Adviser : Hwi-Ming Wang Student : Wei-Guo Zhang Date : 2009/7/14 A Low-Power Low-Voltage 10-bit 100-MSample/s Pipeline A/D Converter Using Capacitance Coupling Techniques Kazutaka Honda, Student Member, IEEE, Masanori Furuta, Member, IEEE, and Shoji Kawahito, Senior Member, IEEE Adviser : Hwi-Ming Wang Student : Wei-Guo Zhang Date : 2009/7/14 1

Outline ABSTRACT INTRODUCTION DESIGN OF KEY BUILDING BLOCKS MEASUREMENT RESULTS CONCLUSION REFERENCES Wei-guo zhang 2009/7/14 2 EE,STUT

Abstract This paper presents a low-power low-voltage 10-bit 100-MSample/s pipeline analog-to-digital converter using capacitance coupling techniques A capacitance coupling sampleand-hold stage achieves high SFDR with 1.0-V supply voltage at a high sampling rate A capacitance coupling folded-cascode amplifier effectively saves the power consumption of the gain stages of the ADC in a 90-nm digital CMOS technology SNDR of 55.3dB ;SFDR of 71.5 dB power consumption is 33mW at 1.0V supply voltage Wei-guo zhang 2009/7/14 3 EE,STUT

Introduction High-performance ADC is one of the key analog building blocks in system-on-a-chip (SoC) visual and telecommunication To exploit advanced sub-100-nm CMOS technology optimized for digital systems, the ADC is desired to be designed with the same devices and supply voltage as those used for the digital system. As device feature size is scaled down, digital circuits benefit greatly from both speed and power dissipation. For analog circuits, however, the decrease of supply voltage consequently causes reduced signal swing and degraded performances in switches and amplifiers Wei-guo zhang 2009/7/14 4 EE,STUT

Introduction Pipeline architectures have been widely employed in applications requiring high speed and high resolution with relatively low power dissipation supply voltage of 1.2 v For lower-voltage operation,the switched opamp (SO) technique is proposed to overcome the switch driving problem caused by an insufficient gate-source voltage This technique tends to slow operation due to slow transients from the opamp being switched on and off. Moreover, to maintain the same signal-to-noise ratio (SNR) with a lower supply voltage, the thermal noise in the circuit must also be proportionately reduced .This means that the sampling capacitance must be increased to reduce KT/C noise. Wei-guo zhang 2009/7/14 5 EE,STUT

Introduction This paper proposes two capacitance coupling techniques for low-power low-supply-voltage pipeline ADCs in sub-100-nm CMOS technology A prototype 10-bit 100-MSample/s pipeline ADC employing these techniques achieves low-power and low-distortion characteristics in 1.0-V 90-nm CMOS Wei-guo zhang 2009/7/14 6 EE,STUT

DESIGN OF KEY BUILDING BLOCKS Wei-guo zhang 2009/7/14 7 EE,STUT

DESIGN OF KEY BUILDING BLOCKS In low-voltage operation, one of the most difficult problems in a S/H stage is the high on-resistance of sampling switches due to the reduced gate-source voltage The switched opamp formed in a charge transfer S/H architecture has disadvantages in terms of gain bandwidth and noise The flip-around architecture.This technique requires Additional time for starting up from the off-state of the opamp limits the sampling rate Wei-guo zhang 2009/7/14 8 EE,STUT

DESIGN OF KEY BUILDING BLOCKS The schematic of the proposed S/H circuit with a capacitance coupling technique. Wei-guo zhang 2009/7/14 9 EE,STUT

DESIGN OF KEY BUILDING BLOCKS This configuration achieves high sampling rate with low distortion, because of the low on-resistance of switches and no start-up time of the amplifier In our design, 　is 0.82 with Csh=2pF Cc=1pF Cin=0.15pF Wei-guo zhang 2009/7/14 10 EE,STUT

DESIGN OF KEY BUILDING BLOCKS This amplifier utilizes a dynamical-bias gain boosting technique to have sufficient signal swing and allows the output swing of 0.8 vpp in differential signal under a 1.0-V power supply Wei-guo zhang 2009/7/14 11 EE,STUT

DESIGN OF KEY BUILDING BLOCKS The conventional S/H stage has a relatively large harmonic distortion SFDR=61.2dB Using the capacitance coupling technique SFDR=84.8dB It indicates that the CCSH architecture can achieve low-distortion sampling with 1.0-V supply voltage Wei-guo zhang 2009/7/14 12 EE,STUT

DESIGN OF KEY BUILDING BLOCKS A class-AB capacitance coupling folded-cascode (CCFC) amplifier. The simulated DC open-loop gain is about 76 dB and the gain bandwidth (GBW) of the first stage’s amplifier is 1.5 GHz Wei-guo zhang 2009/7/14 13 EE,STUT

DESIGN OF KEY BUILDING BLOCKS Vod is the overdrive voltage of the input transistor and Io is the unit bias current The settling time can be reduced to 40% without increasing the static power Wei-guo zhang 2009/7/14 14 EE,STUT

DESIGN OF KEY BUILDING BLOCKS Including the bias circuits, and clock generator, the total static power dissipation of the ADC is estimated to be 26.6 mW with 1.0-V supply voltage Wei-guo zhang 2009/7/14 15 EE,STUT

MEASUREMENT RESULTS Two types of prototype pipeline ADCs were fabricated in a 90-nm, six-metal one-poly (6M1P) digital CMOS technology The total power consumption of the first prototype is only 30 mW consisting of 28.5 mW for analog and 1.5 mW for digital at 100 MSample/s with a 1.0-V supply excluding the digital output drivers The second prototype consumes 33 mW, which means that the on-chip error correction logic consumes 3 mW at 100 MHz Wei-guo zhang 2009/7/14 16 EE,STUT

MEASUREMENT RESULTS Differential Non-Linearity and Integral Non-Linearity Wei-guo zhang 2009/7/14 17 EE,STUT

MEASUREMENT RESULTS The FFT spectra for 12 MHz input sampled at 100 MSample/s The SNDR and SFDR are improved by 11 and 26 dB ENOB=8.9bit Without calibration SNDR and SFDR by 44 and 45.5 dB Wei-guo zhang 2009/7/14 18 EE,STUT

MEASUREMENT RESULTS SNDR and SFDR of 2nd by 53.1and 68.4dBat the Nyquist frequency of 50 MHz The SNDR keeps above 50 dB up to 200 MHz while the SFDR degrades for over Nyquist input frequency SNDR and SFDR of both prototypes as a function of conversion rate at an input frequency of 10 MHz Wei-guo zhang 2009/7/14 19 EE,STUT

MEASUREMENT RESULTS The SNDR and SFDR of the second prototype atVDD=0.9V are 54.1 and 69.8 dB The SFDR remain above 64 dB down to 0.8 V at 100MS/s. SNDR and SFDR=55.3 and 71.5 dB Wei-guo zhang 2009/7/14 20 EE,STUT

MEASUREMENT RESULTS FOM1 of ADC given by FOM2 which reflect the difficulties for dynamic range limited designs, defined by Wei-guo zhang 2009/7/14 21 EE,STUT

Conclusion This paper describes capacitance coupling techniques to reduce the power dissipation of a 10-bit 100-MSample/s pipeline ADC while keeping low distortion in 90-nm CMOS process The prototype ADC at 100 MSample/s achieves 8.9 ENOB and SFDR of 71.5 dB at 1.0-V supply voltage and dissipates only 33 mW This ADC is useful for wideband visual and communication systems. Wei-guo zhang 2009/7/14 22 EE,STUT

REFERENCES [1] International Technology Roadmap for Semiconductors, Semiconductor Industry Association, 2005. [2] B. Hernes, A. Briskemyr, T. N. Andersen, F. Telstø, T. E. Bonnerud,andØ.Moldsvor, “A1.2V220 MS/s 10 bit pipeline ADCimplemented in 0.13 m digital CMOS,” in IEEE ISSCC 2004 Dig. Tech. Papers,Feb. 2004, pp. 256–257. [3] R. Wang, K. Martin, D. Johns, and G. Burra, “A 3.3 mW 12 MS/s 10 bit pipelined ADC in 90 nm digital CMOS,” in IEEE ISSCC 2005 Dig.Tech. Papers, Feb. 2005, pp. 278–279. [4] M.Waltari and K. A. I. Halonen, “1-V 9-bit pipelined switched-opamp ADC,” IEEE J. Solid-State Circuits, vol. 36, no. 1, pp. 129–134, Jan.2001. [5] A. M. Abo and P. R. Gray, “A 1.5-V, 10-bit, 14.3-MS/s CMOS pipeline analog-to-digital converter,” IEEE J. Solid-State Circuits, vol. 34, no.5, pp. 599–606, May 1999. [6] K. Honda, M. Furuta, and S. Kawahito, “A 1 V 30 mW 10 bit 100 MSample/s pipeline A/D converter using capacitance coupling techniques,”in Symp. VLSI Circuits 2006 Dig. Tech. Papers, Jun. 2006, pp.276–277. [7] M. Furuta, S. Kawahito, and D. Miyazaki, “A digital calibration technique for capacitor mismatch for pipelined analog-to-digital converters,” IEICE Trans. Electron., vol. E85-C, no. 8, pp. 1562–1568, Aug. 2002. [8] D. Miyazaki, M. Furuta, and S. Kawahito, “A 75 mW 10 bit 120 MSample/s parallel pipeline ADC pipeline A/D,” in Proc. Eur. Solid-State Circuits Conf. (ESSCIRC 2003), Sep. 2003, pp. 719–722. Wei-guo zhang 2009/7/14 23 EE,STUT