VCO-based ADC with a simplified DAC for non-linearity correction Articles uri icon


  • GutiĆ©rrez, E.

publication date

  • June 2018


  • 54

International Standard Serial Number (ISSN)

  • 0013-5194

Electronic International Standard Serial Number (EISSN)

  • 1350-911X


  • The performance of open-loop ADCs implemented with VCOs is limited by VCO non-linearity and first-order noise shaping. The resolution limitation imposed by first-order noise shaping can be compensated by a ring oscillator VCO with many output phases. Linearity can also be improved by using a feedback loop around the VCO closed with a DAC. However, a long ring oscillator may require a DAC with a prohibitive number of bits if feedback is used to compensate distortion. This Letter proposes an ADC architecture based on the Leslie-Singh Sigma-Delta (Sigma Delta) modulator that allows to implement a distortion correction loop around a VCO with a simplified DAC of few levels, yet keeping a large number of output quantisation levels to maintain resolution. The Letter discusses the system-level architecture and shows an implementation circuit example to verify the effective correction of distortion.