Communication circuit

摘要

In a communication circuit, an RFIC includes an IO terminal and a control IC includes an IO terminal. A variable capacitance element includes control terminals, a capacitance element with a capacitance value that is determined according to a control voltage, and a resistance voltage divider circuit configured to generate the control voltage by dividing a voltage inputted to the control terminals. One of the RFIC and the control IC supplies control data to the variable capacitance element via a signal line. The variable capacitance element, along with an antenna coil, constitutes an antenna circuit of an LC parallel resonance circuit, and sets a resonant frequency of the antenna circuit to be a predetermined frequency.

主权项

1. A communication circuit comprising:
an RFIC configured to perform modulation and demodulation between a baseband signal and a high-frequency signal, and including a signal terminal and a plurality of IO terminals; an antenna coil; and a variable capacitance unit configured to change a resonant frequency of an antenna circuit including the antenna coil; wherein the antenna coil is connected to the signal terminal of the RFIC; the variable capacitance unit includes a capacitance element having a capacitance value that is determined according to a control voltage, and is connected to a resistance voltage divider circuit; the resistance voltage divider circuit includes:
a plurality of resistances each including a first terminal connected to each of the plurality of IO terminals of the RFIC, and a second terminal; anda common line to which the second terminals of the plurality of resistances are connected in common and through which the control voltage is outputted; the resistance voltage divider circuit is configured to generate the control voltage by dividing an input voltage; and resistance values of the plurality of resistances are determined to be in a ratio based on powers of 2 based on a lowest value among the resistance values.