Charge pump with improved high-swing cascode current source for accurate current matching in DPLL

Abstract

In loop dynamics of charge pump phase-locked loop, the charge pump current plays predominate role to loop bandwidth. Different charge pump architectures suffer from charge sharing, clock feed-through, channel charge injection, and current mismatch. Due to this, charge pump phase-locked loop can have more reference spur. Improved high-swing current source is proposed to obtain nearest current matching characteristics. 0.01% of current mismatch is achieved with 3.3 V, 90 nm CMOS technology. The circuit is verified at process voltage temperature corners.