| 摘要 |
PROBLEM TO BE SOLVED: To provide an input device which prevents propagation of a high (H) level of input signal or power voltage into the interior of a chip when an n-channel transistor is provided between an input pad and an input buffer for making the input device have a breakdown voltage exceeding the power voltage to the input signal, and when the level of the input signal or power voltage drops. SOLUTION: A p-channel transistor P103 is connected in parallel to the n-channel transistor N103 for power protection to be turned on and off by a control signal c. Thus, when the level of the power voltage or input signal drops to its H level, the p-channel transistor P103 is turned on so that a potential applied to the input pad is propagated to the interior of the chip. When a signal not smaller than the power voltage is applied to the input pad IN, the p-channel transistor P103 is turned off. Simultanesouly, a substrate bias changeover circuit 104 changes a substrate bias for the p-channel transistor, thus preventing a leak voltage. COPYRIGHT: (C)2004,JPO
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