Patent ID: 8638173
Filing Date: 2014-01-28
Classification: H03L

Abstract:
1. A method comprising: detecting that a control signal to an oscillator in a phase-locked loop (PLL) has exceeded a threshold while the PLL is locked to an input signal, wherein detecting that the control signal has exceeded the threshold includes: sending a calibration signal to a calibration circuit based on an output of the ADC; and in response to the detecting, adjusting an operating current of the oscillator to return the control signal below the threshold while maintaining lock of the PLL to the input signal, wherein adjusting the operating current includes slowly varying an output current of the calibration circuit coupled to the PLL to enable the PLL to maintain lock to the input signal during adjustment of the operating current, wherein adjusting the output of the calibration circuit includes adjusting an input current applied to a gate of a first transistor, wherein the gate of the first transistor is coupled to a gate of a second transistor via a resistive element, and wherein a current steering circuit generates a feedback current to partially offset the input current based on a voltage difference across the resistive element.