Semiconductor device having individual power supply lines shared between function blocks for discharging surge without propagation of noise

摘要

Digital circuits (32c) undesirably producing noise and an analog circuit (32e) sensitive to the noise are fabricated on a single semiconductor chip (31), and are powered through a first set of positive power supply line and ground line (VDD10/GND10) and a second set of positive power supply line and ground line (VDD11/GND11), respectively; normally-off type field effect transistors (Qn1/Qn2/Qn3) are selectively connected between the positive power supply lines and the ground lines, and are responsive to electro-static surge voltage so as to turn on for discharging from one to another; however, the normally-off type field effect transistors do not turn on in the presence of the noise, thereby preventing the digital circuits and the analog circuit from the electro-static surge voltage and the noise. <IMAGE>