A Counting Based Bridge to Digital Converter Achieving a Walden FoM of 0.048 nJ/Conv-Step

This paper presents a counting based BDC for environmental monitoring based IoT applications, where the ramp is generated with a compact and power efficient switched capacitor DAC. This DAC is realized using a single switched capacitor resistor, eliminating the source of any mismatch. The BDC is fabricated in 65 nm CMOS and occupies an area of 0.014 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>. It has a wide input range of 830 mV and achieves an SNR of 49.97 dB and 65.6 dB, for dynamic and static inputs respectively. The BDC consumes <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$30 \mu \mathrm{A}$</tex> with a 0.41 ms conversion time, resulting in a Walden FoM of 0.048 n.J/Conv-step.