Spread spectrum clock generation circuit and a method of controlling thereof

Abstract

A spread spectrum clock generation circuit and a controlling method thereof are disclosed, which provide clocks having less jitter and ideal spread spectrum and enable a reduction in circuit scale and in power consumption. To this end, a current control type modulatoris equipped with a current source Ia (current). A charger unit CGa and a discharger unit DGa are designed such that currents i,andare allowed to flow, for example, by properly setting the sizes of transistors. Modulation cycles CIa to CIIIa are repeated and an output code is generated from a switching control circuitaccording to each modulation cycle. A switching unit SSa is controlled according to the output code, thereby charging or discharging a capacitor element Cwith a charge/discharge current CDI corresponding to the output code. Hence, charge amounts and discharge amounts for all the modulation cycles CIa to CIIIa have the same value, i.e.,[A·clock].