| 摘要 |
PROBLEM TO BE SOLVED: To reduce the variation of a time required for programming by a method wherein a charge pump which supplies a current to a memory cell corresponding to a selected bit line is provided and the driving capability of the charge pump is controlled in accordance with the output of a counting means. SOLUTION: The number of selection signals which are included in a selection signal string inputted from a terminal Din and whose values are is counted by a counting means 15. In accordance with the counting result of the counting means 15, a switching means are is and closed so as to connect a corresponding oscillator 17, 18, 19 or 20 to a charge pump 13. As the frequency of a clock signal inputted to the charge pump 13 is changed by the output of the counting means 15, a current value supplied from the charge pump 13 is changed accordingly. As the driving capability of the charge pump 13, i.e., the number of repetition times of charging/discharging of a capacitor in the charge pump 13 for a unit time, is changed in accordance with the number of memory cells to be programmed, the variation of a time required for programming can be reduced. |
