The AS3921 is an NFC analogue front end (AFE) and comes with the company’s boostedNFC technology, which is capable of increasing the useable operating volume of an NFC reader significantly. This technology helps to improve the reliability and perceived speed of NFC transactions, particularly in devices that only have room for an extremely small antenna. It also ensures reliable NFC transmission in other device types which have a smaller antenna than a contactless card’s, or which present difficult operating conditions for NFC transmissions.
The AS3921 has been designed to enable OEMs to implement a simpler design than conventional NFC controller-based architecture allows, resulting in a simpler and cheaper solution, occupying a board footprint around one third smaller, using fewer components and consuming less power.
The chip draws 12µA in normal operation, and providing a power-saving Secure Element wake-up function, the AS3921 drains far less power from the battery than NFC controller circuits, which typically draw 60µA or more. Packaged in an ultra-compact wafer-level chip-scale package (WL-CSP) measuring just 2.115mm x 1.735mm, and connecting directly to the Secure Element with few external components required, the AS3921 with boostedNFC technology implements active load modulation: it generates an RFID card response which is synchronous to the reader’s field. This allows for card-to-reader communication at coupling factors as much as one order of magnitude lower than is possible with the passive load modulation (PLM) used by contactless cards.
The AS3921 complies with the ISO/IEC 14443 (types A and B) and FeliCa RFID protocols.
For easy integration into existing products, the NFC analogue front end AS3921 can connect directly to the contactless interface of the Secure Element through an ACLB or NFC-WI interface. An on-chip EEPROM allows the operating settings to be selected and programmed by the customer. The AS3921 can also be connected to an NFC tag or NFC interface chip.
The chip provides Q factor adjustment and implements automatic power control in order to avoid saturation of the reader and to provide reliable operation even in environments which hamper NFC transmissions. This makes it easier for equipment manufacturers to achieve interoperability with all kinds of standard-compliant and non-compliant readers.
