time: 2015-05-25 17:28

Ams AG has launched the AS3955, a Near Field Communication (NFC) interface chip that features energy harvesting and data-transfer capabilities. According to ams, the AS3955 is designed to provide a contactless bridge between an NFC reader (for instance, a smartphone or tablet) and a microcontroller residing on the host device. The AS3955 can also act as a power supply for the host device, the company reports, harvesting as much as 5mA at 4.5 volts—enough to charge a lithium-ion cell battery—from the RF energy radiated by an NFC reader.

AS3955 block diagram

The AS3955 is available with two bi-directional data-transfer modes: The extended mode allows the use of standard NFC tag commands to transfer data with minimum processing overhead on the host microcontroller, while the tunneling mode provides a flexible channel between the reader and the host microcontroller. Together, the two modes let a user implement any standard or proprietary communication protocol. Neither mode requires data buffering in the AS3955's EEPROM memory (2 kilobits or 4 kilobits), resulting in faster data transfers, according to ams.

The AS3955 features an RF front end that connects to a simple external NFC antenna without additional external components required. The chip also includes an SPI or I2C interface for communication with a microcontroller on the host device. The chip is fully compliant with the ISO1 4443A standard up to Level 4, as well as with NFC Forumspecifications, supporting both Type 2 Tag standalone functionality, and Type 4 Tag emulation in combination with an external MCU.

The energy that the AS3955 harvests from an NFC reader enables it to operate without an external power supply. This harvested energy can also be used to power external circuitry on the host device, enabling the implementation of standalone, eco-friendly, battery-less product designs, such as wireless sensor interfaces, interactive games and toys, smart price tags in shops and smart payment cards. The AS3955 can operate in stealth mode, which enables the host MCU to deactivate the AS3955's RF channel via the I2C or SPI interface after an operation, such as Bluetooth pairing, has been completed successfully. According to ams, this feature provides for guaranteed user control of NFC operation. The AS3955 also offers 32-bit password protection of its EEPROM memory.

The AS3955 also has a silent mode for fail-safe Bluetooth pairing—if the host's battery has an insufficient remaining charge to power its Bluetooth module, the chip automatically disables its RF circuitry to prevent the device from initiating a pairing procedure.

The energy- and data-management features are suitable for a range of uses in industrial, consumer and gaming equipment, ams reports. Products can be configured or personalized, for instance, at the end of a factory's production line, without the need to be powered. The high transfer speed and energy-harvesting capability reduce the amount of time required to download configuration data, according to ams, thereby helping to increase throughput in high-volume manufacturing lines.

The AS3955 is available now in production volumes in a 10-pin MLPD package measuring 3 millimeters (0.1 inch) by 3 millimeters (0.1 inch). Wafer-level chip scale package (WL-CSP) and sawn wafer are available on request. In the WL-CSP version, unit pricing is $0.98 each in an order quantity of 1,000 pieces. A demonstration kit for the AS3955 is available online from the ams' ICdirect web store.

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