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 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

Although charge-redistribution successive approximation (SAR) ADCs are highly efficient, comparator noise and other effects limit the most efficient operation to below 10-b ENOB. This work introduces an oversampling, noise-shaping SAR ADC architecture that achieves 10-b ENOB with an 8-b SAR DAC array. A noise-shaping scheme shapes both comparator noise and quantization noise, thereby decoupling comparator noise from ADC performance. The loop filter is comprised of a cascade of a two-tap charge-domain FIR filter and an integrator to achieve good noise shaping even with a low-quality integrator. The prototype ADC is fabricated in 65-nm CMOS and occupies a core area of 0.03 mm2. Operating at 90 MS/s, it consumes 806 μW from a 1.2-V supply.

A 90-MS/s 11-MHz-Bandwidth 62-dB SNDR Noise-Shaping SAR ADC

The IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences announces a forthcoming Special Section on Networked Control Systems: Theories & Applications to be published in May 2013. In many applications, such as factory automation and smart grid, Networked Control System (NCS) plays an important role, in which the state of environment is monitored and the target is controlled both via the network. Based on conventional control and communication theories, a new unified theory on NCS is needed to realize reliable, robust, delay tolerant, and scalable communication networks for NCS. Under these considerations, Special Section on Networked Control Systems: Theories & Applications is planned to accelerate R&D activities in this area by collecting and publishing the results on up-to-date researches and experimental studies related to NCS.

IEICE transactions on fundamentals of electronics, communications and computer sciences

This paper presents a 60-GHz direct-conversion RF front-end and baseband transceiver including analog and digital circuitry for PHY functions. The 65-nm CMOS front-end consumes 319 and 223 mW in transmitting and receiving mode, respectively. It is capable of more than 7-Gb/s 16QAM wireless communication for every channel of the 60-GHz standards, which can be extended up to 10 Gb/s. The 40-nm CMOS baseband including analog, digital, and I/O consumes 196 and 427 mW for 16QAM in transmitting and receiving modes, respectively. In the analog baseband, a 5-b 2304-MS/s ADC consumes 12 mW, and a 6-b 3456-MS/s DAC consumes 11 mW. In the digital baseband integrating all PHY functions, a (1440, 1344) LDPC decoder consumes 74 mW with the low energy efficiency of 11.8 pJ/b. The entire system including both RF and BB using a 6-dBi antenna built in the organic package can transmit 3.1 Gb/s over 1.8 m in QPSK and 6.3 Gb/s over 0.05 m in 16QAM.

Full Four-Channel 6.3-Gb/s 60-GHz CMOS Transceiver With Low-Power Analog and Digital Baseband Circuitry

This paper presents a 100 kS/s, 1.3 μW, 9.3 ENOB successive approximation ADC with a time-domain comparator. The proposed time-domain comparator utilizes a differential multi-stage VCDL, resulting in a highly digital operation eliminating static power consumption. The effects of gain, noise, and offset are also investigated by detailed analysis which proves the feature of reducing the input-referred noise and offset by simply increasing the number of delay stages. For verification, the proposed ADC is fabricated in a 0.18 μm CMOS. With a single supply voltage of 0.6 V, the ADC consumes 1.3 μW at the maximum sampling rate of 100 kS/s. The measured ENOB is 9.3 b showing a figure of merit of 21 f J/conversion-step.

A 21 fJ/Conversion-Step 100 kS/s 10-bit ADC With a Low-Noise Time-Domain Comparator for Low-Power Sensor Interface

This paper presents a low offset voltage, low noise dynamic latched comparator using a self-calibrating technique. The new calibration technique does not require any amplifiers for the offset voltage cancellation and quiescent current. It achieves low offset voltage of 1.69 mV at 1 sigma in low power consumption, while 13.7 mV is measured without calibration. Furthermore the proposed comparator requires only one phase clock while conventionally two phase clocks were required leading to relaxed clock. Moreover, a low input noise of 0.6 mV at 1 sigma, three times lower than the conventional one, is obtained. Prototype comparators are realized in 90 nm 10M1P CMOS technology. Experimental and simulated results show that the comparator achieves 1.69 mV offset at 250 MHz operating, while dissipating 40 muW/GHz ( 20 fJ/conv. ) from a 1.0 V supply.

A low-noise self-calibrating dynamic comparator for high-speed ADCs

This paper presents a 0.55 V, 7 bit, 160 MS/s pipeline ADC using dynamic amplifiers. In this ADC, high-speed open-loop dynamic amplifiers with a common-mode detection technique are used as residue amplifiers to increase the ADC's speed, to enhance the robustness against supply voltage scaling, and to realize clock-scalable power consumption. To mitigate the absolute gain constraint of the residue amplifiers in a pipeline ADC, the interpolated pipeline architecture is employed to shift the gain requirement from absolute to relative accuracy. To show the new requirements of the residue amplifiers, the effects of gain mismatch and nonlinearity of the dynamic amplifiers are analyzed. The 7 bit prototype ADC fabricated in 90 nm CMOS demonstrates an ENOB of 6.0 bits at a conversion rate of 160 MS/s with an input close to the Nyquist frequency. At this conversion rate, it consumes 2.43 mW from a 0.55 V supply. The resulting FoM of the ADC is 240 fJ/conversion-step.

An Ultra-Low-Voltage 160 MS/s 7 Bit Interpolated Pipeline ADC Using Dynamic Amplifiers

An open-loop interpolated pipeline ADC is proposed. Weight controlled capacitor arrays are introduced to realize an interpolation and a pipelined operation with open-loop amplifiers. The 10-bit ADC fabricated in 90 nm CMOS demonstrates ENOB of 8.5b over 80 MHz bandwidth (BW) and a conversion rate of 320 MS/s without linearity compensation and consumes 40 mW. The FoMs are 780 fJ/c.-s. defined by the 80 MHz BW and 390 fJ/c.-s. defined by the 320 MSps conversion rate with a BW of 80 MHz.

/pdf/a-10b-320-ms-s-40-mw-open-loop-interpolated-pipeline-adc-24xhekhx3e.pdf

A 10b 320 MS/s 40 mW open-loop interpolated pipeline ADC

This paper analyzes a pseudo-differential dynamic comparator with a dynamic pre-amplifier. The transient gain of a dynamic pre-amplifier is derived and applied to equations of the thermal noise and the regeneration time of a comparator. This analysis enhances understanding of the roles of transistor's parameters in pre-amplifier's gain. Based on the calculated gain, two calibration methods are also analyzed. One is calibration of a load capacitance and the other is calibration of a bypass current. The analysis helps designers' estimation for the accuracy of calibration, dead-zone of a comparator with a calibration circuit, and the influence of PVT variation. The analyzed comparator uses 90-nm CMOS technology as an example and each estimation is compared with simulation results.

/pdf/an-analysis-on-a-dynamic-amplifier-and-calibration-methods-3joaufs8sf.pdf

An Analysis on a Dynamic Amplifier and Calibration Methods for a Pseudo-Differential Dynamic Comparator

This paper analyzes a pseudo-differential dynamic comparator with a dynamic pre-amplifier. The transient gain of a dynamic pre-amplifier is derived. This analysis enhances understanding of the roles of a transistor's parameters in a pre-amplifier's gain. Based on the calculated gain, a load capacitance calibration method is analyzed. The analysis helps designers' estimation for the accuracy of the calibration and the influence of PVT variation. The analyzed comparator uses 90-nm CMOS technology as an example and each estimation is compared with the simulation results.

/pdf/an-analysis-on-a-pseudo-differential-dynamic-comparator-with-4tsw0xabvs.pdf

Daehwa Paik

Papers

A low-noise self-calibrating dynamic comparator for high-speed ADCs

An Ultra-Low-Voltage 160 MS/s 7 Bit Interpolated Pipeline ADC Using Dynamic Amplifiers

A 10b 320 MS/s 40 mW open-loop interpolated pipeline ADC

An Analysis on a Dynamic Amplifier and Calibration Methods for a Pseudo-Differential Dynamic Comparator

An analysis on a pseudo-differential dynamic comparator with load capacitance calibration