| 摘要 |
PURPOSE:To set the test mode without providing a private test terminal by providing a low voltage detecting circuit in a single semiconductor substrate and setting the test mode when a supply voltage is lower than a certain reference voltage. CONSTITUTION:Depletion transistors (TR) 3 and 4 and an inverter 5 constitutes the low voltage detector. Since TRs 3 and 4 are regarded as resistances equivalently, the input line to the inverter 5 is fixed to a potential, which is obtained by dividing a supply voltage VDD by resistances, and is set to a value between the voltage VDD and the ground voltage. The test mode is set when a test mode signal line 6 is in the high level, and the normal mode is set when the line 6 is in the low level, and the switching voltage of the inverter 5 is set between the lower limit of the operating supply voltage and the operation securing voltage. Thus, the test mode is set without providing the private test terminal.
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