Patent ID: 9252791
Filing Date: 2016-02-02
CPC Classification: H03L

Claim Text:
1. A phase-locked loop (PLL) system, comprising: a voltage reference generator with a generator control voltage output providing a fixed control voltage; a programmable voltage to current converter having a control voltage input, switch selection inputs, and a variable current output; a current-controlled oscillator (CCO) having an oscillator output providing an oscillator signal with an oscillating frequency and an input connected to the variable current output; a phase detector, coupled to the oscillator output, wherein in operation the phase detector generates an error signal based on an input reference signal frequency and a fraction of the oscillating frequency; a charge pump circuit connected to the phase detector, the charge pump circuit having a charge pump output that provides a charge pump control voltage based on the error signal; a switch module that selectively couples one of the generator control voltage output and the charge pump output to the control voltage input of the programmable voltage to current converter; and a controller with controller outputs coupled to the switch selection inputs and a further output coupled to a selection input of the switch module, wherein in operation the PLL system initially operates in an open loop configuration when the controller signals the switch module to couple the generator control voltage output to the control voltage input of the programmable voltage to current converter and when in the open loop configuration the controller selectively provides logic values to the switch selection inputs to adjust a frequency of the oscillator signal until a first condition is reached and thereafter the PLL system operates in a closed loop configuration when the controller signals the switch module to couple the charge pump output to the control voltage input of the programmable voltage to current converter.