Oki Semiconductor Co., Ltd.

Lapis Semiconductor Co., Ltd.

Nobumasa Higemoto

Takashi Taya

Shinji Tanabe

A wireless key system and location detection method determine whether a wireless key is located inside or outside a main body. A communication device in the main body transmits a wireless signal using an inner antenna and an outer antenna outside the main body having a different directivity. A wireless key measures direction of movement of the wireless key when the wireless signal is received by one of antennas having different directivities, detects one of the antennas receiving the highest signal level of the wireless signal as a first antenna, selects one of the antennas having the same directivity as the inner antenna as a second antenna according to the measured direction of movement and detected directivity of the antenna, and decides that the wireless key is inside the main body based on the signal levels of the wireless signals received by the first and second antennas.

Wireless key system and key location determination method

An analog semiconductor integrated circuit has an analog circuit, a PMOS and a bias adjustment circuit. The gate of the PMOS is the output section of an open drain system, and is connected to an internal node on the output side of the analog circuit. The bias adjustment circuit is connected to the internal node, and allows adjustment of the bias current in accordance with the fuse disconnection number. The relationship between the voltage when a fixed current flows to an input terminal and the fuse disconnection number that allows the optimum bias current to flow to the output section of the analog LSI is checked by using a plurality of sample analog LSIs having different threshold voltages. The voltage is measured by causing a fixed current to flow to the input terminal of a non-sample analog LSI, and the fuse disconnection number corresponding with this voltage is obtained. Thus, the fuses in the bias adjustment circuit are disconnected.

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Kanagawa, Japan

Nobumasa Higemoto