A 78.2nW 3-channel time-delay-to-digital converter using polarity coincidence for audio-based object localization

This paper presents an ultra-low-power intersignal time-delay-to-digital converter. It introduces polarity-coincidence adaptive time-delay estimation, a mixed-signal processing technique that consumes only 78.2nW for a 3-channel delay estimation. A 0.18um CMOS implementation of the converter has been tested and characterized with controlled and real-life stimuli. This analog-to-feature converter has further been used to estimate the time difference of arrival in an audio-based vehicle-bearing IoT system.