Journal of Computations & Modelling
Modified gain boosting charge pump for low current mismatch and high performance phase-lock loop
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In conventional CMOS charge pump circuits there are some current mismatching characteristics which result in a phase offset in phase-locked loop circuits. This paper presents a new charge pump circuit after scrutinizing the deeper examination of the existing current mismatch problem. It combines an error amplifier with reference current sources to achieve good current matching characteristics and lower phase noises, and at the same time it can eliminate charge sharing by using charge removal transistors. 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 of the CP is achieved with current mismatch equals to 0.6% in typical conditions and 1% over all process variations. The CP output compliance voltage range of 0.1-1.8 V is achieved for 1.8-V supply voltage. The circuit was designed using 0.18um TSMC CMOS technology and simulated by Spectre tools.