Variable sample-rate DAC/ADC/converter system

A digital oversampling noise-shaping system comprising:

• an interpolator, that receives digital input samples at an input sample rate and, responsive to a noise-shaped clock signal, upsamples the digital input samples at a variable upsampling rate;
• a digital noise-shaped clock signal generating circuit, including a DCO operating at the fixed master clock rate, that receives a digital input clock signal and produces the noise-shaped clock signal having an average rate equal to a multiple of the input sample rate, the DCO including a first sigma-delta modulator that operates at a variable rate;
• and
• a digital noise-shaping circuit, coupled to the interpolator, that performs digital noise-shaping on the upsampled input samples at a fixed master clock rate.

A method of upsampling and noise-shaping digital input samples comprising the steps of:

• receiving a digital input clock signal having at an input sample rate;
• producing a noise-shaped clock signal having a variable rate with an average rate equal to a multiple of the input sample rate;
• the step of producing including operating a sigma-delta modulator at a variable rate to produce the noise-shaped clock signal;
• responsive to the noise-shaped clock signal, upsampling the digital input samples at the variable rate;
• and
• performing digital noise-shaping on the upsampled input samples.

A digital decimation system comprising:

• a digital noise-shaped clock signal generating circuit, including a DCO operating at a fixed master clock rate, that receives an input clock signal at an output sample rate and produces a noise-shaped clock signal having a variable rate with an average rate equal to a multiple of the output sample rate, wherein the DCO includes a sigma-delta modulator that operates at a variable rate;
• and
• a resampler, coupled to the clock signal generating circuit, that resamples oversampled input samples at the variable rate;
• and
• a decimator, coupled to the clock signal generating circuit and the resampler, that receives the resampled input samples at the variable rate and produces output samples at a rate that is a fixed sub-multiple of the variable rate.