Conventional CMOS charge-pump circuits have some current mismatch problems. The current mismatch induces a phase offset which deteriorates the performance of PLLs or DLLs. This paper investigates causes of current mismatch of conventional CMOS charge-pump and proposes new charge-pump circuits to reduce the current mismatch. The DLL with proposed charge-pump is simulated in a 0.18μm CMOS process.
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