Image sensor, imaging device having the image sensor, and operating method thereof

1. An image sensor, comprising:

a first sampling capacitor corresponding to first illumination connected to a power supply terminal;

a second sampling capacitor corresponding to second illumination connected to the power supply terminal;

a third sampling capacitor connected between a first sampling node and a second sampling node;

a first transistor connected between a photodiode and a floating diffusion node and configured to be controlled by a transfer gate signal;

a second transistor connected between the power supply terminal and an expansion node and configured to be controlled by a reset gate signal;

a third transistor connected between the expansion node and the floating diffusion node and configured to be controlled by a conversion gain gate signal;

a fourth transistor having a drain connected to the power supply terminal, a source connected to a sampling node, and a gate connected to the floating diffusion node;

a fifth transistor connected between the sampling node and a ground terminal and configured to be controlled by a pass signal;

a sixth transistor connected between the sampling node and the first sampling node and configured to be controlled by a sampling signal;

a seventh transistor connected between the first sampling capacitor and the first sampling node and configured to be controlled by a first switch signal;

an eighth transistor connected between the second sampling capacitor and the first sampling node and configured to be controlled by a second switch signal;

a ninth transistor connected between the power supply terminal and the second sampling node and configured to be controlled by an operating signal;

a tenth transistor having a drain connected to the power supply terminal and a gate connected to the second sampling node; and

an eleventh transistor connected between a source of the tenth transistor and a corresponding column line and configured to be controlled by a selection signal.

2. The image sensor of claim 1 , further comprising an expansion capacitor connected between the expansion node and the ground terminal.

3. The image sensor of claim 2 , further comprising a secondary photodiode connected between the expansion node and the ground terminal.

4. The image sensor of claim 1 , further comprising an expansion capacitor connected between the expansion node and the power supply terminal.

5. The image sensor of claim 1 , wherein based on the conversion gain gate signal being at a high level, charges overflowed from the photodiode are stored in the first sampling capacitor.

6. The image sensor of claim 5 , wherein after the overflowed charges are stored in the first sampling capacitor for the first illumination, based on the conversion gain gate signal being at a low level, and the transfer gate signal being at the high level for a predetermined time, charges corresponding to the second illumination are stored in the floating diffusion node.

7. The image sensor of claim 6 , wherein based on the transfer gate signal being at the low level, and the second switch signal being at the high level, a second sampling operation for storing the charges corresponding to the second illumination in the second sampling capacitor is performed.

8. The image sensor of claim 7 , wherein after the second sampling operation is performed, based on the conversion gain gate signal being at the low level, and the transfer gate signal being at the high level for the predetermined time, charges corresponding to the first illumination are stored in the floating diffusion node.

9. The image sensor of claim 8 , wherein based on the transfer gate signal being at the low level and the first switch signal being at the high level, a first sampling operation for storing the charges corresponding to the first illumination in the first sampling capacitor is performed.

10. The image sensor of claim 1 , wherein the first illumination is higher than the second illumination.

11. An imaging device, comprising:

at least one pixel array having a plurality of pixels connected between a plurality of row lines and a plurality of column lines;

a row driver configured to select row lines from among the plurality of row lines;

a read-out circuit configured to receive analog pixel signals from column lines from among the plurality of column lines corresponding to pixels from among the plurality of pixels connected to the selected row lines, and to convert the received analog pixel signals into digital signals;

a column driver configured to output image data corresponding to the column lines based on the digital signals;

a timing controller configured to control an operation timing of the at least one pixel array, the row driver, the read-out circuit, and the column driver; and

an image signal processor configured to process the image data output from the column driver,

wherein each of the plurality of pixels is configured to perform a first sampling operation corresponding to first illumination and a second sampling operation corresponding to second illumination lower than the first illumination,

wherein the each of the plurality of pixels comprises a plurality of sampling capacitors connected to a power supply terminal, a plurality of transistors connected between the plurality of sampling capacitors and a first sampling node, an additional sampling capacitor connected between the first sampling node and a second sampling node, a first additional transistor having a drain connected to the power supply terminal, a source connected to an additional sampling node, and a gate connected to a floating diffusion node, and a second additional transistor connected between the additional sampling node and a ground terminal and configured to be controlled by a pass signal.

12. The imaging device of claim 11 , wherein the each of the plurality of pixels is configured to perform a conversion gain variation operation.

13. The imaging device of claim 11 , wherein the each of the plurality of pixels includes at least two photodiodes.

14. The imaging device of claim 11 , wherein the each of the plurality of pixels comprises:

a first sampling capacitor from among the plurality of sampling capacitors, wherein the first sampling capacitor corresponds to the first illumination and is connected to the power supply terminal;

a second sampling capacitor from among the plurality of sampling capacitors, wherein the second sampling capacitor corresponds to the second illumination and is connected to the power supply terminal;

a first transistor connected between a photodiode and the floating diffusion node and configured to be controlled by a transfer gate signal;

a second transistor connected between the power supply terminal and an expansion node and configured to be controlled by a reset gate signal;

a third transistor connected between the expansion node and the floating diffusion node and configured to be controlled by a conversion gain gate signal;

a sixth transistor connected between the additional sampling node and the first sampling node and configured to be controlled by a sampling signal;

a seventh transistor from among the plurality of transistors, wherein the seventh transistor is connected between the first sampling capacitor and the first sampling node and is configured to be controlled by a first switch signal;

an eighth transistor from among the plurality of transistors, wherein the eighth transistor is connected between the second sampling capacitor and the first sampling node and is configured to be controlled by a second switch signal;

a ninth transistor connected between the power supply terminal and the second sampling node and configured to be controlled by an operating signal;

a tenth transistor having a drain connected to the power supply terminal and a gate connected to the second sampling node; and

an eleventh transistor connected between a source of the tenth transistor and a corresponding column line and configured to be controlled by a selection signal.

15. The imaging device of claim 14 , further comprising:

an expansion capacitor connected between the expansion node and the ground terminal; and

a secondary photodiode connected between the expansion node and the ground terminal.

16. An operating method of an image sensor, the operating method comprising:

performing a first sampling operation corresponding to first illumination in at least one pixel, wherein each pixel of the at least one pixel comprises a plurality of sampling capacitors connected to a power supply terminal, a plurality of sampling transistors connected between the plurality of sampling capacitors and a first sampling node, an additional sampling capacitor connected between the first sampling node and a second sampling node, a first additional transistor having a drain connected to a power supply terminal, a source connected to an additional sampling node, and a gate connected to a floating diffusion node, and a second additional transistor connected between the additional sampling node and a ground terminal and configured to be controlled by a pass signal;

performing a second sampling operation corresponding to second illumination in the at least one pixel; and

outputting a first pixel voltage corresponding to the first sampling operation, or outputting a second pixel voltage corresponding to the second sampling operation, in the at least one pixel.

17. The operating method of the image sensor of claim 16 , wherein the at least one pixel is configured to perform dual-conversion gain.

18. The operating method of the image sensor of claim 16 , further comprising performing light-emitting diode (LED) flicker mitigation using a secondary photodiode in the at least one pixel.

19. The operating method of the image sensor of claim 16 , further comprising storing overflowed charges corresponding to the first illumination in a capacitor of the plurality of sampling capacitors.