Patent ID: 7681060
Filing Date: 2010-03-16
Classification: G06K

Abstract:
1. A semiconductor integrated circuit device comprising: a pair of antenna terminals connected to an antenna; a power supply circuit for rectifying and smoothing an alternating current signal supplied to the antenna terminals from the antenna to obtain a direct current voltage; first and second power supply terminals supplied with electric power from an external apparatus; a power supply switch circuit connected between the first power supply terminal and an output terminal of the power supply circuit; and an internal circuit which operates using a voltage generated by the power supply circuit received by the output terminal of the power supply circuit, wherein the power supply switch circuit includes: wherein, when the alternating current signal is obtained from the antenna, the first pull-up circuit short-circuits the gate terminal of the first MOS transistor to the first power supply terminal and the second pull-up circuit short-circuits the gate terminal of the second MOS transistor to the output terminal of the power supply circuit; and wherein, when no alternating current signal is obtained from the antenna, the first and second pull-up circuits stop operating and potentials at the gate terminals of the first and second MOS transistors become one of a plurality of setup potentials that are set so as to track in a direction from a potential at the first power supply terminal to a potential at the second power supply terminal, and wherein, when no alternating current signal is obtained from the antenna, the pull-down circuit sets potentials at the gate terminals of the first and second MOS transistors to one of said setup potentials.