Analog Devices Global

Analog Devices Global Unlimited Company

Analog Devices Technology

Analog Devices International Unlimited Company

Trevor Clifford Caldwell

Hajime Shibata

Zhao Li

David Nelson Alldred

Richard E Schreier

Yunzhi Dong

Victor Kozlov

Wenhua William Yang

Jialin Zhao

Prawal Man Shrestha

Christopher Mayer

Kevin Glenn Gard

Siddharth Devarajan

Shipra Bhal

Brian Holford

Ali Sheikholeslami

David J McLaurin

Donald W Paterson

David J Mclaurin

Corey Petersen

Jose Barreiro Silva

David Alldred

A continuous-time sampler has series-connected delay lines with intermediate output taps between the delay lines. Signal from an output tap can be buffered by an optional voltage buffer for performance. A corresponding controlled switch is provided with each output tap to connect the output tap to an output of the continuous-time sampler. The delay lines store a continuous-time input signal waveform within the propagation delays. Controlling the switches corresponding to the output taps with pulses that match the propagation delays can yield a same input signal value at the output. The continuous-time sampler effectively 'holds' or provides the input signal value at the output for further processing without requiring switched-capacitor circuits that sample the input signal value onto some capacitor. In some cases, the continuous-time sampler can be a recursively-connected delay line. The continuous-time sampler can be used as the front end sampler in a variety of analog-to-digital converters.

Continuous-time sampler circuits

A linear continuous-time (CT) delaying summation block is one of the key building blocks for CT multi-stage analog-to-digital converters (ADCs) such as CT pipeline ADCs and CT multi-stage delta-sigma (MASH) ADCs. The CT summation block is typically used on a stage of a CT multi-stage ADC to subtract a digital-to-analog converter (DAC) output signal from an analog input signal of the stage. Rather than using a current-mode summation, the CT delaying summation block can be implemented with voltage-mode summation.

Oversampled continuous-time pipeline ADC with voltage-mode summation

A flash analog-to-digital converter (ADC) includes comparators that convert an analog input signal to a digital output signal. Offsets of these comparators introduce noise and can hurt the performance of the ADC. Thus, these comparators are calibrated using calibration codes. Conventional calibration methods determine these calibration codes by removing the ADC from an input signal. Otherwise, it is difficult to distinguish the noise from the signal in the calibration measurement. In contrast, an embodiment can determine the calibration codes while the ADC converts the input signal to a digital signal. Such an embodiment can be achieved by a frequency-domain technique. In an embodiment employing a frequency-domain power meter, an input signal can be removed from the power measurement. This removal enables accurate measurement of in-band noise without having the measurement be corrupted by input signal power.

Frequency-domain ADC flash calibration

Delta-sigma modulators do not handle overload well, and often become unstable if the input goes beyond the full-scale range of the modulator. To provide overload protection, an improved technique embeds an overload detector in the delta sigma modulator. When an overload condition is detected, coefficient(s) of the delta sigma modulator is adjusted to accommodate for the overloaded input. The improved technique advantageously allows the delta sigma modulator to handle overload gracefully without reset, and offers greater dynamic range at reduced resolution. Furthermore, the coefficient(s) of the delta sigma modulator can be adjusted in such a way to ensure the noise transfer function is not affected.

Embedded overload protection in delta-sigma analog-to-digital converters

An analog-to-digital converter (ADC) is a device that can include a reference shuffler and a loop filter. An ADC can achieve better performance with incremental adjustment of a pointer of the reference shuffler, changing coefficients of the loop filter, and storing calibration codes of the ADC in a non-volatile memory. By incrementally adjusting a pointer of the reference shuffler, a calibration can be performed more efficiently than with a random adjustment of the pointer. By temporarily changing the loop filter coefficients, a greater amount of activity can be introduced into the loop filter. This activity can allow the calibration to proceed more efficiently. By storing the calibration codes in a non-volatile memory, a search space for calibration codes can be reduced. Thus, a calibration can occur more quickly, and the calibration itself can be improved.

Flash analog-to-digital converter calibration

Analog-to-digital converters (ADCs) can be used inside ADC architectures, such as delta-sigma ADCs. The error in such internal ADCs can degrade performance. To calibrate the errors in an internal ADC, comparator offsets of the internal ADC can be estimated by computing a mean of each comparator of the internal ADC. Relative differences in the computed means serves as estimates for comparator offsets. If signal paths in the internal ADC are shuffled, the estimation of comparator offsets can be performed in the background without interrupting normal operation. Shuffling of signal paths may introduce systematic measurement errors, which can be measured and reversed to improve the estimation of comparator offsets.

Background flash offset calibration in continuous-time delta-sigma ADCS

For continuous-time multi-stage noise shaping analog to digital converters (CT MASH ADCs), quantization noise cancellation often requires estimation of transfer functions, e.g., a noise transfer function of the front end modulator. To estimate the noise transfer function, a dither signal can be injected in the front end modulator. However, it is not trivial how the dither signal can be injected, since the dither signal can potentially leak to the back end modulator and cause overall noise degradation. To address some of these issues, the dither signal is injected post the flash analog to digital converter (ADC) of the front end modulator. Furthermore, dummy comparator structures can be used to synchronize the dither with the quantization noise of the targeted flash ADC.

Dither injection for continuous-time MASH ADCS

An integrated constant time delay circuit utilized in continuous-time (CT) analog-to-digital converters (ADCs) can be implemented with an RC lattice structure to provide, e.g., a passive all-pass lattice filter. Additional poles created by decoupling capacitors can be used to provide a low-pass filtering effect in some embodiments. A Resistor-Capacitor 'RC' lattice structure can be an alternative to a constant-resistance Inductor-Capacitor 'LC' lattice implementation. ADC architectures benefit from the RC implementation, due to its ease of impedance scaling and smaller area.

RC lattice delay

A system may include a detector, a controller, a shuffler, and a processor. The detector may detect a signal. The controller may control the shuffler based upon the signal. The shuffler may shuffle a plurality of channels at the input of a plurality of processing elements of the processor based upon the signal. The processor may process the signal according to the plurality of channels as configured by the shuffler.

Adaptive element shuffler

A delta-sigma modulator is configured to sense and convert an electromagnetic field into a digital signal. An exemplary delta-sigma modulator includes a sensor component, such as an LC resonator, that is configured to sense the electromagnetic field and generate an input analog signal, where the delta-sigma modulator is configured to convert the input analog signal to the digital signal. Delta-sigma modulator can include an analog-to-digital converter coupled to the sensor component that receives and converts the input analog signal to the digital signal. Delta-sigma modulator can further include a digital-to-analog converter (DAC) coupled to the resonator and the ADC, the DAC configured to receive the digital signal from the ADC and generate a feedback analog signal.

Delta-sigma modulator having sensor front-end

In one aspect, an electrical signal converter is disclosed. The exemplary electrical signal converter may include a plurality of ordered converter elements. Element selection logic may be provided to pseudorandomly select a pointer to a switch matrix, wherein the switch matrix maps converter elements according to a stepwise 'delta-two-maximum pattern.' Advantageously, pseudorandom stepwise delta-two-maximum patterns may be applied both to a first order converter, and to a feedback converter for error correction.

Electrical signal conversion with reduced-distance element rotation

This disclosure describes techniques and methodologies of using passive continuous time (CT) delay line for high-speed CT analog-to-digital converter (ADC) applications. In a continuous-time residual producing stage common to these CT ADCs, a proper delay between the analog input and DAC output is crucial. Specifically, using an inductor-capacitor (LC) lattice based delay element to enable high-performance CT pipeline ADC and CT delta-sigma (&#x394;&#x3a3;) ADC. The use of an LC lattice based delay element provides wide-band group delay for continuous-time signals with well-controlled impedance. This will be an essential circuit component to build a high-performance CT ADCs especially in architectures where the generation of a low-noise and low-distortion residual between the CT signal and its digitized version is needed. LC lattice based delay element enables noise-free, distortion-free wideband delay that is required for high speed continuous-time pipeline ADC and delta-sigma ADC.

LC lattice delay line for high-speed ADC applications

A calibration system for an analog-to-digital converter (ADC) an internal ADC that receives an analog input and converts the analog input to digital multi-bit data. The calibration system also includes a reference shuffling circuit that shuffles reference values of comparators of the internal ADC. Further, the calibration system includes a calibration circuit that calibrates the comparators of the internal ADC. The calibration system includes a digital block that measures an amplitude based on the digital multi-bit data. Additionally, the calibration system includes calibration logic that controls the calibration circuit based on an output of the digital block.

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Toronto, Canada

Trevor Clifford Caldwell