High resolution analog current-to-frequency converter

Claim 1

An analog-to-digital converter with an analog input and a digital signal output comprising: current controlled integrating means having a non-inverting input at ground, an inverting input for receiving an analog signal over the analog input, and a voltage output; timing means which receives a system clock signal and outputs a plurality of timing signals which are dependent on cycles of the system clock; a ramp signal generating means which cyclically outputs a ramping signal in response to one of the plurality of timing signals; comparing means which compares the output voltage and the ramping signal and outputs a pulse with a width proportional to the magnitude of the analog signal; switching means which receives the pulse from the comparator means and is in electrical contact with said timing means; feedback means connected to said switching means for providing positive or negative current balancing pulses at the inverting input of said current controlled integrator such that over time a residual charge left on the integrating means is indicative of the magnitude of the analog signal; and digital encoding means connected to said switching means for converting the pulse output from said comparator means through said switching means into a digital output.

Claim 17

A method of analog-to-digital conversion comprising the steps of: receiving an analog signal; integrating the analog signal so as to generate a first ramping signal with a slope proportional to the analog signal magnitude; providing a second ramping signal of known slope which periodically resets and begins again after reaching a predetermined magnitude; comparing the first and second ramping signal during the predetermined period time and generating a first pulse width while the first ramping signal is greater than the second ramping signal and generating a second pulse width while the first ramping signal is less than the second ramping signal; translating the first and second pulse widths into a digital output indicative of the magnitude and polarity of the analog signal; and periodically adding pulses of negative and positive current to the analog signal to provide current balancing for integration of the analog signal, where the addition of the positive and negative current is controlled by the size of the first and second pulse widths.

Claim 18

A method of analog-to-digital conversion comprising the steps of: receiving an analog signal; integrating the analog signal so as to generate a first ramping signal with a slope proportional to the analog signal magnitude; providing a second ramping signal of known slope which periodically resets and begins again after reaching a predetermined magnitude; comparing the first and second ramping signal during the predetermined period time and generating a first pulse width while the first ramping signal is greater than the second ramping signal and generating a second pulse width while the first ramping signal is less than the second ramping signal; translating the first and second pulse widths into a digital output indicative of the magnitude and polarity of the analog signal; and periodically adding pulses of negative and positive current to the analog signal to provide current balancing for integration of the analog signal, where the addition of the positive and negative current is controlled by the size of the first and second pulse widths.