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.

An analog-to-digital converting device includes N-stage first analog-to-digital converters (ADCs), a second ADC, a first calibration circuit, a data recovery circuit and an output circuit. The N-stage first ADCs has a first sampling frequency that is (N+1)/N times of a second sampling frequency, and converts an input signal into first quantized outputs. The second ADC has the second sampling frequency, and converts the input signal into a second quantized output. The first calibration circuit calibrates offsets of the first quantized outputs and the second quantized output to generate third quantized outputs and a fourth quantized output. The data recovery circuit outputs, by the second sampling frequency, one of the third quantized outputs as a fifth quantized output, and subtracts the fifth quantized output from the fourth quantized output to generate output data. The output circuit generates an output signal according to the third quantized outputs and the output data.

Circuits and methods for maintaining loop stability and good load regulation in low loop gain LDO regulator circuits. Embodiments encompass LDO regulator circuits that include an offset error correction circuit that generates an opposing voltage V.sub.OFFSET as a function of load current to substantially cancel out variations in V.sub.OUT that would otherwise occur due to load regulation limitations of the LDO regulator circuits. Embodiments use V.sub.OFFSET to imbalance currents in differential paths in a last-stage LDO error-amplifier so that an offset is propagated to a pair of inputs to the error-amplifier, thereby altering the output voltage V.sub.OUT to a corrected value. Benefits include improved LDO load regulation even when feedback loop gain is low, the available of both digital and analog implementations, high LDO accuracy and less variation of the output voltage V.sub.OUT, and suitability for implementation in integrated circuits for applications such as high precision power supplies.

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.

A background offset calibration system for an analog signal comparator provides low offset without compromising tracking bandwidth. The comparator includes a preamplifier and a decision latch. A switching selectively couples outputs of an analog circuit to the inputs of the preamplifier stage. A state control logic alternatively operates the system in a first phase in which the analog circuit acquires an input signal while the comparator is calibrated, and a second phase in which a comparison is performed by the comparator. In the first phase, the switching circuit disconnects the outputs of the analog circuit from the preamplifier stage and applies a common mode reference to the inputs of the preamplifier. An offset correction circuit determines correction changes from a history of states of the decision latch across multiple sampling cycles. The offset correction circuit adjusts a threshold voltage of the decision latch by applying the correction changes.

A fingerprint signal processing system for a fingerprint sensor includes a calibration control circuit, a register circuit, a decode circuit and a normalization circuit. The calibration control circuit is configured to receive a background calibration control signal and an image signal from the fingerprint sensor, and convert the image signal into a plurality of digital signals according to a plurality of offsets. When the background calibration control signal is at a high level, the calibration control circuit is configured to read a plurality of calibration parameters from the register circuit.

An N-channel interleaved Analog-to-Digital Converter (ADC) has a variable delay added to each ADC's input sampling clock. The variable delays are each programmed by a Successive-Approximation-Register (SAR) during calibration to minimize timing skews between channels. In each channel the ADC output is filtered, and a product derivative correlator generates a product derivative factor for correlation to two adjacent ADC channels. A matrix processor arranges the product derivative factors from the product derivative correlators into a matrix that is multiplied by a correlation matrix. The correlation matrix is a constant generated from an N×N shift matrix. The matrix processor outputs a sign-bit vector. Each bit in the sign-bit vector determines when tested SAR bits are set or cleared to adjust a channel's variable delay. Sampling clock and component timing skews are reduced to one LSB among all N channels.

An N-channel interleaved Analog-to-Digital Converter (ADC) has a variable delay added to each ADC's input sampling clock. The variable delays are each programmed by a Successive-Approximation-Register (SAR) during calibration to minimize timing skews between channels. Each channel receives a sampling clock with a different phase delay. The sampling clocks are overlapping multi-phase clocks rather than non-overlapping. Overlapping the multi-phase clocks allows the sampling pulse width to be enlarged, providing more time for the sampling switch to remain open and allow analog voltages to equalize through the sampling switch. Higher sampling-clock frequencies are possible than when non-overlapping clocks are used. The sampling clock is boosted in voltage by a bootstrap driver to increase the gate voltage on the sampling switch, reducing the ON resistance. Sampling clock and component timing skews are reduced to one LSB among all N channels.

A method for removing low frequency offset components from a digital data stream includes receiving, at an input of an analog-to-digital converter (ADC), an analog input signal from one or more analog front end components. The analog input signal has an associated low frequency offset due, at least in part, to the analog front end components. The method also includes generating, at an output of the ADC, a digital data stream representative of the analog input signal. The digital data stream having an associated low frequency offset due, at least in part, to the analog front end components and/or the ADC. One or more low pass infinite impulse response (IIR) filters are applied to the digital data stream to detect the low frequency offset components in the digital data stream, and generate a filtered output signal with only the low frequency offset components present. A corrected digital data stream without the low frequency offset components is generated in response thereto, for example, by taking the difference of the filtered output signal from the digital data stream.

A method of operating a pipelined analog-to-digital converter (ADC) having a plurality of output stages includes: performing a first calibration process for the pipelined ADC to update a parameter vector of the pipelined ADC, where components of the parameter vector are used for correcting nonlinearity of the pipelined ADC, where performing the first calibration process includes: providing an input signal to the pipelined ADC; converting, by the pipelined ADC, the input signal into a first digital output; providing a scaled version of the input signal to the pipelined ADC, where the scaled version of the input signal is generated by scaling the input signal by a scale factor; converting, by the pipelined ADC, the scaled version of the input signal into a second digital output; and calibrating the pipelined ADC using the first digital output and the second digital output.