Journal of the Institute of Electronics and Information Engineers (전자공학회논문지)

The Institute of Electronics and Information Engineers (대한전자공학회)
권호 표지
DOI QR코드

DOI QR Code

Design of a 10-bit SAR ADC with Enhancement of Linearity On C-DAC Array

C-DAC Array내 선형성을 향상시킨 10비트 CMOS SAR ADC 설계

  • Received : 2016.06.03
  • Accepted : 2017.01.19
  • Published : 2017.02.25
Download PDF
⟨ Previous Next ⟩

Abstract

In this paper, CMOS SAR A/D converter 1.8V supply for the design of an A/D converter having an middle speed for the biological signal processing was designed. This paper proposes design of a 10-bit SAR Analog to Digital Converter improving linearity driven by MSB node of C-DAC array divided into 4 equal parts. It enhances linearity property, by retaining the analog input signal charging time at MSB node. Because MSB node samples analog input, it enhances resolution through getting initial input signal precisely. By using split capacitor on C-DAC array, it reduced chip size and power dissipation. The Proposed SAR A/D Converter is fabricated in 0.18um CMOS and measured 7.5 bits of ENOB at sampling frequency 4MS/s and power supply of 1.8V. It occupies a core area of $850{\times}650um^2$ and consumes 123.105uW. Therefore it results in 170.016fJ/step of FOM(Figure of Merit).

본 논문에서는 생체 신호 처리를 위한 중간 속도를 갖는 A/D 변환기 설계를 위하여 1.8V 전원의 CMOS SAR(Successive Approximation Register) A/D 변환기를 설계하였다. 본 논문에서 C-DAC Array의 MSB단을 4분할하여 선형성을 향상시킨 10비트 SAR A/D 변환기 설계를 제안한다. 아날로그 입력이 인가되는 MSB 단의 전하가 충전되는 시간을 확보하여 선형성을 높였다. MSB단이 아날로그 입력을 샘플링하는 블록이기 때문에 초기 값을 보다 정교하게 받아들이는 원리를 통해 선형성을 확보하였다. C-DAC에서 Split 커패시터를 사용하여 면적을 최소화하고, 전력을 감소시켰다. 제안된 SAR A/D 변환기는 0.18um CMOS 공정을 이용하여 설계하였고, 공급 전압 1.8V에서 4MS/s의 변환속도를 가지며, 7.5비트의 ENOB(Effective Number of Bit)이 측정되었다. $850{\times}650um^2$의 면적, 총 전력소모는 123.105uW이고, 170.016fJ/step의 FOM(Figure of Merit)을 확인할 수 있다.

Keywords

References

  1. Tsung-Che Lu, Lan-Da Van, Chi-Sheng Lin, Chun-Ming Huang, "A 0.5V 1KS/s 2.5nW 8.52-ENOB 6.8fJ/Conversion-Step SAR ADC for Biomedical Applications," 2011 IEEE CICC, pp. 1-4, San Jose, CA, Sept 2011.
  2. Sang-Hyun Cho, Chang-Kyo Lee, Jong-Kee Kwon, Seung-Tak Ryu, "A 550-uW 10-b 40-MS/s SAR ADC With Multistep Addition-Only Digital Error Correction," IEEE JSSC, Vol. 46, no. 8, pp. 1881-1892, Aug 2011.
  3. Chun-Cheng Liu, Soon-Jyh Chang, Guan-Ying Huang, Yin-Zu Lin, "A 0.92mW 10-bit 50-MS/s SAR ADC in $0.13{\mu}m$ CMOS Process," 2009 Symposium on VLSI Circuits, pp. 236-237, Kyoto, Japan, Jun 2009.
  4. Yung-Hui Chung, Meng-Hsuan Wu, and Hung-Sung Li "A 12-bit 8.47-fJ/Conversion-Step Capacitor-Swapping SAR ADC in 110-nm CMOS," IEEE Transactions on and systems, Vol. 62, NO.1, Jan 2015.
  5. Yan Zhu, Chi-Hang Chan, U-Fat Chio, Sai-Weng Sin, Seng-Pan U, Rui Paulo Martins and Franco Maloberti, "Split-SAR ADCs: Improved Linearity With Power and Speed Optimization," IEEE Transactions on VLSI Systems, Vol. 22, NO. 2, Feb 2014.
  6. Howard Tang, Zhuo Chao Sun, Kin Wai Roy Chew, Liter Siek "A 1.33 uW 8.02-ENOB 100 kS/s Successive Approximation ADC With Supply Reduction Technique for Implantable Retinal Prosthesis," IEEE J. Solid-State Circuits, Vol. 50, NO.4, April 2015.
  7. Jin-Yi Lin, Chih-Cheng Hsieh, "A 0.3 V 10-bit 1.17f SAR ADC With Merge and Split Switching in 90nm CMOS," IEEE Transactions on and systems, Vol. 62, NO.1, Jan 2015.
  8. Guan-Ying Huang, Soon-Jyh Chang, Chun-Cheng Liu, Ying-Zu Lin "A $1-{\mu}m$ 10-bit 200-kS/s SAR ADC With a Bypass Window for Biomedical Applications," IEEE J. Solid-State Circuits, Vol. 47, pp. 2783-2795, Nov 2012. https://doi.org/10.1109/JSSC.2012.2217635
  9. Y Chen, X. Zhu, T. Hirotaka. "Split capacitor DAC mismatch calibration in successive approximation ADC," J. IEEE CICC, pp. 279-282, San jose, CA, Sept 2009.
  10. Binhee Kim, Long Yan, Jerald Yoo, Hoi-Jun Yoo, "A 40fJ/c-s 1 V 10 bit SAR ADC with Dual Sampling Capacitive DAC Topology," JSTS, pp. 23-32, Vol. 11, No. 1, Mar 2011. https://doi.org/10.5573/JSTS.2011.11.1.023
  11. Shin-Il Lim, Jin Woo Kim, Kwang-Sub Yoon, Sangmin Lee, "A 12-b Asynchronous SAR Type ADC for Bio Signal Detection," JSTS, pp. 108-113, Vol. 13, No. 2, Apr 2013. https://doi.org/10.5573/JSTS.2013.13.2.108