| 摘要 |
PURPOSE:To simplify the circuit by constituting at least a kind of diode among plural diodes having different reverse dielectric strength so as to reduce kinds of the titled static electricity protection circuit in the static electricity protection circuit having diodes connected between terminals and a positive or negative power supply and parasitic diodes between the positive and negative power supplies. CONSTITUTION:Diodes 1, 2 having a low dielectric strength are used for input/output terminals of a conventional power supply system VSS and high dielectric strength diodes 3, 4 are used for input/output terminals of a high dielectric strength power supply system VH in an IC having multi-power supply system. Since low dielectric strength diodes 1, 7 cannot be used in using the diodes for terminals of the VH system if switches 6, 7 are closed, the switches 6, 7 are opened and the diodes are used by closing switches 8, 9. Thus, the static electricity protection for all the input/output terminals is realized by using one kind of circuit and slight modification of metallic wire regardless of the 2-power supply system. The circuit is arranged definitely near the pad of each terminal in the layout of an IC and only the metallic wire has only to be switched depending whether each terminal belongs to which power supply system and the circuit is much simplified. |
