A 320MHz–2.56GHz low jitter phase-locked loop with adaptive-bandwidth technique

This paper presents a novel adaptive-bandwidth phase-locked loop (PLL) using a closed loop voltage controlled oscillator (VCO). The adaptive-bandwidth PLL uses the gain of closed loop VCO to obtain a constant unity gain bandwidth over an operating frequency range. Furthermore, a charge pump (CP) current is proportional to the current of VCO so that CP current is in proportion to the VCO frequency. Since the adaptive-bandwidth is optimized over the VCO frequency, an integrated RMS jitter is reduced in comparison to a conventional fixed-bandwidth PLL. We simulate the proposed PLL in 130 nm CMOS technology at 1.2 V power supply. The integrated RMS jitter of the proposed adaptive-bandwidth PLL is 2.35 psec which is 70% smaller than the conventional PLL. This adaptive-bandwidth PLL consumes 2.6 mW at 2.56 GHz output frequency.