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A digital input class-D audio amplifier with sixth-order PWM

Shumeng Luo1 and Dongmei Li2,

+ Author Affiliations

 Corresponding author: Li Dongmei, ei@tsinghua.edu.cn

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Abstract: A digital input class-D audio amplifier with a sixth-order pulse-width modulation (PWM) modulator is presented. This modulator moves the PWM generator into the closed sigma-delta modulator loop. The noise and distortions generated at the PWM generator module are suppressed by the high gain of the forward loop of the sigma-delta modulator. Therefore, at the output of the modulator, a very clean PWM signal is acquired for driving the power stage of the class-D amplifier. A sixth-order modulator is designed to balance the performance and the system clock speed. Fabricated in standard 0.18 μm CMOS technology, this class-D amplifier achieves 110 dB dynamic range, 100 dB signal-to-noise rate, and 0.0056% total harmonic distortion plus noise.

Key words: PWMclass-D digital audiosigma-delta



[1]
Minsheng W, Xicheng J, Jungwoo S, et al. A 120 dB dynamic range 400 mW class-D speaker driver with fourth-order PWM modulator. IEEE J Solid-State Circuits, 2010, 45(8):1427 doi: 10.1109/JSSC.2010.2047426
[2]
Guanziroli F, Bassoli R, Crippa C, et al. A 1 W 104 dB SNR filter-less fully-digital open-loop class D audio amplifier with EMI reduction. IEEE J Solid-State Circuits, 2012, 47(3):686 doi: 10.1109/JSSC.2011.2178930
[3]
Lee Y H, Seok C K, Kim B J, et al. A 1.3 mW per-channel 103-dB SNR stereo audio DAC with class-D head-phones amplifier in 65 nm CMOS. IEEE Symposium on VLSI Circuits, 2008 http://ieeexplore.ieee.org/document/4585996/
[4]
Berkhout M, Dooper L. A 3.4 W digital-in class-D audio amplifier. Proceedings of the ESSCIRC, 2011
[5]
Ramaswamy S, Krishnan J, Forejt B, et al. A high-performance digital-input class-D amplifier with direct battery connection in a 90nm digital CMOS process. Digest of Technical Papers, IEEE International Solid-State Circuits Conference, 2008:436 http://ieeexplore.ieee.org/document/4523244/
[6]
Teplechuk M A, Gribben T, Amadi C. True filterless class-D audio amplifier. IEEE J Solid-State Circuits, 2011, 46(12):2784 doi: 10.1109/JSSC.2011.2162913
[7]
Gaalaas E, Liu B Y, Nishimura N. Integrated stereo delta-sigma class D amplifier. Digest of Technical Papers, IEEE International Solid-State Circuits Conference, 2005:120 http://ieeexplore.ieee.org/document/1493898/
[8]
Goldberg J M, Sandler M B. New high accuracy pulse width modulation based digital-to-analogue convertor/power amplifier. IEE Proceedings Circuits, Devices and Systems, 1994, 141(4):315 doi: 10.1049/ip-cds:19941102
[9]
Nielsen K, Olufsen B, Denmark. A review and comparison of pulse width modulation (PWM) methods for analog and digital input switching power amplifiers. AES E-Library, 1997, 102:4446 http://www.aes.org/e-lib/browse.cfm?elib=7333
[10]
Berkhout M, Dooper L. Class-D audio amplifiers in mobile applications. IEEE Trans Circuits Syst Ⅰ:Regular Papers, 2010, 57(5):992 doi: 10.1109/TCSI.2010.2046200
[11]
Berkhout M. An integrated 200-W class-D audio amplifier. IEEE J Solid-State Circuits, 2003, 38(7):1198 doi: 10.1109/JSSC.2003.813238
Fig. 1.  Typical architecture of a true digital class-D amplifier.

Fig. 2.  The comparison of PDM and PWM.

Fig. 3.  A kind of digital class-D audio amplifier architecture.

Fig. 4.  (a) Architecture of a class-D amplifier with PWM modulator. (b) Model of a PWM modulator.

Fig. 5.  Error-feedback structure.

Fig. 6.  The architecture of the PWM modulator.

Fig. 7.  The comparison of the original NTF, the NTF of the modulator, and the quantized NTF of the modulator.

Fig. 8.  The power spectral density (PSD) of the output of the PWM modulator.

Fig. 9.  The power stage of the amplifier.

Fig. 10.  The picture of the amplifier.

Fig. 11.  Measured PSD for 1.001 kHz sine waves.

Fig. 12.  Measured SNDR and power efficiency.

Table 1.   Performance comparison.

[1]
Minsheng W, Xicheng J, Jungwoo S, et al. A 120 dB dynamic range 400 mW class-D speaker driver with fourth-order PWM modulator. IEEE J Solid-State Circuits, 2010, 45(8):1427 doi: 10.1109/JSSC.2010.2047426
[2]
Guanziroli F, Bassoli R, Crippa C, et al. A 1 W 104 dB SNR filter-less fully-digital open-loop class D audio amplifier with EMI reduction. IEEE J Solid-State Circuits, 2012, 47(3):686 doi: 10.1109/JSSC.2011.2178930
[3]
Lee Y H, Seok C K, Kim B J, et al. A 1.3 mW per-channel 103-dB SNR stereo audio DAC with class-D head-phones amplifier in 65 nm CMOS. IEEE Symposium on VLSI Circuits, 2008 http://ieeexplore.ieee.org/document/4585996/
[4]
Berkhout M, Dooper L. A 3.4 W digital-in class-D audio amplifier. Proceedings of the ESSCIRC, 2011
[5]
Ramaswamy S, Krishnan J, Forejt B, et al. A high-performance digital-input class-D amplifier with direct battery connection in a 90nm digital CMOS process. Digest of Technical Papers, IEEE International Solid-State Circuits Conference, 2008:436 http://ieeexplore.ieee.org/document/4523244/
[6]
Teplechuk M A, Gribben T, Amadi C. True filterless class-D audio amplifier. IEEE J Solid-State Circuits, 2011, 46(12):2784 doi: 10.1109/JSSC.2011.2162913
[7]
Gaalaas E, Liu B Y, Nishimura N. Integrated stereo delta-sigma class D amplifier. Digest of Technical Papers, IEEE International Solid-State Circuits Conference, 2005:120 http://ieeexplore.ieee.org/document/1493898/
[8]
Goldberg J M, Sandler M B. New high accuracy pulse width modulation based digital-to-analogue convertor/power amplifier. IEE Proceedings Circuits, Devices and Systems, 1994, 141(4):315 doi: 10.1049/ip-cds:19941102
[9]
Nielsen K, Olufsen B, Denmark. A review and comparison of pulse width modulation (PWM) methods for analog and digital input switching power amplifiers. AES E-Library, 1997, 102:4446 http://www.aes.org/e-lib/browse.cfm?elib=7333
[10]
Berkhout M, Dooper L. Class-D audio amplifiers in mobile applications. IEEE Trans Circuits Syst Ⅰ:Regular Papers, 2010, 57(5):992 doi: 10.1109/TCSI.2010.2046200
[11]
Berkhout M. An integrated 200-W class-D audio amplifier. IEEE J Solid-State Circuits, 2003, 38(7):1198 doi: 10.1109/JSSC.2003.813238
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    Received: 26 March 2013 Revised: 09 June 2013 Online: Published: 01 November 2013

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      Shumeng Luo, Dongmei Li. A digital input class-D audio amplifier with sixth-order PWM[J]. Journal of Semiconductors, 2013, 34(11): 115001. doi: 10.1088/1674-4926/34/11/115001 S M Luo, D M Li. A digital input class-D audio amplifier with sixth-order PWM[J]. J. Semicond., 2013, 34(11): 115001. doi: 10.1088/1674-4926/34/11/115001.Export: BibTex EndNote
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      Shumeng Luo, Dongmei Li. A digital input class-D audio amplifier with sixth-order PWM[J]. Journal of Semiconductors, 2013, 34(11): 115001. doi: 10.1088/1674-4926/34/11/115001

      S M Luo, D M Li. A digital input class-D audio amplifier with sixth-order PWM[J]. J. Semicond., 2013, 34(11): 115001. doi: 10.1088/1674-4926/34/11/115001.
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      A digital input class-D audio amplifier with sixth-order PWM

      doi: 10.1088/1674-4926/34/11/115001
      Funds:

      the National Natural Science Foundation of China 61171001

      Project supported by the National High Technology Research and Development Program of China (No. 2012AA012301) and the National Natural Science Foundation of China (No. 61171001)

      the National High Technology Research and Development Program of China 2012AA012301

      More Information
      • Corresponding author: Li Dongmei, ei@tsinghua.edu.cn
      • Received Date: 2013-03-26
      • Revised Date: 2013-06-09
      • Published Date: 2013-11-01

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