| 摘要 |
PURPOSE:To prevent wasteful refreshing operations so as to reduce the power consumption of a dynamic RAM, by comparing the output voltage of a dummy storage element with a reference voltage and, when it is detected that the output voltage of the dummy storage element is lower than the reference voltage, generating a refresh signal. CONSTITUTION:The capacitor C2 of a dummy cell 10 is charged when all of the memory cells of a dynamic RAM are refreshed and, thereafter, gradually discharges. Since the dummy cell 10 has the same constitution as that of the memory cells, the discharging characteristic of the dummy cell 10 is the same as that of the memory cells and, when it is detected by a sense amplifier 14 that the output voltage of the capacitor C2 drops lower than the minimum voltage necessary for making refresh, a signal is outputted to a refresh requesting signal generating circuit 15. A CPU discriminates whether or not the dynamic RAM is accessed and, after the accessing operation is completed, refreshes the entire RAM. |
