Patent ID: 8908671

Claim:
A semiconductor device comprising: a reception circuit configured to receive an amplitude-modulated carrier wave from an antenna, to demodulate said carrier wave, to extract a clock signal from the carrier wave, and to cause the extracted clock signal to cease to be generated based on disappearance of the carrier wave; a transmission circuit configured to transmit a signal modulated on the basis of transmission data from the antenna; a logic circuit configured to perform a data process for transmission/reception by the transmission circuit and the reception circuit; and a Phase Locked Loop (PLL) circuit configured to receive the clock signal extracted by the reception circuit, to generate an internal clock signal of the logic circuit, and to control synchronization of the internal clock signal with the extracted clock signal, wherein the PLL circuit comprises a phase frequency difference detection circuit configured to generate a charge error signal and a discharge error signal in accordance with a phase difference between the extracted clock signal and a feedback signal synchronized with the internal clock signal; an error current generation circuit configured to charge an output node upon receiving the charge error signal and to discharge the output node upon receiving the discharge error signal, the output node being coupled to an input of a low pass filter; and a voltage controlled oscillator circuit coupled to an output of the low pass filter, wherein the PLL circuit is further configured to continue to generate the internal clock signal during a period of disappearance of the carrier wave, wherein the error current generation circuit outputs an error current signal to the low pass filter which is based on the charge error signal and the discharge error signal, and wherein the error current generation circuit is configured to output said error current signal to cause the low pass filter to stop charging/discharging during the period of disappearance of the carrier wave input from the antenna.