Near-threshold charge pump circuit using dual feedback loop

A near-threshold charge pump circuit suitable for a phase-locked loopbased frequency synthesiser is presented. The charge pump uses gate switches and dual feedback loops to achieve good up/down current matching characteristics in low-voltage operation. The applied gate switches reduce the leakage current and the feedback loops provide a more stable operation. Post-layout simulation results demonstrate that the proposed charge pump circuit consumes only 60 μW with a 0.5 V supply voltage. The charge pump circuit is implemented in a 0.13 μm CMOS process.