Seng-Pan U

Bio: Seng-Pan U is an academic researcher from University of Macau. The author has contributed to research in topics: Successive approximation ADC & Effective number of bits. The author has an hindex of 12, co-authored 23 publications receiving 385 citations. Previous affiliations of Seng-Pan U include Synopsys.

A 3.8mW 8b 1GS/s 2b/cycle interleaving SAR ADC with compact DAC structure

Abstract: An 8b 1GS/s ADC is presented that interleaves two 2b/cycle SARs. To enhance speed and save power, the prototype utilizes segmentation switching and custom-designed DAC array with high density in a low parasitic layout structure. It operates at 1GS/s from 1V supply without interleaving calibration and consumes 3.8mW of power, exhibiting a FoM of 24fJ/conversion step. The ADC occupies an active area of 0.013mm2 in 65nm CMOS including on-chip offset calibration.

Split-SAR ADCs: Improved Linearity With Power and Speed Optimization

Abstract: This paper presents the linearity analysis of a successive approximation registers (SAR) analog-to-digital converters (ADC) with split DAC structure based on two switching methods: conventional charge-redistribution and Vcm-based switching. The static linearity performance, namely the integral nonlinearity and differential nonlinearity, as well as the parasitic effects of the split DAC, are analyzed hereunder. In addition, a code-randomized calibration technique is proposed to correct the conversion nonlinearity in the conventional SAR ADC, which is verified by behavioral simulations, as well as measured results. Performances of both switching methods are demonstrated in 90 nm CMOS. Measurement results of power, speed, and linearity clearly show the benefits of using Vcm-based switching.

Design and Experimental Verification of a Power Effective Flash-SAR Subranging ADC

Abstract: This brief presents the architectural concept of an optimal subranging ADC, obtained with the cascade of a Flash and a SAR, which is also explored through its practical design and experimental confirmation. The solution doubles the optimal speed of operation of the SAR ADCs at the relative low power cost of a low-resolution Flash. The digital correction method and a capacitor-based DAC ensure nondemanding requirements for the Flash. The effectiveness of the architecture is verified in a 90-nm CMOS chip whose active core area is 0.64 mm2. The ADC obtains a peak SNDR of 51.8 dB and SFDR of 63.4 dB at 90 MS/s consuming 13.5 mW from a 0.9-V supply. Measured DNL and INL are 0.87 LSB and 1.55 LSB, respectively.

A 2.3 mW 10-bit 170 MS/s Two-Step Binary-Search Assisted Time-Interleaved SAR ADC

Abstract: This paper presents the architecture of a 10b 170 MS/s two-step binary-search assisted time-interleaved SAR ADC. The front-end stage of this ADC is built with a 5b binary-search ADC, which is shared by two time-interleaved 6b SAR ADCs in the second-stage. The design does not use any static component such as op-amp or preamplifier that causes large dissipation of static power. DAC settling speed and power are also relaxed thanks to this architecture. Besides, the process insensitive asynchronous logic further reduces the delay of SA loop rather than using worst case delay cells to compensate the process variation problem. The ADC was fabricated in 65 nm CMOS and achieves 54.6 dB SNDR at 170 MS/s with only 2.3 mW of power consumption, leading to a FoM of 30.8 fJ/conversion-step.

A 34fJ 10b 500 MS/s partial-interleaving pipelined SAR ADC

Abstract: A 10b 500MS/s ADC is presented that shares a full-speed SAR at front-end and interleaves the pipelined residue amplification with shared opamp and 2nd-stage SAR ADCs, which achieves high speed, low power and compact area. The prototype ADC in 65nm CMOS achieves a mean SNDR of 55.4dB with 8.2mW power dissipation at 1.2V. The active die area including the offset calibrations is 0.046mm2.

A 3.1 mW 8b 1.2 GS/s Single-Channel Asynchronous SAR ADC With Alternate Comparators for Enhanced Speed in 32 nm Digital SOI CMOS

Abstract: An 8b 1.2 GS/s single-channel Successive Approximation Register (SAR) ADC is implemented in 32 nm CMOS, achieving 39.3 dB SNDR and a Figure-of-Merit (FoM) of 34 fJ per conversion step. High-speed operation is achieved by converting each sample with two alternate comparators clocked asynchronously and a redundant capacitive DAC with constant common mode to improve the accuracy of the comparator. A low-power, clocked capacitive reference buffer is used, and fractional reference voltages are provided to reduce the number of unit capacitors in the capacitive DAC (CDAC). The ADC stacks the CDAC with the reference capacitor to reduce the area and enhance the settling speed. Background calibration of comparator offset is implemented. The ADC consumes 3.1 mW from a 1 V supply and occupies 0.0015 mm2.

A 550- $\mu\hbox{W}$ 10-b 40-MS/s SAR ADC With Multistep Addition-Only Digital Error Correction

Abstract: A speed-enhanced 10-b asynchronous SAR ADC with multistep addition-only digital error correction (ADEC) is presented with a straightforward DAC switching algorithm. The capacitor DAC is virtually divided into three sub-DACs for ADEC with negligible hardware overhead. The redundant decision cycles between stages reconfigure the capacitor connection of the DAC. These redundancies guarantee 10-b linearity under 4-b-accurate DAC settling in the MSB decision and the optimally designed ADC enhances the conversion speed by 37%. A prototype ADC was implemented in a CMOS 0.13-μm technology. The chip consumes 550 μW and achieves a 50.6-dB SNDR at 40 MS/s under a 1.2-V supply. The figure-of-merit (FOM) is 50 fJ/conversion-step.

A 12-Bit 10 MS/s SAR ADC With High Linearity and Energy-Efficient Switching

Abstract: A 12-bit 10 MS/s SAR ADC with enhanced linearity and energy efficiency is presented in this paper. A novel switching scheme (COSS) is proposed to reduce the power consumption and the matching requirement for capacitors in SAR ADCs. The switching energy (including switching energy and reset energy), total capacitance and static performance (INL & DNL) of the proposed scheme are reduced by 98.08%, 75%, and 75%, respectively, compared with the conventional architecture. Based on analysis of the non-linear errors caused by comparator input parasitic capacitance, an improved comparator with push-pull pre-amplifier and output offset storage (OOS) strategy is proposed to diminish non-linearity in the input parasitic capacitance. The offset cancellation signal for the comparator can be generated by asynchronous timing automatically, without any extra clock. Additionally, an SFDR enhancement bootstrap switch is proposed to eliminate the distortion induced by parasitic capacitance and threshold voltage that results in insufficient precision for medium-speed 12-bit ADCs. The proposed ADC was fabricated in a 0.18 $\mu\text{m}$ 1P6M CMOS process, and the measured results show that the ADC achieves an SNDR of 66.9 dB and an SFDR of 75.8 dB with a 10 MS/s sampling rate and consumes 0.82 mW, resulting in a figure of merit (FOM) of 44.2 fJ/conversion-step. The peak DNL error is +0.36/−0.33 LSB, and the peak INL error is +0.55 LSB/−0.6 LSB. The ADC core occupies an active area of only $630\ \mu\text{m}\! \times\! 570\ \mu\text{m}^{2}$ .

A 10 bit 320 MS/s Low-Cost SAR ADC for IEEE 802.11ac Applications in 20 nm CMOS

Abstract: This paper presents a low-cost successive approximation register (SAR) analog-to-digital converter (ADC) for IEEE 802.11 ac applications. In this paper, a binary-scaled recombination capacitor weighting method is disclosed. The digital sub-blocks in this ADC are composed of standard library logic cells. The prototype is fabricated in a 1P8M 20 nm CMOS technology. At 0.9 V supply and 160 MS/s, the ADC consumes 0.68 mW. It achieves an SNDR of 57.7 dB and 57.13 dB at low and Nyquist input frequency, respectively, resulting in figures of merit (FoMs) of 6.8 and 7.3 fJ/conversion-step, respectively. At 1 V supply and 320 MS/s, the ADC consumes 1.52 mW. It achieves an SNDR of 57.1 dB and 50.89 dB at low and Nyquist input frequency, respectively, resulting in FoMs of 8.1 and 16.5 fJ/conversion-step, respectively. The ADC core only occupies an active area of $33~\mu{\hbox {m}}\times 35\mu{\hbox {m}}$ .

ΣΔ Data Converters

Abstract: First written in 2003 for a book that was never published. Last updated on January 29, 2011. You can find the most recent version at www.designers-guide.org. Contact the author via email at monte.mar@comcast.net. Permission to make copies, either paper or electronic, of this work for personal or classroom use is granted without fee provided that the copies are not made or distributed for profit or commercial advantage and that the copies are complete and unmodified. To distribute otherwise, to publish, to post on servers, or to distribute to lists, requires prior written permission.