An asynchronous successive approximation register analog-to-digital converter (SAR ADC), which utilizes one or more overlapping redundant bits in each digital-to-analog converter (DAC) code word, is operable to generate an indication signal that indicates completion of each comparison step and indicates that an output decision for each comparison step is valid. A timer may be initiated based on the generated indication signal. A timeout signal may be generated that preempts the indication signal and forces a preemptive decision, where the preemptive decision sets one or more remaining bits up to, but not including, the one or more overlapping redundant bits in a corresponding digital-to-analog converter code word for a current comparison step to a particular value. For example, the one or more remaining bits may be set to a value that is derived from a value of a bit that was determined in an immediately preceding decision.

A Successive Approximation Register, SAR, Analog to Digital Converter, ADC, (50) achieves high speed and accuracy by (1) alternating at least some decisions between sets of comparators having different accuracy and noise characteristics, and (2) unevenly allocating redundancy (in the form of LSBs of range) for successive decisions according to the accuracy/noise of the comparator used for the preceding decision. The redundancy allocation is compensated by the addition of decision cycles. Alternating between different comparators removes the comparator reset time (treset) from the critical path, at least for those decision cycles. The uneven allocation of redundancy—specifically, allocating more redundancy to decision cycles immediately following the use of a lower accuracy/higher noise comparators—compensates for the lower accuracy and prevents the need for larger redundancy (relative to the full-scale range of a decision cycle) later in the ADC process.

An apparatus is disclosed for analog-to-digital conversion. In an example aspect, the apparatus includes an analog-to-digital converter (ADC). The ADC includes a reference-crossing detector having an input and an output. The ADC also includes a ramp generator coupled between the output of the reference-crossing detector and the input of the reference-crossing detector. The ADC further includes a voltage shifter coupled between the output of the reference-crossing detector and the input of the reference-crossing detector.

Systems and methods related to successive approximation register (SAR) analog-to-digital converters (ADCs) are provided. A method for performing successive approximation registers (SAR) analog-to-digital conversion includes comparing, using a comparator, a first digital-to-analog (DAC) output voltage to a sampled analog input voltage to generate a comparison result including a first positive output and a first negative output; and gating, using gating logic circuitry, at least one of the first positive output or the first negative output of the comparator to next logic circuitry, the gating based at least in part on a digital feedback comprising information associated with at least one of an opposite polarity of the first positive output or an opposite polarity of the first negative output.

Herein disclosed are some examples of metastability detectors and compensator circuitry for successive-approximation-register (SAR) analog-to-digital converters (ADCs) within delta sigma modulator (DSM) loops. A metastability detector may detect metastability at an output of a SAR ADC and compensator circuitry may implement a compensation scheme to compensate for the metastability. The identification of the metastability and/or compensation for the metastability can avoid detrimental effects and/or errors to the DSM loops that may be caused by the metastability of the SAR ADCS.

A successive-approximation analog-to-digital converter includes a sampling circuit for sampling an analog input signal to acquire a sampled voltage, and a regenerative comparator for comparing the sampled voltage with a succession of reference voltages to generate, for each reference voltage, a decision bit indicating the comparison result. The converter also includes a digital-to-analog converter which is adapted to generate the succession of reference voltages, in dependence on successive comparison results in the comparator, to progressively approximate the sampled voltage. The regenerative comparator comprises an integration circuit for generating output signals defining the decision bits, and a plurality of regeneration circuits for receiving these output signals. The regeneration circuits are operable, in response to respective control signals, to store respective decision bits defined by successive output signals from the integration circuit.

A circuit portion comprising a clock domain is disclosed. A first clock is arranged to clock components in the clock domain. An analogue to digital converter is clocked by a second clock with a duty cycle. The second clock is derived from the first clock. The analogue to digital converter is arranged to output a feedback signal upon finishing a conversion of a sample, and the feedback signal is arranged to control the duty cycle.

A pipeline analog to digital converter includes converter circuitries and a calibration circuitry. The converter circuitries sequentially convert an input signal into first digital codes. A first converter circuitry in the converter circuitries performs a quantization according to a first signal to generate a first corresponding digital code in the first digital codes, and the first signal is a signal, which is processed by the first converter circuitry, of the input signal and a previous stage residue signal. The calibration circuitry combines the first digital codes to output a second digital code, detects whether the quantization is completed to generate first and second valid signals, and determines whether to set the second digital code to be a first predetermined digital code or a second predetermined digital code according to the first and the second valid signals. The second valid signal is a delay signal of the first valid signal.

An analog-to-digital converter (ADC) is described. This ADC includes a conversion circuit with multiple bit-conversion circuits. During operation, the ADC may receive an input signal. Then, the conversion circuit may asynchronously perform successive-approximation-register (SAR) analog-to-digital conversion of the input signal using the bit-conversion circuits, where the bit-conversion circuits to provide a quantized representation of the input signal. For example, the bit-conversion circuits may asynchronously and sequentially perform the SAR analog-to-digital conversion to determine different bits in the quantized representation of the input signal. Moreover, the ADC may selectively perform self-calibration of a global delay of the bit-conversions circuits. Note that the timing self-calibration may be iterative and subject to a constraint that a maximum conversion time is less than a target conversion time.

A SAR ADC and an electronic device are disclosed. The SAR ADC includes a read clock generation circuit, configured to connect to a first output terminal and a second output terminal of a dynamic comparator, and generate a read clock signal for reading a first or a second comparison result based on the first and the second comparison result received from the dynamic comparator. The invention reads the comparison result using the read clock signal generated by grabbing the output of the comparator, and can improve the overall analog-to-digital conversion speed of the SAR ADC. Further, the present invention can detect the occurrence of metastable state of the comparator by judging that the output of the comparator has no pulse, and read the comparison result based on the backup clock generated by the operating clock of the comparator.