Cmos image sensor and auto exposure method performed in units of pixels in the same

A complementary metal oxide (CMOS) image sensor (CIS) comprising:

• an upper chip comprising a plurality of pixels each including a photodiode, the pixels arranged in a two-dimensional (2D) array;
• and
• at least one lower chip comprising a plurality of analog-digital converters (ADCs) and signal processing circuits, wherein the plurality of ADCs perform auto exposure in units of the pixels and the signal processing circuits process pixel signals from the pixels,
• wherein the upper chip is stacked on the at least one lower chip, and the pixels and the ADCs are connected in a one-to-one correspondence to each other.

A method of performing auto exposure (AE) in units of pixels in a complementary metal oxide (CMOS) image sensor (CIS) comprising the pixels each including a photodiode, the CIS further comprising a plurality of analog-to-digital converters (ADCs) connected in one-to-one correspondence to the pixels, the method comprising:

• resetting floating diffusion (FD) regions of the pixels and performing analog-to-digital (AD) conversions on reset signals of reset transistors of the pixels by the plurality of ADCs;
• transferring charges accumulated in the photodiodes to the FD regions by turning on transfer transistors of the pixels and thereafter performing AD conversion on pixel signals of the pixels and starting an exposure in a current-frame period;
• and
• performing an auto exposure (AE) on the plurality of pixels by the plurality of ADCs during the exposure in the current-frame period.