A 155µW 88-dB DR discrete-time delta-sigma modulator for digital hearing aids exploiting a summing SAR ADC Quantizer

This paper presents a low-power switched-capacitor $Delta Sigma$ modulator for digital hearing-aid applications that features a novel summing successive approximation (SAR). The summing SAR performs multi-bit quantization together with the analog addition required in feed-forward (FF) $Delta Sigma$ modulator $(Delta Sigma {rm M})$ topologies, with no attenuation of the input signals and no need for amplifiers. The prototype is implemented in a 0.18-$mu$ m CMOS technology and its measurements demonstrate a dynamic range of 88 dB in 10 kHz bandwidth while consuming 155 $mu$W from a 1.8 V supply. The combined use of passive addition and SAR quantization reduces the complexity and power consumption of the modulator. The summing SAR ADC quantizer results in a calculated power saving of 40% when compared to a multi-bit FF $Delta Sigma$M using active addition and flash quantization.