed circuit board.

A data protection scheme is built in, including 32-bit password protection to safeguard stored data against threats such as accidental over-writing and unauthorized access or tampering.

The new M24LR16E integrates additional power-management circuitry to make harvested energy available to other devices on the pc-board via an