A 16mW 78dB-SNDR 10MHz-BW CT-ΔΣ ADC using residue-cancelling VCO-based quantizer

Karthikeyan Reddy, Sachin Rao, Rajesh Inti, Brian Young, Amr Elshazly, Mrunmay Talegaonkar, Pavan Kumar Hanumolu

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Voltage-controlled oscillator (VCO) based analog-to-digital conversion presents an attractive means of implementing high-bandwidth oversampling ADCs [1,2]. They exhibit inherent noise-shaping properties and can operate at low supply voltages and high sampling rates [1-3]. However, usage of VCO-based ADCs has been limited due to their nonlinear voltage-to-frequency (V-to-F) transfer characteristic, which severely degrades their distortion performance. Digital calibration is used to combat nonlinearity in an open-loop VCO-based ADC, but 1 st-order noise-shaping mandates high OSRs, thus increasing power dissipation in digital circuits, even in a nanometer-scale CMOS process [1]. In [2], nonlinearity is suppressed by embedding the VCO in a ΔΣ loop. While this technique works in principle, the need for large loop gain at high frequencies makes it very difficult to achieve high SNDR. For instance, the suppression level near the band edge is approximately 20dB for a VCO-based 2 nd-order modulator operating with an over-sampling ratio (OSR) of 30. Our ADC overcomes the impact of VCO non-linearity by minimizing the input signal processed by the VCO. The prototype achieves 78.3dB SNDR in a 10MHz signal bandwidth at 600MHz sampling rate, while consuming 16mW power.

Original languageEnglish (US)
Title of host publication2012 IEEE International Solid-State Circuits Conference, ISSCC 2012 - Digest of Technical Papers
Number of pages2
StatePublished - 2012
Externally publishedYes
Event59th International Solid-State Circuits Conference, ISSCC 2012 - San Francisco, CA, United States
Duration: Feb 19 2012Feb 23 2012

Publication series

NameDigest of Technical Papers - IEEE International Solid-State Circuits Conference
ISSN (Print)0193-6530


Other59th International Solid-State Circuits Conference, ISSCC 2012
Country/TerritoryUnited States
CitySan Francisco, CA

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering


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