| 摘要 |
PURPOSE:To further reduce power consumption at the time of autorefresh (ATRF) mode in an artificial static memory having a built-in ATRF circuit by making oscillating frequency of an oscillator for substrate voltage generating circuit different between active time and ATRF time. CONSTITUTION:Minimum operating period of DRAM is, for instance, 270nsec, and substrate current at this time is as large as several tens of muA. Accordingly, a substrate voltage generating circuit must have capacity to absorb this substrate current. However, in ATRF mode, refresh period is 15.625musec or more and substrate current becomes less than 1muA. Accordingly, it becomes possible to lower the capacity of the substrate voltage generating circuit and reduce power consumption remarkably. Executed example shows an oscillator for substrate voltage generating circuit constituted of three steps of inverter, a substrate voltage generating circuit and a timer. At the time of ATRF mode, load of the inverter is made larger through a switching device, and oscillating period of the oscillator is made longer. Thus, power consumed in the substrate voltage generating circuit is made smaller.
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