Abstract
An all-digital phase-locked loop (ADPLL) with a multiphase digitally controlled oscillator (DCO) incorporating the bootstrapped and interpolated schemes is proposed in this paper. The bootstrapped ring oscillator can boost the output voltage to a higher level than the supply voltage. Thus, the oscillator can be operated in low-supply-voltage applications. MOS varactor is used in the bootstrapped capacitor to reduce the area cost. Circuit analysis and simulated verification were performed for an optimized design. The interpolated DCO has multiphase outputs and a high operating frequency. The test chip was implemented in a 90-nm CMOS process, and the core area was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$60\times 117\,\,\mu \text{m}^{2}$ </tex-math></inline-formula> . The power consumptions at 1160 MHz and 20 MHz were <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$912.6~\mu \text{W}$ </tex-math></inline-formula> (at 0.6 V) and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.94~\mu \text{W}$ </tex-math></inline-formula> (at 0.2 V), respectively. In the worst-case jitter performance, the root mean square (RMS) jitters were less than 0.42%.
Highlights
Low-supply-voltage phase-locked loops (PLLs) using several digital, analog, and charge pump schemes have been proposed for low-power and high-frequency applications
We examined the all-digital phase-locked loop (ADPLL) design parameters for a voltage supply range of 0.2 V and 0.6 V
A low-supply-voltage and multiphase ADPLL is proposed in this study
Summary
Low-supply-voltage phase-locked loops (PLLs) using several digital, analog, and charge pump schemes have been proposed for low-power and high-frequency applications. In the proposed multiphase DCO, a ring oscillator with the interpolator scheme and bootstrapped techniques were used to extend the maximum operating frequency in the supply voltage range of 0.2–0.6 V.
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