A novel differential VCO circuit design for USB hub

The paper describes a novel differential voltage controlled oscillator circuit, which is used in the phase locked loop of a USB hub chip. The output clock signals can be altered from 36MHz to 96MHz by changing the value of control signals. The voltage controlled oscillator architecture, module circuits of voltage controlled oscillator design, simulation results, and chip layout are included. Experimental results using CSMC 0.6/spl mu/m process technology show that the anticipatory performance can be obtained and the voltage controlled oscillator circuit consumes only 0.9 mW from a 5V power supply.