A 0.96mA quiescent current, 0.0032% THD+N, 1.45W Class-D audio amplifier with area-efficient PWM-residual-aliasing reduction

Shih Hsiung Chien, Yi Wen Chen, Tai Haur Kuo

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)

Abstract

Low quiescent current (IQ) is critical for Class-D audio amplifiers in mobile devices to extend battery usage time [1], since typical audio signals have a high crest factor of 10 to 20dB. In addition, low distortion is also important for audio fidelity. Distortion sources in closed-loop Class-D amplifiers can be classified into two types. One is attributed to the nonlinearities of PWM modulators and power stages, while the other is due to the aliasing of fed-back PWM high-frequency residuals, the latter of which comprises phase-error and duty-cycle-error distortions [2]. Figure 3.6.1 shows 2nd-order closed-loop amplifiers and existing techniques for enhancing an amplifier's linearity. Increasing the loop filter order to obtain a higher in-band loop gain by using more integrators [3] or the single-amplifier-biquad [4] suppresses all aforementioned distortions except for the phase-error distortion, which can be suppressed by adding a phase-error-free PWM modulator [2]. However, these techniques increase IQ and/or die area due to the additional active circuits and/or several resistors and capacitors. Since phase-error distortion, as well as duty-cycle-error distortion, is caused by the fed-back PWM high-frequency residuals aliasing with the reference triangular wave VTRI, a uniform PWM [5] with a sample-and-hold circuit implemented before the PWM modulation reduces the PWM residuals via an equivalent notch filtering. However, loop stability is affected by the notch filtering unless the PWM switching frequency fSW is increased, but doing so increases power consumption [4]. Though the technique in [1] uses a feed-forward path with a replicated loop filter to eliminate the PWM residuals without affecting loop stability, the replicated loop filter increases both IQ and area.

Original languageEnglish
Title of host publication2018 IEEE International Solid-State Circuits Conference, ISSCC 2018
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages60-62
Number of pages3
ISBN (Electronic)9781509049394
DOIs
Publication statusPublished - 2018 Mar 8
Event65th IEEE International Solid-State Circuits Conference, ISSCC 2018 - San Francisco, United States
Duration: 2018 Feb 112018 Feb 15

Publication series

NameDigest of Technical Papers - IEEE International Solid-State Circuits Conference
Volume61
ISSN (Print)0193-6530

Other

Other65th IEEE International Solid-State Circuits Conference, ISSCC 2018
CountryUnited States
CitySan Francisco
Period18-02-1118-02-15

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All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering

Cite this

Chien, S. H., Chen, Y. W., & Kuo, T. H. (2018). A 0.96mA quiescent current, 0.0032% THD+N, 1.45W Class-D audio amplifier with area-efficient PWM-residual-aliasing reduction. In 2018 IEEE International Solid-State Circuits Conference, ISSCC 2018 (pp. 60-62). (Digest of Technical Papers - IEEE International Solid-State Circuits Conference; Vol. 61). Institute of Electrical and Electronics Engineers Inc.. https://doi.org/10.1109/ISSCC.2018.8310183