The Interface Circuit Design Of Contactless IC Cards

In this paper, the RFID interface circuit is designed by comparing the characteristics of the existing products, which meet the high-speed signal described in the latest ISO/IEC14443-2. This circuit including rectifier, regulator, clock generator, Power-on-Reset, demodulator and modulatorThe rectifier circuit can convert AC to DC by NMOS gate cross-connected bridge rectifier structure. The regulator is constituted by a limiter part and a regulator part that provides power to the circuit. The clock signal generator is extracted the 13.56MHz square wave from the antenna signal by low-power comparator and provide the clock signal to the circuit. The chip also generates two different Power-on-Reset signal for digital circuits. Demodulator separately extracted falling and rising edge in input signal, and then synthesized digital signal to a digital circuit, achieve high-speed demodulation circuit.This interface circuit can be working the magnetic field intensity 1A/m-8A/m, while The demodulation circuit can demodulate the data from the interrogator by"type A"or"type B"ASK modulation, and communication from interrogator to transponder can use the bit rate of 848kbit/s, 424kbit/s, 212kbit/s, 106kbit/s. Power management circuitry produces 1.8V-2.2V power supply voltage to the circuit, A Power-ON Reset allows to generate a power-up signal after a power supply level up to 1.7V. and generate a power-down signal after a power supply level down to 1.4V. According to ISO/IEC10373, the card reader model simulation is build up. The designed circuits are simulated with this model, and the analog front-end circuit works normally.As the chip, taking into account low-power design, the entire interface circuits control the maximum current of about 40.0μA.