SEMICONDUCTOR DEVICE

摘要

A problem in conventional semiconductor devices is that a frame rate for acquiring images cannot be increased. A semiconductor device according to one embodiment sets a slope of a ramp signal provided to an analog-to-digital converter for converting pixel signals into digital values such that it becomes large in a conversion process corresponding to short-time exposure whereas it becomes small in a conversion process corresponding to long-time exposure, sets a sweep time of the ramp signal such that it becomes short in the conversion process corresponding to the short-time exposure, whereas it becomes long in the conversion process corresponding to the long-time exposure, and generates two pieces of data such that the number of bits in a digital value corresponding to the short-time exposure will become smaller than the number of bits in the digital value corresponding to the long-time exposure.

主权项

1. A semiconductor device comprising:
a pixel area that accumulates charge according to an amount of incident light and outputs pixel signals; an analog-to-digital converter that reads the pixel signals and outputs digital values each according to magnitude of a corresponding one of the pixel signals using a ramp signal; a control signal generating circuit that outputs an exposure time switching pulse and a sweep period pulse, the exposure time switching pulse indicating a length of an exposure time in which light-receiving elements arranged in the pixel area receive the incident light, and the sweep period pulse specifying a time in which a ramp signal generating circuit sweeps the ramp signal; a ramp waveform control circuit that stores a short-time exposure slope setting value and a long-time exposure slope setting value, switches between the short-time exposure slope setting value and the long-time exposure slope setting value according to the exposure time switching pulse, and outputs the switched one of the short-time exposure slope setting value and the long-time exposure slope setting value, the short-time exposure slope setting value setting a slope of the ramp signal used when the exposure time switching pulse indicates a short-time exposure period, and the long-time exposure slope setting value being a setting value for the slope of the ramp signal used when the exposure time switching pulse indicates a long-time exposure period, and the long-time exposure slope setting value indicating a slope gentler than that indicated by the short-time exposure gradient setting value; a ramp waveform generating circuit that outputs a ramp signal having a slope in accordance with the slope setting value output by the ramp waveform control circuit, wherein the control signal generating circuit sets a sweep time specified by the sweep period pulse output in a period indicated by the exposure time switching pulse as being the short-time exposure period in such a way that it will be shorter than a sweep period specified by the sweep period pulse output in a period indicated by the exposure time switching pulse as being the long-time exposure period, and the analog-to-digital converter generates a first digital value corresponding to the short-time exposure period and a second digital value corresponding to the long-time exposure period.