Low jitter tunable voltage control oscillator with self calibration circuits to reduce chip fabrication process variation

摘要

A voltage controlled oscillator (VCO) which can be configured with a smaller tuning range than is ordinarily required is presented. Ordinarily, the tuning range is selected much broader than the application warrants so that sufficient range is still provided despite VCO process variations. The inventive VCO is able to substantially eliminate the effects of process variation by utilizing a calibration circuit and process, so that variation in VCO device operation is minimized despite substantial process variation. Accordingly, the inventive VCO device is subject to reduced levels of jitter as its range need not be utilized for overcoming process variation arising during device fabrication.

主权项

1. A voltage controlled oscillator (VCO) apparatus, comprising:
a ring oscillator comprising multiple digital stages of current mode logic (CML) inverters to generate an oscillation frequency; a resistor emulator that emulates an external resistor device which is constant despite fabrication process variation; a self calibration controller circuit that in its calibration mode adjusts resistance provided by said resistor emulator to create a RC delay in said current mode logic (CML) inverters according to target running frequency of said VCO apparatus; an amplifier configured for amplifying an input control voltage to the VCO and outputting a first control voltage to said ring oscillator; and an adaptive bias current generator circuit configured for adjusting bias current by providing a second control voltage to said ring oscillator, said adaptive bias current generator performs automatic feedback control based on said resistor emulator and input control voltage of VCO to control both frequency and output swing of said ring oscillator; whereby said VCO apparatus generates a frequency output proportional to said input control voltage with reduced impact from fabrication process variation.