A 2.9-GHz LC-VCO based PLL with a fast automatic frequency control

Abstract

A 2.9-GHz LC-VCO based PLL with a fast automatic frequency control (AFC) circuit is proposed. The fast AFC function is achieved by a fourfold reference frequency multiplication and a binary searching algorithm in a 4-bit capacitor array of an LC-VCO and completed in 4-cycles of the reference signal. The simulation results for the proposed PLL designed in a CMOS 130 nm process, show that an AFC time of only 100 ns, operation frequencies of 2.14 to 2.95 GHz, and a phase noise of -125 dBc/Hz at 1 MHz offset, while dissipating 4.9 mA at a 1.2-V supply.