Techniques for power efficient oversampling successive approximation register

A method for noise-shaping in a successive approximation register analog-to-digital converter comprises:

• receiving an input analog signal at a successive approximation register (SAR),
• converting the input analog signal to a digital signal at the SAR,
• switching a DAC to convert the digital signal to a present analog residue for a present conversion cycle,
• processing a previous analog residue from a previous conversion cycle at a filter to generate a processed previous analog residue,
• outputting the processed previous analog residue to the SAR,
• summing the processed previous analog residue and the present analog residue and generating a summer output, and
• comparing the summer output and a first reference signal and generating a comparator output.

A system for a successive approximation register analog-to-digital-converter having a noise transfer function comprising:

• a successive approximation register (SAR) for receiving an analog input signal and outputting a digital decision;
• a first digital-to-analog converter (DAC) and logic circuitry for converting the digital decision of the SAR to a present analog residue for a present conversion cycle;
• a second DAC for processing a previous analog residue from a previous conversion cycle, and storing a processed previous analog residue at the end of the previous conversion cycle;
• a filter for receiving the processed previous analog residue from the second DAC and generating a filter output;
• and
• a comparator for comparing the filter output and the present analog residue, and generating a comparator output.