An analog-to-digital converting apparatus includes a first stage converter which performs a first analog-to-digital conversion on an input analog signal during a first stage period, a second stage converter which receives a first residue from the first stage converter amplified by a first gain and which performs a second analog-to-digital conversion during a second stage period, and a recombination logic circuit which combines a first output signal from the first stage converter and a second output signal from the second stage converter into an output digital signal that corresponds to the input analog signal. The second stage converter generates a second stage feedback signal obtained by amplifying the second output signal by the first gain during a first sub-cycle in the second stage period, and generates a second output signal of a second sub-cycle subsequent to the first sub-cycle based on the second stage feedback signal.

Systems and methods are provided for increasing efficiency of excess loop delay compensation in delta-sigma analog-to-digital converters. In some examples, systems and methods are provided for reducing total capacitance in an embedded excess loop delay compensation digital-to-analog converter (DAC) in a quantizer for a continuous time delta-sigma ADC. In other examples, the excess loop delay compensation DAC can be a current domain DAC, a charge domain DAC, or a voltage domain DAC. Additionally, methods are provided for digitally controlling the gain of an excess loop delay DAC. Furthermore, methods are provided to calibrate a gain mismatch between a main successive approximation register DAC and an excess loop delay DAC. The systems and methods provided herein improve performance of continuous time delta-sigma ADCs. Continuous time delta-sigma ADCs are high precision and power efficient ADCs, often used in audio playback devices and medical devices.

A phase-locked loop (PLL) may include a phase-frequency detector (PFD), a phase interpolation (PI)-based sampler, a loop filter, a voltage-controlled oscillator (VCO), and a fractional frequency divider. The PFD output corresponds to a phase error between a reference clock signal and a feedback signal. The PI-based sampler produces a slope signal in response to the PFD output, and adjusts the slope signal in response to a quantization error correction indication. The PI-based sampler also samples the slope signal. The loop filter produces a VCO control signal in response to a sampled slope signal. The VCO control signal controls the VCO frequency. The fractional frequency divider circuit divides the frequency of the VCO output signal and also determines the quantization error correction corresponding to the quantization error introduced by fractional division of the frequency of the VCO output signal.

A circuit includes a transconductance stage having first and second outputs. The circuit also includes a comparator having first and second inputs. The first input is coupled to the first output, and the second input is coupled to the second output. The comparator includes first through fifth transistors and a pair of cross-coupled transistors. The pair of cross-coupled transistors is coupled to the second current terminals of the first and second transistors. The second current terminal of the third transistor is coupled to the second current terminal of the first transistor, and the first current terminals of the first, second, and third transistors are coupled together. The second current terminals of the fourth and fifth transistors are coupled together and to the control input of the third transistor.

Disclosed is an integrated circuit, which includes a DTC block including DTCs, receiving a first reference signal and a first division signal, and outputting a second reference signal and a second division signal based on the first reference signal, the first division signal, and control codes, a TDC comparing phases of the second reference signal and the second division signal and outputting a comparison signal, a digital loop filter filtering the comparison signal, an oscillator generating an output signal based on the filtered comparison signal, a delta-sigma modulator outputting a first signal and a quantized noise signal based on first and second division ratio signals, a divider dividing a frequency of the output signal based on the first signal and outputting the first division signal, and a probability modulator generating the control codes based on the quantized noise signal. Probability density functions of the control codes are time-invariant.

Disclosed is an integrated circuit, which includes a DTC block including DTCs, receiving a first reference signal and a first division signal, and outputting a second reference signal and a second division signal based on the first reference signal, the first division signal, and control codes, a TDC comparing phases of the second reference signal and the second division signal and outputting a comparison signal, a digital loop filter filtering the comparison signal, an oscillator generating an output signal based on the filtered comparison signal, a delta-sigma modulator outputting a first signal and a quantized noise signal based on first and second division ratio signals, a divider dividing a frequency of the output signal based on the first signal and outputting the first division signal, and a probability modulator generating the control codes based on the quantized noise signal. Probability density functions of the control codes are time-invariant.

A quad signal generator circuit generates four 2.sup.N−1 bit control signals in response to a sampling clock and a 2.sup.N−1 bit thermometer coded signal. A digital-to-analog converter (DAC) circuit has 2.sup.N−1 unit resistor elements, with each unit resistor element including four switching circuits controlled by corresponding bits of the four 2.sup.N−1 bit control signals. Outputs of the 2.sup.N−1 unit resistor elements are summed to generate an analog output signal. The quad signal generator circuit controls generation of the four 2.sup.N−1 bit control signals such that all logic states of bits of the four 2.sup.N−1 bit control signals remain constant for at least a duration of one cycle of the sampling clock. The analog output signal may be a feedback signal in a sigma-delta analog-to-digital converter (ADC) circuit that includes a multi-bit quantization circuit operating to quantize a filtered loop signal to generate the 2.sup.N−1 bit thermometer coded signal.

An analog-to-digital converting apparatus includes a first stage converter which performs a first analog-to-digital conversion on an input analog signal during a first stage period, a second stage converter which receives a first residue from the first stage converter amplified by a first gain and which performs a second analog-to-digital conversion during a second stage period, and a recombination logic circuit which combines a first output signal from the first stage converter and a second output signal from the second stage converter into an output digital signal that corresponds to the input analog signal. The second stage converter generates a second stage feedback signal obtained by amplifying the second output signal by the first gain during a first sub-cycle in the second stage period, and generates a second output signal of a second sub-cycle subsequent to the first sub-cycle based on the second stage feedback signal.

A delta-sigma modulator generates a bit stream signal from an analog signal by operating according to a modulation period including a sampling period and a filtering period and includes a digital-to-analog converter (DAC) configured to generate a charge signal according to one of a first reference voltage and a second reference voltage according to the bit stream signal during the sampling period and to output a signal generated according to the charge signal and the other of the first reference voltage and the second reference voltage; a loop filter configured to charge a sampling signal corresponding to the analog signal during the sampling period and to filter an output from the DAC and a signal generated according to the sampling signal during the filtering period; and a quantizer configured to generate the bit stream signal according to an output from the loop filter in the modulation period.

A fractional-N phase-locked loop (PLL) has a time-to-voltage converter with second order non linearity. The time-to voltage-converter provides an analog error signal indicating a phase difference between the reference clock signal with a period error and a feedback signal supplied by a fractional-N feedback divider. The spur results in quantization noise associated with the fractional-N feedback divider being frequency translated. To address the frequency translated noise, a spur cancellation circuit receives a residue signal indicative of the quantization noise and a spur signal indicative of the spur. The non-linearity of the time-to-voltage converter is mimicked digitally through terms of a polynomial generated to cancel the noise. The generated polynomial is coupled to a delta sigma modulator that controls a digital to analog converter that adds/subtracts a voltage value to/from the error signal to thereby cancel the quantization noise including the frequency translated quantization noise.