Patent ID: 7248526

Claim:
A refresh period generating circuit which generates a refresh period in refreshing a DRAM cell, comprising: an oscillation circuit which oscillates at an oscillating frequency with temperature dependence on ambient temperature; a dividing circuit which divides an oscillation output of said oscillation circuit and outputs signals having a plurality of different frequencies; a temperature detector which detects said ambient temperature; and a selector which switches and selects among the signals of said dividing circuit based on an output of said temperature detector, and outputs a signal as a reference of said refresh period, wherein said oscillating frequency of said oscillation circuit has substantially said temperature dependence at least within a range from a first temperature point to a second temperature point lower than said first temperature point, and wherein said selector selects and outputs a signal of said dividing circuit having a frequency depending on said temperature dependence of analog form when said temperature detector detects a temperature within a range from said first temperature point to said second temperature point, selects and outputs one or more signals of said dividing circuit each having a frequency higher than said frequency depending on said temperature dependence of analog form when said temperature detector detects a temperature higher than said first temperature point, and selects and outputs one or more signals of said dividing circuit, each having a frequency lower than said frequency depending on said temperature dependence of analog form when said temperature detector detects a temperature lower than said second temperature point.