Analog Devices Global

Analog Devices International Unlimited Company

Analog Devices Global Unlimited Company

Analog Devices Technology

Zhao Li

Trevor Clifford Caldwell

Hajime Shibata

David Nelson Alldred

Victor Kozlov

Yunzhi Dong

Richard E Schreier

Prawal Man Shrestha

Jialin Zhao

Christopher Mayer

Wenhua William Yang

Kevin Glenn Gard

Donald W Paterson

Shipra Bhal

Ali Sheikholeslami

David J McLaurin

David J Mclaurin

Jose Barreiro Silva

Sharvil Pradeep Patil

Asha Ganesan

Yue Yin

David Alldred

Trevor Caldwell

In one aspect, a transfer function (TF) estimation circuit configured to generate an estimate of a TF undergone by signals between an input of a digital-to-analog converter (DAC) of a feedforward path of a continuous-time (CT) stage of an analog-to-digital converter (ADC) and an output of a backend ADC of the ADC is disclosed. The TF estimation circuit includes one or more circuits configured to generate a first cross-correlation output by cross-correlating digital versions of signals based on a test signal provided to the CT stage and an output signal of the backend ADC, generate a second cross-correlation output by cross-correlating digital versions of signals based on the test signal and an output signal of a quantizer of the feedforward path of the CT stage, and generate the estimate of the TF based on the first and second cross-correlation outputs.

Digital estimation of transfer functions in continuous-time analog-to-digital converters

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

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

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

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

An analog-to-digital converter (ADC) can include a continuous-time delta sigma modulator and calibration logic. The calibration logic can calibrate direct feedback and flash clock delay coefficients of the continuous-time delta-sigma modulator without interrupting the normal operations of the ADC (e.g., in situ). Thus, the calibration logic can rectify performance and stability degradation by calibrating suboptimal coefficients.

System and method of improving stability of continuous-time delta-sigma modulators

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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Zhao Li