A charge-pump with a high output swing for PLL and CDR applications

In this paper, a technique to improve the output swing of the charge pump (CP) block is introduced. CPs are one of the important building blocks of phase-locked loops (PLLs) and PLL-based clock and data recovery (CDR) systems. The proposed feedback-based approach ensures that the currents of the two current sources in the CP maintain their values over an extended range of the charge-pump output voltage. This current stabilization is achieved by adjusting the control voltage of the charge pump current sources. A proof-of-concept charge pump is designed and simulated in a 0.13 μm CMOS process and achieves an output swing of 1.16 V while operating from a 1.2-V supply. The power overhead of the added feedback loop is 3%. The designed charge pump is also used in a complete phase-locked loop circuit to confirm its operation and effectiveness.