A 4.4μW 2.5kHz-BW 92.1dB-SNDR 3rd-Order VCO-Based ADC With Pseudo Virtual Ground Feedforward Linearization | IEEE Conference Publication | IEEE Xplore

A 4.4μW 2.5kHz-BW 92.1dB-SNDR 3rd-Order VCO-Based ADC With Pseudo Virtual Ground Feedforward Linearization


Abstract:

The rise of the internet-of-things and distributed sensor nodes with machine-learning and edge processing are driving the need for low-power, high-precision ADCs. These h...Show More

Abstract:

The rise of the internet-of-things and distributed sensor nodes with machine-learning and edge processing are driving the need for low-power, high-precision ADCs. These highly digital systems are best implemented in advanced process nodes that have low intrinsic gain and low supply voltages, making the design of the high-performance amplifiers required in high-precision delta-sigma (ΔΣ) ADCs challenging. Time-domain ADC architectures, such as voltage-controlled oscillator (VCO)-based ADCs, have been explored to address these challenges as time-domain processing is agnostic to supply voltage and benefits from advanced process nodes with faster switching times [1]. However, linearity has been challenging as open-loop VCO-based ADCs have only ~50dB SFDR. As such, significant research has been devoted to the development of linearization techniques such as feedback [1], mixed-domain operation [2], digital calibration [3], and higher-order noise-shaping using VCO-only architectures [4]. This paper presents a 3rd-order, VCO-only ΔΣ ADC achieving 92.1dB SNDR over a 2.5kHz bandwidth (BW) using a pseudo virtual ground feedforward (PVG FF) technique. The key concept is to feed forward the pseudo virtual ground in a capacitively coupled VCO-based ADC, which linearizes and stabilizes the system while only using a single feedback DAC. This approach enables a high dynamic range (DR) due to the 3rd-order noise-shaping and >120dB SFDR due to the linearization. The prototype ADC consumes 4.4μW from a 0.8V supply achieving the best-reported SNDR Schreier figure of merit (FoM) for VCO-based ADCs at 179.6dB.
Date of Conference: 20-26 February 2022
Date Added to IEEE Xplore: 17 March 2022
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Conference Location: San Francisco, CA, USA

References

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