Patent ID: 7705641
Filing Date: 2010-04-27
Classification: H03L

Abstract:
1. A charge pump for a phase-locked loop circuit, the charge pump comprising: a sourcing current transistor providing a sourcing current, wherein the sourcing current transistor is coupled to a high-voltage operating voltage supply; a sourcing control circuit coupled to the sourcing current transistor, the sourcing control circuit using low-voltage sourcing control signals at a low voltage to selectively cause the charge pump to source the sourcing current to an output of the charge pump, wherein the low-voltage sourcing control signals have not been level shifted in voltage level to a higher voltage than the low voltage to selectively cause the charge pump to source the sourcing current, and wherein the sourcing control circuit includes a plurality of PMOS transistors forming a sourcing switch used for steering the current flow either to an output of the charge pump or to ground based on the sourcing control signals; and a sinking control circuit coupled to one or more sinking current transistors, the current sinking control circuit using low-voltage sinking control signals at a low voltage to selectively cause the charge pump to sink the sinking current from the output of the charge pump, wherein the low-voltage sinking control signals have not been level shifted in voltage level to a higher voltage than the low voltage to selectively cause the charge pump to sink the sinking current, and wherein the sinking control circuit includes a plurality of PMOS transistors forming a sinking switch used for steering the current flow either to ground or to the one or more sinking transistors based on the sinking control signals.