Adaptive bandwidth PLL with compact current mode filter

This paper presents a compact self-biased current-mode filter (CMF) PLL architecture, which uses relative ratio of charge-pump currents (I/sub cp2/ / |I/sub cp2/-I/sub cp1/|) to obtain a capacitor multiplier. Compatible with self-biased CMF, a modified charge pump switches structure is proposed to reduce phase offset and current activating time. The whole PLL has been designed and implemented in a 0.25 /spl mu/m CMOS process. The simulated PLL provides the loop parameters almost independent of divider multiplication factor, and decreases the capacitance to 1/10 of conventional one, and the results also shows it reduces the acquisition time by a factor of about 3.