Method and apparatus for converting A/D nonlinearities to random noise

A method of reducing the effects of component mismatch in an analog to digital (A/D) converter having a plurality of capacitors each having a capacitance of approximately C, said plurality of capacitors coupled to a plurality of switches, said method comprising the steps of:

• defining at least first and second groups of said capacitors, said first group comprising x capacitors and said second group comprising y capacitors;
• selectively coupling a first of said switches to said first group and a second of said switches to said second group;
• switching each of said plurality of capacitors into said first group or said second group;
• controlling said switching of said capacitors such that the time-averaged ratio of the amount of time one of said capacitors is coupled to said first of said switches compared to the amount of time said one of said capacitors is coupled to said second of said switches is approximately equal to x/y.

A circuit comprising:

• a plurality of impedance elements, each having an impedance which is approximately equal;
• a first switch coupled to a first number x of said elements;
• a second switch coupled to a second number y of said elements;
• a switching matrix coupled to said elements and to said first and second switches for selectably coupling said plurality of impedance elements to each of said first and second switches such that the time-averaged ratio of the amount of time one of said elements is coupled to said first switch compared to the amount of time said one of said elements is coupled to said second switch is approximately equal to x/y.

A method of switching elements in a circuit having a plurality of impedance elements, each having an impedance which is approximately equal, coupled to a plurality of switches, said method comprising the steps of:

• defining at least first and second groups of impedance elements, said first group comprising x impedance elements and said second group comprising y impedance elements;
• selectively coupling a first of said switches to said first group and a second of said switches to said second group;
• switching each of said plurality of impedance elements into said first group or said second group;
• controlling said switching of said impedance elements, such that the time averaged ratio of the amount of time one of said impedance elements is coupled to said first of said switches compared to the amount of time said one of said impedance elements is coupled to said second of said switches is approximately equal to x/y.