Delta-sigma analog-to-digital converter circuit having reduced sampled reference noise

A method of converting an analog signal level to a digital output value, comprising:

• continually integrating the analog signal level with an analog integrator;
• intermittently applying a reference charge to an input of the analog integrator to reduce a magnitude of a voltage of an output of the integrator according to a switching clock and a control indication that controls whether or not the switching clock applies the reference charge in a given period of the switching clock;
• determining when the magnitude of the voltage of the output of the integrator exceeds a threshold voltage;
• and
• generating the control indication in response to a result of the determining, wherein the switching clock applies the reference charge to the analog integrator in response to a result of the determining.

An analog-to-digital converter circuit, comprising:

• an integrator for receiving an input signal to be converted to a digital representation of the input signal according to a sampling clock;
• a reference circuit for restoring the integrator toward a zero value output in order that the integrator remain in linear operation;
• and
• a control circuit for controlling operation of the reference circuit switching of the reference switched-capacitor circuit such that the reference circuit is not operated at each sampling clock but intermittently according to an indication of a magnitude of the output of the integrator.

A method of converting an analog signal level to digital output values, comprising:

• continually integrating the analog signal level with an analog integrator;
• restoring the analog integrator toward a zero value output in order that the analog integrator remain in linear operation;
• and
• determining when the magnitude of an output of the analog integrator exceeds a threshold voltage, wherein the restoring is performed only in response to the determining that the output of the analog integrator has exceeded the threshold voltage.