A Highly Stable and Reliable 13.56-MHz RFID Tag IC for Contactless Payment

Radio frequency identification (RFID) has been widely used for contactless payment. However, modifying sensitive data such as balance stored in an RFID tag over an air interface requires high stability and reliability, particularly when the tag is being moved away from the RFID reader (such phenomenon is called card tear). Previous countermeasures of card tear operation are mainly based on contact smart card; however, when the tag is contactless, the variation of magnetic field should be also taken into account. To solve card tear problem, this paper presents a fully integrated 13.56-MHz RFID tag IC with reliable power supply and antitearing mechanism. Proposed are the following solutions: 1) to provide a 4-kV multifunction electrostatic discharge protection circuit with rectifier and limiter; 2) to develop a low dropout circuit and a low voltage detection circuit; 3) to design a well-run antitearing mechanism, which can protect the tag from being incorrectly written; and 4) to design a digital circuit with several functions, including 3DES, micro control unit, and electrically erasable programmable read-only memory. The proposed RFID tag IC was fabricated using a 0.18- $\mu\hbox{m}$ process with an area of 3 $\hbox{mm}^{2}$. The measured results indicate that the tag operates in a stable and reliable mode without any problem caused by card tear.