Elmar Bach

A Difference Reference Voltage Buffer for ΔΣ-Converters

An open loop architecture for a reference voltage buffer in ΔΣ-converters is presented to achieve fast-settling, since the settling time of the references plays an important role in the global performance of sampled data converters. This design has been tested on a 2-1 ΔΣ-converter with an on-chip bandgap reference increasing the input related dynamic range up to 93.4 dB for a bandwidth of 99 kHz.

9.5 A 1.8V true-differential 140dB SPL full-scale standard CMOS MEMS digital microphone exhibiting 67dB SNR

Over the last few years, robust MEMS microphones have gained significant market share in consumer applications such as mobile phones and hearing aids. The consumer market is demanding improved quality for audio recording, while also being capable of suppressing high-energy disturbers, e.g., wind noise. The challenge is to achieve both high DR and SNR at low supply voltages that limit signal swing. Signal levels are expressed in dB Sound-Pressure-Level (dB SPL) with respect to the human hearing threshold at a sound pressure of 20µPa corresponding to 0dB SPL. Todays mass-market MEMS digital microphone solutions typically process sound up to 120dB SPL [1,2].

Readout circuits for silicon microphones

Silicon microphones have been established as a billion pieces per year market in the field of acoustic sensor technology. The main driving products for the large demand are mobile phones, tablet PCs, hearing aids, gaming consoles and camcorders. The consumer market is showing a clear need for increased performance to improve quality for voice-recognition and music recording. This requires a development of innovative low-power architectures for achieving a large signal-to-noise ratio along with processing of large sound pressure levels. This paper gives an introduction into the construction and architecture of a silicon microphone for consumer applications. An example of a readout circuit for processing of high sound pressure levels will be discussed.