Bi-directional NFC interface chip harvests energy from RF emissions

November 05, 2012 // By Julien Happich
Operating on energy harvested from an NFC reader's RF emissions, the AS3953 NFiC (Near Field Communications interface Chip) requires no external power source and at most one external component (a capacitor).

The device enables system designers to add full bi-directional NFC capability at a total cost less than half that of a typical NFC reader implementation, which can require as many as 20 external components.

The AS3953 is fully compliant with NFC Forum specifications (NFCIP-1 target at 106kbps) and the ISO14443A industry standard (up to 848kbps, to Level 4). This means that it can be used in contactless smart cards and as an NFC Forum-compatible interface tag, and can establish instant communication with any NFC-enabled phone in close proximity (<10cm).

The AS3953 is expected to find uses in a wide variety of applications, including contactless passive programming of MCU-based systems, smart cards with displays, smart retail shelf labels, sensors and ultra low-power data loggers, medical devices, and secured NFC Bluetooth pairing.

It can also enable innovative new approaches to system designs by using an NFC-enabled smartphone as a display host and system controller for normally stand-alone devices, eliminating the requirement for the slave device to have its own display and processor. The AS3953 features a configurable wake-up interrupt, enabling a zero-power system design while in shut down. It also contains a complete analog front end, 1kB of internal EEPROM, and a 4-wire SPI with a 32-byte FIFO. The device can draw up to 5mA of harvested energy from the external magnetic field, and includes an internal power management circuit that can supply harvested energy to the application. This makes the AS3953 suitable for use with battery-powered and portable microcontroller-based devices. The AS3953 NFiC comes as a bare die or in a 10-pin, 3x3mm MLPD package.

Visit ams at www.ams.com/RFID/AS3953