An image sensor may contain an array of imaging pixels. Each pixel column outputs signals that are read out using a successive approximation register (SAR) analog-to-digital converter (ADC). The SAR ADC may include at least first and second input sampling capacitors, a comparator, a capacitive digital-to-analog converter (CDAC), and associated control circuitry. If desired, the SAR ADC may include a bank of more than two input sampling capacitors alternating between sampling and conversion. The first capacitor may be used to sample an input signal while conversion for the second capacitor is taking place. Prior to conversion, an input voltage of the comparator and an output voltage of the CDAC may be initialized. During conversion of the signal on the first capacitor, the first capacitor is embedded within the SAR ADC feedback loop to prevent charge sharing between the input sampling capacitor and the CDAC, thereby mitigating potential capacitor mismatch issues.

An integrator and an analog-to-digital converter are provided. The analog-to-digital converter includes the integrator, a comparison circuit and a control logic circuit. The integrator includes an operational amplifier, offset capacitors, input capacitors, integral capacitors and controllable switches. The input capacitors and the integral capacitors are connected to the operational amplifier via controllable switches, so that the integrator operates in various operation modes. Operation states of the offset capacitors in a first phase and a second phase of an operation cycle are controlled by switching on or off the controllable switches. Therefore, an offset voltage of the integrator is eliminated, and conversion efficiency and conversion accuracy of the analog-to-digital converter is improved.

An A/D conversion circuit includes a comparison-reference-signal generator section configured to generate a comparison reference signal synchronized with a sampling clock signal, a comparator configured to compare a voltage of an input signal and a voltage of the comparison reference signal to thereby generate a trigger signal, a time to digital converter configured to calculate a first time digital value, and a digital-signal generator section configured to generate, based on the first time digital value and a second time digital value, a digital signal corresponding to the voltage of the input signal. The first time to digital converter includes a state transition section configured to start transition of a state based on the trigger signal and output state information, and a weight operation section configured to, in synchronization with the reference clock signal, perform, on a value based on the state information, weighting corresponding to time elapsing and perform a predetermined arithmetic operation to thereby calculate the first time digital value corresponding to the number of transition times of the state.

Disclosed herein are some examples of analog-to-digital converters (ADCs) that can perform auto-zeroing with amplifying a signal for improvement of a signal-to-noise ratio. The ADCs may produce a first digital code to represent an analog input signal and a second digital code based on a residue from the first digital code, and may combine the first digital code and the second digital code to produce a digital output code to represent the analog input signal. The ADC may utilize a first observation and a second observation of an analog residue value representing the residue to produce the second digital code.

A digital-to-time converter (DTC) converts a digital code into a time delay using a capacitor digital-to-analog converter (CDAC) that functions as a charging capacitor. The DTC includes a switched capacitor voltage-to-current converter for the formation of a charging current (or a discharging current) for charging (or for discharging) the charging capacitor responsive to a triggering clock edge that begins the time delay. A comparator compares a voltage on the charging capacitor to a threshold voltage to determine an end of the time delay.

An successive approximation register analog-to-digital converter is provided. The successive approximation register analog-to-digital converter includes a digital-to-analog converter, a successive approximation register, a comparator, and a threshold voltage determining unit. In this context, the threshold voltage determining unit is configured to dynamically determine the threshold voltage of the comparator on the basis of the input signal of the digital-to-analog converter or the output signal of the comparator.

A multi-stage pipelined Analog-to-Digital Converter (ADC) has an offset correction circuit embedded in the residue amplifier between stages. The offset corrector has a low-pass filter that filters the output of the residue amplifier, and the filtered offset is amplified and stored on an offset capacitor during an autozeroing phase of the residue amplifier. During an amplify phase of the residue amplifier, switches disconnect the amplifier from the offset capacitor and instead ground the input of the offset capacitor, and other switches connect the output terminal of the offset capacitor to the input of the residue amplifier. The offset stored on the offset capacitor is combined with the residue voltage from the first ADC stage's capacitor array and applied to an input of the residue amplifier to effectively subtract the detected offset. Two offset capacitors and sets of switches can be used to implement a differential offset corrector.

An apparatus includes a plurality of binary weighted capacitors coupled between a first input terminal of a comparator and a plurality of signal buses, wherein the plurality of binary weighted capacitors has a binary weight increasing by two times from a first capacitor to an (N−K)th capacitor, and a constant binary weight from the (N−K)th capacitor to a (N−K−2+2.sup.(K+1))th capacitor, an offset voltage generator configured to generate a digitally controlled offset voltage having 2.sup.(K+1) steps fed into a second input terminal of the comparator, and a successive approximation logic block configured to receive an output signal of the comparator, and generate an N-bit control signal for controlling the plurality of binary weighted capacitors.

Analog-to-digital converter circuitry includes comparator circuitry, capacitor analog-to-digital converter circuitry (CDA), and successive approximation register (SAR) circuitry. The comparator circuitry includes a non-inverting input and an inverting input to selectively receive a differential voltage signal, and an output. The CDAC circuitry includes a first capacitor network having a first plurality of capacitors. A first capacitor of the first plurality of capacitors includes a first terminal connected to the non-inverting input and a second terminal selectively connected to a first voltage potential and a second voltage potential. The first voltage potential is greater than the second voltage potential. The SAR circuitry is connected to the output and the first capacitor network, and connects, during a first period, the second terminal of the first capacitor to the second voltage potential. The non-inverting input and the inverting input are connected to the differential voltage signal during the first period.

Disclosed herein are related to systems and methods for a successive approximation analog to digital converter (SAR ADC). In one aspect, the SAR ADC includes a calibration circuit configured to receive some or all of the plurality of bits corresponding to the input voltage and accumulates or averages at least some of the bits corresponding to the input voltage. The calibration circuit is configured to provide a first offset signal to control a first offset associated with a first comparator, a second offset signal to control a second offset associated with a second comparator, or reduce an offset difference associated with the first offset and the second offset.