Patent ID: 6894554
Filing Date: 2005-05-17
Classification: G05F

Abstract:
1. A step-up circuit comprising: a step-up clock signal generation device that generates a clock signal to be used for voltage step-up; at least one step-up stage that steps up a power supply voltage based on the clock signal; and a control device that, after starting an operation, changes a frequency of the clock signal to be supplied to the step-up stage from a value lower than a normal value to the normal value, wherein the control device includes: a plurality of frequency-divider circuits that frequency-divide the clock signal generated by the step-up clock signal generation device, and respectively output a plurality of divided clock signals having different frequency division ratios, a selector circuit that selects, based on a control signal, one of the clock signal and the plurality of frequency-divided clock signals, and a counter that counts the clock signal selected by the selector circuit to thereby generate the control signal; and wherein the step-up stage steps up the power supply voltage based on the clock signal selected by the selector circuit.