A 1.8 V ΔΣ modulator interface for electret microphone with on-chip reference

The design of a power-efficient second-order / modulator for voice-band is presented. At system level, a new single-loop, single-stage modulator is proposed. The modulator employs only one class-AB op-amp to realize a second-order noise shaping for voice-band applications. The modulator is designed in a 0.25 µm standard CMOS process, and exhibits 86 dB dynamic range (DR) for a 4 kHz voicebandwidth. The proposed modulator consumes 125 µW from a 2.5 V supply.

Section: Resultsmentioning

confidence: 73%

A low-power, second-order Δ/Σ modulator using a single class-AB op-amp for voice-band applications

Safarian

Sahandiesfanjani²,

Heydari

et al. 2006

“…1(a). The readout interface chip can be packaged in an electret microphone capsule or integrated on the same chip with a micro-electro-mechanical-system (MEMS) microphone, where the microphone's weak analog output signal directly enters the readout interface, so that the microphone capsule will have a digital output externally [1][2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

A microphone readout interface with 74-dB SNDR

Odame

2014

A continuous-time (CT) sigma-delta modulator (SDM) for condenser microphone readout interfaces is presented in this paper. The CT SDM can accommodate a single-ended input and has high input impedance, so that it can be directly driven by a single-ended condenser microphone. A current-sensing boosted OTA-C integrator with capacitive feedforward compensation is employed in the CT SDM to achieve high input impedance and high linearity with low power consumption. Fabricated in a 0:35-lm complementary metal-oxide-semiconductor (CMOS) process, a circuit prototype of the CT SDM achieves a peak signal-to-noise-and-distortion ratio of 74.2 dB, with 10-kHz bandwidth and 801-lW power consumption.

“…The demand for continuous miniaturization and performance improvement of such systems calls for the development of new devices, both on the transducer and on the interface circuit side [1][2][3][4][5]. As a consequence, conventional devices, such as condenser or electret microphones are giving way to MEMS transducers [6][7][8] and novel read-out architectures are being developed to match MEMS microphone specifications [9,10].…”

Section: Introductionmentioning

confidence: 99%

A 1.0-mW, 71-dB SNDR, fourth-order ΣΔ interface circuit for MEMS microphones

Picolli

Grassi

Fornasari³

et al. 2010

In this paper an integrated interface circuit for condenser MEMS microphones is presented. It consists of an input buffer followed by a multi-bit (12-levels), analog, second-order RD modulator and a fully-digital, single-bit, fourth-order RD modulator, thus providing a single-bit output signal with fourth order noise shaping, compatible with standard audio chipsets. The circuit, supplied with 3.3 V, exhibits a current consumption of 215 lA for the analog part and 95 lA for the digital part. The measured signal-to-noise and distortion ratio (SNDR) is 71 dB, with an input signal amplitude as large as -1.8 dB with respect to full-scale, obtained thanks to the use of a feed-forward architecture in the analog RD modulator, which relaxes the voltage swing requirements of the operational amplifiers. The test chip, fabricated in a 0.35-lm CMOS process, occupies an area of 3 mm 2 , including pads.