A 155 /spl mu/W 88-dB DR Discrete-Time /spl Delta/ /spl 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.