A LUT-based Background Linearization Technique for VCO-based ADC Employing $K_{\text{VCO}}-\text{Locked}-\text{Loop}$

This paper proposes a look-up-table (LUT)-based background calibration to improve the linearity of the ring voltage-controlled oscillator (VCO)-based analog-to-digital converter (ADC). The nonlinearity of the tuning gain $(\boldsymbol{K}_{\mathbf{VCO}})$ of the VCO is considered as that there is an individual $\boldsymbol{K}_{\mathbf{VCO}}(\boldsymbol{K}_{\mathbf{VCOI}})$ for each ADC output level. The $\boldsymbol{K}_{\mathbf{VCO}}-\mathbf{Locked}-\mathbf{Loop}$ (KLL) is employed to force the $\boldsymbol{K}_{\mathbf{VCOI}}\mathbf{s}$ to the same reference value, thus eliminating the nonlinearity. The effectiveness of the KLL-assisted linearization scheme is not affected by the matching property of the technology and the characteristics of ADC input signal. Thanks to the KLL-assisted calibration, the total harmonic distortion is suppressed by 37.8dB with the required ADC output samples of 2 ¹⁸ , achieving a fast linearization process.