Patent ID: 8519757
Filing Date: 2013-08-27
Classification: H03L

Abstract:
1. An apparatus for frequency calibration in a frequency synthesizer, the frequency synthesizer comprising a phase detector for detecting a phase difference between a phase of an input frequency and a phase of a feedback frequency being fed back by a programmable divider, and a charge pump for generating and outputting one of a step-up voltage and a step-down voltage to a voltage-controlled oscillator via a loop filter, the apparatus for frequency calibration in the frequency synthesizer comprising: a frequency comparator, comparing a current frequency with a target frequency while the programmable divider feeds an output frequency of the voltage-controlled oscillator back to the phase detector; a memory bank selector, selecting a voltage-controlled oscillator memory bank of the voltage-controlled oscillator to reach the target frequency; and an up/down processor disposed between the phase detector and the charge pump, the up/down processor controlling the charge pump to output one of a GND voltage and a VDD voltage in an open loop status, and to output one of the step-up voltage and the step-down voltage in a close loop status according to the phase difference, wherein a value of the memory bank which is selected by the memory bank selector in the open loop status is added to an offset to determine a final value of the voltage-controlled oscillator memory bank.