In metal-oxide-semiconductor (MOS) image sensors that are capable of having a mix of peripheral circuits on a single chip, and especially in image sensors with a high number of pixels, a column analog-to-digital (A/D) conversion method is commonplace that simultaneously A/D converts a pixel output signal per pixel row.
In recent years, with the further advancement of frame rates and digital output data bitrates in solid-state imaging devices, A/D convertor circuits are being proposed that have a configuration in which different A/D conversion methods are used for high-order bits and low-order bits in order to perform a high-speed and high-resolution A/D conversion.
To give an example, Patent Literature (PTL) 1 discloses a column A/D convertor circuit that digitally converts high-order bits using a successive approximation A/D conversion method and digitally converts low-order bits using a single slope A/D conversion method.
USPTO Backgrounds
USPTO Backgrounds