Semiconductor integrated circuit

摘要

A semiconductor integrated circuit is provided to allow a stable operation even in a short distance where an IC card is in contact with a reader/writer. In a semiconductor integrated circuit for a noncontact IC card that obtains driving power supply by carrying superimposed data, obtained voltage does not become overvoltage and data can be demodulated with stability regardless of a change in communication distance. Inputs of a system (including a rectifier circuit (80) and a power supply circuit (81)) producing power supply from an antenna coil (62) of the IC card which receives radio waves (66) transmitted from a reader/writer (64), and of a demodulator circuit (83) are connected via a path separated from the output of the rectifier circuit (80). Thus, a power supply voltage range can be set within a permissible value and a rate of change in input of the demodulator circuit can be obtained regardless whether the communication distance is short or long. <IMAGE>