| 摘要 |
PURPOSE:To detect the voltage drop of the data bus terminal of an IC memory, by connecting the joint between a resistor connected between both input terminals and a Zener diode to the base of a transistor via a resistance and providing an output point to the collector of the transistor. CONSTITUTION:A resistor 8 having the sufficiently large resistance value compared with the emitter-collector resistance value is provided when a transistor TR7 is turned on. Thus the power supply voltage Vcc of an IC memory emerges substantially to an output terminal. When the voltage Vcc lowers, the currents flowing to a resistor 4 and a Zener diode 6 reduce. Thus the voltage at a joint between the resistor 4 and the diode 6 is constantly set at Vz. When the voltage Vcc lowers less down to a level equal to the voltage Vz, no base current flows to turn off the TR7. Therefore, the fluctuation of the voltage Vcc is detected and delivered to a terminal 3 after setting the Zener voltage at a proper level and before the voltage Vcc lowers so less that the data bus terminal of the IC memory becomes uncirtain. |
