A 399uW 114.3 dB DR Companding Readout ASIC for MEMS Microphones Employing a Multirate Time-Domain ADC

Javier Granizo; Ruben Garvi; Ricardo Carrero; Jorge de la Torre; Javier Fernandez; Dietmar Straeussnigg; Andreas Wiesbauer; Luis Hernandez

arXiv · 2606.17879

A 399uW 114.3 dB DR Companding Readout ASIC for MEMS Microphones Employing a Multirate Time-Domain ADC

Javier Granizo·Ruben Garvi·Ricardo Carrero·Jorge de la Torre·Javier Fernandez·Dietmar Straeussnigg·Andreas Wiesbauer·Luis Hernandez

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Abstract

Improvements in the dynamic range and sensitivity of digital MEMS microphones are essential in applications like advanced noise canceling and voice recognition. A cost effective solution to achieve these goals is the companding ADC architecture. Companding ADCs split the dynamic range in several segments with different quantization noise levels, relaxing power constraints. A common problem of companding microphones are audible artifacts generated when the input signal crosses the boundaries between different amplitude segments. We show in this paper a companding ADC architecture that mitigates the boundary artifacts by leveraging the instantaneous and high-resolution time-domain representation of the input signal in a VCO-based ADC. The use of a multi-rate frequency-to-digital converter allows to decouple quantization noise from the VCO frequency, keeping standard audio sampling rates. Co-optimization of the driver and oscillator circuits enables our VCO-ADC to reach \textgreater 112dBc of peak SFDR without a feedback DAC, keeping a Giga-Ohm input impedance compatible with a capacitive MEMS. We show measurements of a 0.13 $\mu$m ASIC implementing a complete readout circuit for a digital MEMS microphone. This includes two analog channels and the digital signal processing and calibration blocks required to deliver a standard single-bit PDM output. This ADC reaches a dynamic range of 114.3dB with a power budget under 400 uW, a Schreier FoM_{SNDR} of 171.0 dB and a FoM_{DR} of 191.3 dB.

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BibTeX RIS

Javier Granizo, Ruben Garvi, Ricardo Carrero, Jorge de la Torre, Javier Fernandez, Dietmar Straeussnigg, Andreas Wiesbauer, Luis Hernandez. 2026-06-16. A 399uW 114.3 dB DR Companding Readout ASIC for MEMS Microphones Employing a Multirate Time-Domain ADC. https://arxiv.org/abs/2606.17879

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