Design of a low-mismatch gain-boosting charge pump for phase-locked loops

A modified technique to enhance current matching in charge pumps (CP), employed in phase-locked loops, is proposed. In addition to gain-boosting, used to increase the output impedance of the CP, a low-voltage cascode current mirror is used to enhance current matching over process corners. A good matching between the two current sources of the CP can be achieved with current mismatch equals to 0.6% in typical conditions and 1% over all process variations. The CP output compliance voltage range of 0.3-2.2 V is achieved for 2.5-V supply using the I/O devices of a 90-nm technology.