Noise shaping successive approximation register analog-to-digital converter

A successive approximation register (SAR) loop configured to perform noise shaping in an analog-to-digital converter (ADC), the SAR loop comprising:

• a comparator including first and second input terminals configured to receive first and second input signals, and an output terminal configured to output an output signal;
• a SAR logic unit coupled to the output terminal of the comparator and configured to perform a noise shaping operation on the output signal until only a residue signal is left on the first input terminal;
• a storage module configured to store the residue signal during a first phase of the noise shaping operation, the storage module configured to receive an analog input signal and remove the residue signal from the analog input signal in a second phase of the noise shaping operation to output a new first input signal to the first input terminal,
• wherein the storage module comprises a residue capacitor having first and second nodes;
• and a first buffer coupled to the first input terminal and configured to buffer and store the residue signal on the residue capacitor;
• a first switch coupled to the first buffer and the first node of the residue capacitor, the first switch configured to enable storage of the residue signal on the residue capacitor during the first phase of the noise shaping operation;
• and
• a second switch coupled to the first input terminal and the second node of the residue capacitor, the second switch configured to place the residue capacitor in series with the analog input signal to remove the residue signal from the analog input signal in the second phase of the noise shaping operation.

A sigma-delta modulator (SDM) comprising:

• a loop filter configured to receive and integrate an input signal and output a first integrated signal;
• and
• a quantizer including:
• a noise shaping module configured to receive the first integrated signal and output a quantization error signal at a first input terminal in a noise shaping operation;
• a sample-and-hold module configured to store the quantization error signal during a first phase of the noise shaping operation, the sample-and-hold module configured to receive a second integrated signal from the loop filter and remove the quantization error signal from the second integrated signal in a second phase of the noise shaping operation,
• wherein the sample-and-hold module comprises a first residue capacitor having first and second nodes;
• and a first buffer coupled to the first input terminal and configured to buffer and store the quantization error signal on the first residue capacitor;
• a first switch coupled to the first buffer and the first node of the residue capacitor, the first switch configured to enable storage of the quantization error signal on the residue capacitor during the first phase of the noise shaping operation;
• and
• a second switch coupled to the first input terminal and the second node of the residue capacitor, the second switch configured to place the residue capacitor in series with the second integrated signal to remove the quantization error signal from the second integrated signal in the second phase of the noise shaping operation.

An apparatus for performing noise shaping in an analog-to-digital converter (ADC), the apparatus comprising:

• means for comparing a first received input signal to a second received input signal using a noise shaping module;
• means for outputting a digital output signal and a residue signal in a first phase of a noise shaping operation;
• means for storing the residue signal during the first phase of the noise shaping operation in a storage module,
• wherein the means for storing comprises:
• a residue capacitor having first and second nodes;
• and a buffer configured to buffer the residue signal on the residue capacitor;
• means for removing the residue signal from an analog input signal in a second phase of the noise shaping operation to output a new first input signal;
• first means for switching coupled to the buffer and the first node of the residue capacitor, the first means for switching configured to enable storage of the residue signal on the residue capacitor during the first phase of the noise shaping operation;
• and
• second means for switching coupled to the second node of the residue capacitor, the second means for switching configured to place the residue capacitor in series with the analog input signal to remove the residue signal from the analog input signal in the second phase of the noise shaping operation.