Ultrafast switching speed, low power, natural quantization of magnetic flux, quantum accuracy, and low noise of cryogenic superconductor circuits enable fast and accurate data conversion between the analog and digital domains. Based on rapid single-flux quantum (RSFQ) logic, these integrated circuits are capable of achieving performance levels unattainable by any other technology. Two major classes of superconductor analog-to-digital converters (ADCs) are being developed - Nyquist sampling and oversampling converters. Complete systems with digital sampling at rates of /spl sim/20 GHz and above have been demonstrated using low-temperature superconductor device technology. Some ADC components have also been implemented using high-temperature superconductors. Superconductor ADCs have unique applications in true digital-RF communications, broadband instrumentation, and digital sensor readout. Their designs, test results, and future development trends are reviewed.

/pdf/superconductor-analog-to-digital-converters-5db83fuox2.pdf

Superconductor analog-to-digital converters

We present a 6-bit 1.2-GS/s flash-ADC with wide analog bandwidth and low power, realized in a standard digital 0.13 /spl mu/m CMOS copper technology. Employing capacitive interpolation gives various advantages when designing for low power: no need for a reference resistor ladder, implicit sample-and-hold operation, no edge effects in the interpolation network (as compared to resistive interpolation), and a very low input capacitance of only 400 fF, which leads to an easily drivable analog converter interface. Operating at 1.2 GS/s the ADC achieves an effective resolution bandwidth (ERBW) of 700 MHz, while consuming 160 mW of power. At 600 MS/s we achieve an ERBW of 600 MHz with only 90 mW power consumption, both from a 1.5 V supply. This corresponds to outstanding figure-of-merit numbers (FoM) of 2.2 and 1.5 pJ/convstep, respectively. The module area is 0.12 mm/sup 2/.

A 6-bit 1.2-GS/s low-power flash-ADC in 0.13-/spl mu/m digital CMOS

A quadrature cascaded modulator with continuous-time loop filters is presented for a digital multi-stream FM radio receiver. The ADC achieves a dynamic range of 77 dB and 20 MHz bandwidth centered on an intermediate frequency of 10.5 MHz and is sampling at 340 MHz. The cascaded modulator comprises programmable analog second-order quadrature filters and a digital quadrature noise cancellation filter. The 0.5 chip in 90 nm CMOS consumes 56 mW from a 1.2 V supply.

A 56 mW Continuous-Time Quadrature Cascaded $\Sigma\Delta$ Modulator With 77 dB DR in a Near Zero-IF 20 MHz Band

Embodiments include a decision feedback equalizer (DFE) circuit, including at least one reorder block configured to reorder a set of current sliced bit values based on one or more previous sliced bit values, and a selector configured to select one of the reordered current sliced bit values as a DFE output based on a group of non-adjacent DFE outputs.

Equalizer with reorder

A microcontroller with a mixed analog/digital architecture including multiple digital programmable blocks and multiple analog programmable blocks in a communication array having a programmable interconnect structure. The single chip design is implemented by integration of programmable digital and analog circuit blocks that are able to communicate with each other. Robust analog and digital blocks that are flash memory programmable can be utilized to realize complex design applications that otherwise would require multiple chips and/or separate applications. The programmable chip architecture includes a novel array having programmable digital blocks that can communicate with programmable analog blocks using a programmable interconnect structure. The programmable analog array contains a complement of Continuous Time (CT) blocks and a complement of Switched Capacitor (SC) blocks that can communicate together. The analog blocks consist of multi-function circuits programmable for one or more different analog functions, and fixed function circuits programmable for a fixed function with variable parameters. The digital blocks include standard multi-function circuits and enhanced circuits having functions not included in the standard digital circuits. The programmable array is programmed by flash memory and programming allows dynamic reconfiguration. That is, “on-the-fly” reconfiguration of the programmable blocks is allowed. The programmable analog array with both Continuous Time analog blocks and Switched Capacitor analog blocks are offered on a single chip along with programmable digital blocks. The programmable interconnect structure provides for communication of input/output data between all analog and digital blocks.

Programmable microcontroller architecture(mixed analog/digital)

Provided is a circuit to perform single-ended to differential conversion while providing common-mode voltage control. The circuit includes a converter to convert a single-ended signal to a differential signal and a stabilizing circuit adapted to receive the differential signal. The stabilizing circuit includes a sensor configured to sense a common-mode voltage level of the differential signal and a comparator having an output port coupled to the converter. The comparator is configured to compare the differential signal common-mode voltage level with a reference signal common-mode voltage level and produce an adjusting signal based upon the comparison. The adjusting signal is applied to the converter via the output port and is operative to adjust a subsequent common-mode voltage level of the differential signal.

Single-ended-to-differential converter with common-mode voltage control

An N-bit analog to digital converter includes a reference ladder, a track-and-hold amplifier connected to an input voltage, a coarse ADC amplifier connected to a coarse capacitor at its input and having a coarse ADC reset switch controlled by a first clock phase of a two-phase clock, a fine ADC amplifier connected to a fine capacitor at its input and having a fine ADC reset switch controlled by a second clock phase of the two-phase clock, a switch matrix that selects a voltage subrange from the reference ladder for use by the fine ADC amplifier based on an output of the coarse ADC amplifier, and wherein the coarse capacitor is charged to a coarse reference ladder voltage during the first clock phase and connected to the T/H output during the second clock phase, wherein the fine capacitor is connected to a voltage subrange during the first clock phase and to the T/H output during the second clock phase, and an encoder that converts outputs of the coarse and fine ADC amplifiers to an N-bit output.

Subranging analog to digital converter with multi-phase clock timing

This paper presents an 8-b two-step subranging analog-to-digital (ADC) using interpolation, averaging, offset compensation, and pipelining techniques to accomplish an effective number of bits of 7.6 b at 125 MSample/s. The 0.13-/spl mu/m CMOS ADC occupies 0.09 mm/sup 2/ and consumes 21 mW.

A 21-mW 8-b 125-MSample/s ADC in 0.09-mm/sup 2/ 0.13-/spl mu/m CMOS

An All-Digital PLL (ADPLL) in 28 nm CMOS is designed to generate low noise clocks for high-speed ADCs. A high-resolution (<; 1 ps), short-span (6 ps) Time-to-Digital Converter (TDC) is implemented to improve the phase noise with little cost of power and area. This ADPLL has <; 230 fs RMS jitter at 50 MHz reference frequency, with 8.5 mW power from 1.8V supply and an area of 0.07 mm2.

An 8.5 mW, 0.07 mm 2 ADPLL in 28 nm CMOS with sub-ps resolution TDC and < 230 fs RMS jitter

A differential comparator with improved bit-error rate performance operating with a low supply voltage. The differential comparator includes a first pair of transistors receiving a differential input. A second pair of transistors is coupled to the first pair of transistors. A pair of resistive elements is connected between the first pair and second pair of transistors so as to increase bias currents shared by the first and second pairs of transistors. The increased bias currents reduce a time required by the differential comparator to transition from a meta-stable state to a stable state, thereby improving a bit-error rate of the differential comparator. The resistive elements can use linear resistors or transmission gates. Gates of either the first or second pair of transistors can provide an output.

Marcel Lugthart

Papers

Single-ended-to-differential converter with common-mode voltage control

Subranging analog to digital converter with multi-phase clock timing

A 21-mW 8-b 125-MSample/s ADC in 0.09-mm/sup 2/ 0.13-/spl mu/m CMOS

An 8.5 mW, 0.07 mm 2 ADPLL in 28 nm CMOS with sub-ps resolution TDC and < 230 fs RMS jitter

High-speed comparator