A dual delta-sigma modulator includes a first modulator, a second modulator, and a shared amplifier coupled to the first and second modulators. The first modulator includes an integrator configured to generate a first modulator output signal. The second modulator includes a second integrator configured to generate a second modulator output signal. The shared amplifier is configured to assist the first integrator integrating a difference between a first analog input signal and a first modulator output signal from the first modulator during a first period of time and to assist the second integrator integrate a difference between a second analog input signal and a second modulator output signal from the second modulator during a second period of time.

A signal processing circuit has a first signal loop with a first signal processing block and a first feedback path that extends around the first signal processing block, the first signal processing block having a frequency dependence that causes the first signal loop to generate a passband. A second signal processing block is downstream of the first signal loop. A second feedback path extends from downstream of the second signal processing block to upstream of the first signal processing block. In operation, the first feedback path reinforces a signal in the passband and the second feedback path conditions the signal at an output downstream of the first signal processing block.

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.

The invention provides a system for conversion between analog domain and digital domain with mismatch error shaping, including a DAC, a first injection circuit coupled to the DAC, and a second injection circuit coupled to the DAC. The DAC generates a first analog value in response to a first digital value, and generates a second analog value in response to a second digital value. The first injection circuit enables an analog injection value to be injected to the second analog value when the DAC generates the second analog value, wherein the analog injection value is converted from a digital injection value formed by a subset of bits of the first digital value. The second injection circuit injects the digital injection value to the second digital value, or combines the digital injection value and a related value obtained according to the second analog value.

A delta-sigma Analog-to-Digital Converter (ADC) (IC) which includes an input feed-forward path extending from an input to the ADC to a feed-forward summing circuit disposed between a loop filter and quantizer of the ADC, and a filter disposed in the feed-forward path as an apparatus for improving distortion performance in the delta-sigma ADC. The filter may be a low pass filter, for example, a Resistor-Capacitor (RC) circuit. The filter may have a cut-off frequency outside the ADC's passband. The filtering provided may be continuous-time filtering, even if the delta-sigma ADC is a discrete-time delta-sigma ADC.

A method and apparatus for adjusting a bandwidth of a sigma delta converter by adjusting a reference voltage provided to the sigma delta converter. The apparatus includes a switched capacitor digital-to-analog converter in the feedback loop of the sigma delta modulator. The sigma delta modulator determines the bandwidth mode of the converter and adjusts the reference voltage to deliver high performance functionality. In one embodiment, a multi-bit digital signal is received by the digital-to-analog converter. The reference voltage is provided to multiple capacitive circuits of the digital-to-analog converter and the capacitive circuits are activated and deactivated based on the multi-bit digital signal. The digital-to-analog converter, thus, provides a feedback analog signal using dynamic element matching.

The invention provides a system for conversion between analog domain and digital domain with mismatch error shaping, including a DAC, a first injection circuit coupled to the DAC, and a second injection circuit coupled to the DAC. The DAC generates a first analog value in response to a first digital value, and generates a second analog value in response to a second digital value. The first injection circuit enables an analog injection value to be injected to the second analog value when the DAC generates the second analog value, wherein the analog injection value is converted from a digital injection value formed by a subset of bits of the first digital value. The second injection circuit injects the digital injection value to the second digital value, or combines the digital injection value and a related value obtained according to the second analog value.

For continuous-time multi-stage noise shaping analog-to-digital converters (CT MASH ADCs), quantization noise cancellation often requires accurate estimation of transfer functions, e.g., a noise transfer function of the front end modulator and a signal transfer function of the back end modulator. To provide quantization noise cancellation, digital quantization noise cancellation filters adaptively tracks transfer function variations due to integrator gain errors, flash-to-DAC timing errors, as well as the inter-stage gain and timing errors. Tracking the transfer functions is performed through the direct cross-correlation between the injected maximum length linear feedback shift registers (LFSR) sequence and modulator outputs and then corrects these non-ideal effects by accurately modeling the transfer functions with programmable finite impulse response (PFIR) filters.

The invention provides a system for conversion between analog domain and digital domain with mismatch error shaping, including a DAC, a first injection circuit coupled to the DAC, and a second injection circuit coupled to the DAC. The DAC generates a first analog value in response to a first digital value, and generates a second analog value in response to a second digital value. The first injection circuit enables an analog injection value to be injected to the second analog value when the DAC generates the second analog value, wherein the analog injection value is converted from a digital injection value formed by a subset of bits of the first digital value. The second injection circuit injects the digital injection value to the second digital value, or combines the digital injection value and a related value obtained according to the second analog value.

A dual delta-sigma modulator includes a first modulator, a second modulator, and a shared amplifier coupled to the first and second modulators. The first modulator includes an integrator configured to generate a first modulator output signal. The second modulator includes a second integrator configured to generate a second modulator output signal. The shared amplifier is configured to assist the first integrator integrating a difference between a first analog input signal and a first modulator output signal from the first modulator during a first period of time and to assist the second integrator integrate a difference between a second analog input signal and a second modulator output signal from the second modulator during a second period of time.