Title :
An accurate analytical spur model for an integer-N phase-locked loop
Author :
Kamal, Nabeel ; Al-Sarawi, Said ; Abbott, Derek
Author_Institution :
Sch. of Electr. & Electron. Eng., Univ. of Adelaide, Adelaide, SA, Australia
Abstract :
Reference spur is a limiting performance factor in an integer-N phase-locked loop (PLL). In this paper, we investigate the effect of VCO gain, ripple magnitude in VCO tuning voltage and reference frequency with reference spur magnitude. Normally, VCO gain and reference frequency are chosen according to needed system requirement, leaving only the ripple voltage on the VCO control signal to be minimised in order to minimize the reference spur. The ripple voltage is mainly contributed by current mismatch, current leakage, switching delay and discrepancies between the rise and fall times in charge pump circuit. In addition, loop filter is also affecting the ripple voltage. In this paper, we consider these effects analytically to predict ripple voltage in the VCO tuning voltage and hence calculate the reference spur magnitude of the PLL device.
Keywords :
charge pump circuits; phase locked loops; voltage-controlled oscillators; PLL device; VCO control signal; VCO gain; VCO tuning voltage; analytical spur model; charge pump circuit; current leakage; current mismatch; fall time; integer-N PLL; integer-N phase-locked loop; loop filter; reference frequency; reference spur magnitude; ripple magnitude; ripple voltage; rise time; switching delay; Charge pumps; Delay; Equations; Mathematical model; Phase locked loops; Tuning; Voltage-controlled oscillators; charge pump; current mismatch; loop filter; phase/frequency detector (PFD); reference spur; tuning voltage; voltage controlled oscillator (VCO);
Conference_Titel :
Intelligent and Advanced Systems (ICIAS), 2012 4th International Conference on
Conference_Location :
Kuala Lumpur
Print_ISBN :
978-1-4577-1968-4
DOI :
10.1109/ICIAS.2012.6306096