A 2.4-GHz 1.5-mW Digital Multiplying Delay-Locked Loop Using Pulsewidth Comparator and Double Injection Technique

Abstract

In this paper, we propose a low-jitter low-power digital multiplying delay-locked loop (MDLL) with a self-calibrated double reference injection scheme. To reduce jitter, the noisy edge of the oscillator is replaced by both the rising and falling edges of the clean reference, which results in 6-dB reduction in phase noise compared with a conventional single-edge injection MDLL. Reference spur caused by a frequency error of the oscillator, duty-cycle error of the reference, and circuit imperfection, such as offset and mismatch, is removed by employing three background feedback loops with a shared analog pulsewidth comparator. Implemented in 28-nm CMOS, the proposed digital MDLL generates 2.4-GHz clock and achieves a spur of −51.4 dBc and an rms jitter of 699 ${\mathrm{ fs}}_{\mathrm{ rms}}$ while consuming 1.5 mW from 1-V supply.