| 摘要 |
<p>PURPOSE:To control the instantaneous drop of the internal power voltage at the time of turning on/off of an external power supply by providing a 2nd voltage detecting circuit which actuates a 1st selection circuit and a 3rd voltage detecting circuit which actuates the 2nd and 3rd selection circuits, respectively. CONSTITUTION:A voltage detecting circuit 7 controls the ON/OFF of a power supply where the threshold voltage V1 is set. A voltage detecting circuit 21 actuates a selec tion circuit 23 which uses an enable signal to which the threshold voltage V2 is set (V1>V2) and a prescribed potential as inputs. The selection circuits 24 and 25 have the threshold voltage V3 higher than the V1 and use an input/output bus and a pre scribed potential as the input, respectively. Then a voltage detecting circuit 22 actuates the selection circuits using the input/output bus and the prescribed potential as inputs, respectively. Therefore the signal lines securing the connection between the circuits 23 - 25 and a semiconductor storage device 20 are kept at each prescribed potential. Thus, the transient voltage is turned into the instantaneous voltage. Then it is possible to surely prevent the instantaneous voltage drop of an internal power supply of the storage 20 in the transient periods at rise and fall of a power supply as well as a latch-up state. In such a constitution, the high safety and the high reliability are se cured for the device 20.</p> |
