| 摘要 |
A portable computer and a key input device thereof are provided to offer a separate keypad, such as a numeric keypad, for a special purpose based on a switch using capacitance change. A capacitance unit(120) changes capacitance by an external touch at a lower part of a mainframe. A signal detector(130) detects a difference of the capacitance change as a key signal. The capacitance unit comprises a plurality of charge sensor capacitors formed in a matrix shape. The capacitance unit changes a capacitance value in proportion to a distance from a finger. The signal detector is a PSoC(Programmable System on Chip) and includes a unit, such as a serial bus(131), transferring a detected signal to a host(140).
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