Design considerations for autocalibrations of wide-bandδ∑ fractional- N PLL synthesizers

Autocalibration of vco frequency and loop gain is an essential process in pll frequency synthesizers. in a wide tuning-range fractional- n pll frequency synthesizer,high-speed and high-precision automatic calibration is especially important for shortening the lock time and improving the phase noise. this paper reviews the design issues of the pll auto-calibration and discusses on the limitations of the previous techniques. a very simple and efficient auto-calibration method based on a high-speed frequency-to-digital converter (fdc) is proposed and verified through simulations. the proposed method is highly suited for a very wide-band fractional- n pll. © 2011 jaewook shin and hyunchol shin.