Ramp-signal generator circuit, and image sensor and imaging system including the same

摘要

The ramp-signal generator circuit includes a reference voltage generator that changes the voltage of a reference signal Vr to a comparator setting voltage VR for compensating for a voltage difference between a reference signal Vr and an analog input signal (Vs1-Vsn) before comparison by an analog-to-digital converter circuit and outputs a ramp signal whose slope starts from the comparator setting voltage VR in response to a start of the comparison. The ramp-signal generator circuit is configured to add a predetermined enhanced voltage VA to the comparator setting voltage VR before the comparison.

主权项

1. A ramp-signal generator circuit that outputs, to a single-slope analog-to-digital converter circuit, a ramp signal that is sloped in terms of time with a predetermined inclination, as a reference signal, wherein
the analog-to-digital converter circuit includes a comparator having first and second input terminals and configured to receive the reference signal at the first input terminal and to receive an analog input signal at the second input terminal, the analog-to-digital converter circuit converts the analog input signal into a digital signal based on a result of comparison by the comparator, the ramp-signal generator circuit includes a reference voltage generator configured to change a voltage of the reference signal to a comparator setting voltage for compensating for a voltage difference between the first and second input terminals of the comparator before the comparison, and configured to output the ramp signal whose slope starts from the comparator setting voltage in response to a start of the comparison, and the ramp-signal generator circuit is configured to add a predetermined enhanced voltage to the comparator setting voltage before the comparison.