Increased noise performance using quantizer code suppression

A method comprising:

• filtering an input signal to generate an intermediate signal responsive to the input signal by a loop filter;
• quantizing with a multi-bit quantizer the intermediate signal into a quantized output signal which is fed back as an input to the loop filter, wherein the quantizer is configured to operate in at least two modes comprising:
• a normal mode in which, for each sample of the intermediate signal, the multi-bit quantizer generates a corresponding sample having a value selected from a set of a plurality of quantization levels;
• and
• a code suppression mode in which, for each sample of the intermediate signal, the multi-bit quantizer generates a corresponding sample having a value selected from a subset of the set of a plurality of quantization levels.

A digital-to-analog converter comprising:

• a digital delta-sigma modulator comprising:
• a loop filter having a loop filter input configured to receive an input signal and generate an intermediate signal responsive to the input signal;
• a multi-bit quantizer configured to quantize the intermediate signal into a quantized output signal which is fed back as an input to the loop filter and further configured to operate in at least two modes comprising:
• a normal mode in which, for each sample of the intermediate signal, the multi-bit quantizer generates a corresponding sample having a value selected from a set of a plurality of quantization levels;
• and
• a code suppression mode in which, for each sample of the intermediate signal, the multi-bit quantizer generates a corresponding sample having a value selected from a subset of the set of a plurality of quantization levels;
• and
• a duty cycle calculator configured to, based on the quantized output signal, generate a pulse-width modulated signal equivalent to the input signal.