Dual-interface memory applies energy harvesting to enable true battery-free system design
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 output pin. The nominal output voltage is between 1.7 to 2.3 V, allowing the memory to supply many types of devices including low-voltage CMOS ICs.
The electrical power available to drive external devices depends on various factors, such as the RF power of the reader, the distance between the reader and the memory’s connected antenna, and the relative sizes of the reader and memory antennas. Assuming adequate RF strength, an RFID device can even be used to power multiple items of equipment placed within range. The EEPROM’s energy harvesting mode can be turned on or off, and the maximum output current set from 300 µA to 6 mA, by adjusting settings in an internal register.
The M24LR16E is in volume production now and available in SO8, TSSOP8 or MLP8 surface-mount packages. Prices are $0.6 in SO8 and TSSOP8 and $0.66 in MLP8, for orders over 1000 pieces. Alternative pricing options may be available for higher quantities. The device may also be supplied in wafer form on request.
The evaluation board ROBOT-M24LR16E-A, demonstrating energy-harvesting capabilities of the M24LR16E dual-interface EEPROM, is available from ST.
Visit STMicroelectronics at www.st.com
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