Charge pump circuit having switching circuits for reducing leakage currents

Abstract

To reduce leakage current from a current source transistor in a charge pump circuit of a PLL circuit, the charge pump circuit is activated according to an up signal or a down signal generated according to whether the phase of a clock output from VCO is faster or slower than that of a reference clock for generating current for charging or discharging an LPF that supplies input to VCO of the disclosed PLL circuit. The charge pump circuit is composed of a first current source transistor for generating current for charging LPF, a first switching transistor for connecting the first current source transistor to a power source according to an up signal, a second current source transistor for generating current for discharging LPF and a second switching transistor for grounding the second current source transistor according to a down signal, and bias is applied to the first and second current source transistors when the charge pump circuit is inactivated.