| 摘要 |
PROBLEM TO BE SOLVED: To prevent electrostatic breakdown of an output buffer caused by surge current. SOLUTION: A control circuit (6) is employed, which controls an output buffer (4) in a high output impedance state at least for a prescribed time corresponding to potential rise of a power terminal (VCC). When a high tension surge is applied to an external terminal (3) connected to an output terminal of an output buffer, a power supply line (12) is made into several volts instantaneously on flowing of the surge current from an electrostatic protecting element (5) to the power supply line (12) and an inner logic circuit (2), and a control circuit (6) or the like become the same state as powered just for a moment. Because of the unstable state, even if a signal node of an inner logic circuit is at a logically intermediate level, a control circuit controls an output buffer in a high output impedance state for a prescribed time. Consequently, it is prevented that an input node of an output buffer is at an intermediate level due to the unstable state and current easily flows to an output buffer from an external terminal. COPYRIGHT: (C)2004,JPO&NCIPI
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