Patent ID: 8669511

Claim:
A device for determination of a charge amount of a capacitive element, comprising: a plurality of pixel cells arranged in columns and rows, each pixel cell including an output, wherein pixel cells arranged in a column have their respective outputs connected to a column line configured to form the capacitive element; a voltage comparator device configured to compare a voltage on the capacitive element to a reference voltage, and to determine whether the voltage on the capacitive element is greater than the reference voltage, thereby corresponding to a first sign, or the voltage on the capacitive element is smaller than the reference voltage, thereby corresponding to a second sign; a control circuit including: a pulsed current source, configured to output charge packets of a specified current intensity and duration, or a charge pump; wherein the device is configured to feed charge packets to the capacitive element, and remove charge packets from the capacitive element, in cycles, so that the difference between the voltage on the capacitive element and the reference voltage becomes smaller, by causing, in one cycle, one of the feed and the removal of one or more charge packets of a first charge amount, until a change between the signs is detected by the voltage comparator, and then, in a next cycle, causing the other one of the feed and the removal of one or more charge packets of a second charge amount smaller than the first charge amount, until a change between the signs is detected by the voltage comparator; an evaluator configured to inference a digital value indicative of the charge on the capacitive element, based on a count of the charge packets and the charge amount of the charge packets fed to and/or removed from the capacitive element.