Image sensing device and electronic device comprising the same
An image sensing device includes a pixel circuit, a readout circuit, and a row driver. The pixel circuit is configured to output a pixel signal in response to a selection signal. The readout circuit is configured to output a digital signal corresponding to the pixel signal, generate a gain control signal based on a first pixel signal received from the pixel circuit, provide the gain control signal to the pixel circuit, receive a second pixel signal output by the pixel circuit using the gain control signal, and output a digital signal corresponding to the second pixel signal. The row driver is configured to provide the selection signal to the pixel circuit while maintaining the selection signal at a first level while the readout circuit provides the gain control signal to the pixel circuit and the pixel circuit outputs the second pixel signal to the readout circuit.
1. An image sensing device comprising:
a pixel circuit including a floating diffusion, a photoelectric element, a drive transistor, a DCG (Dual Conversion Gain) transistor, a selection transistor, a column line connected to the selection transistor,
the floating diffusion being a region of the pixel circuit,
the floating diffusion being configured to store an electric charge generated by the photoelectric element,
the drive transistor being configured to generate a pixel signal based on the electric charge stored in the floating diffusion,
the selection transistor being configured to output the pixel signal generated by the drive transistor to the column line in response to the selection transistor receiving a selection signal,
the selection transistor being configured to output a first pixel signal to the column line based on the electric charge stored in the floating diffusion in a state in which the DCG transistor is turned off,
the DCG transistor being configured to change a capacitance of the floating diffusion in response to the DCG transistor receiving a gain control signal, and
the pixel circuit being configured to perform an operation of the selection transistor outputting the first pixel signal to the column line and the DCG transistor receiving the gain control signal while the selection transistor receives the selection signal maintained at a first level; and
processing circuitry configured to determine the gain control signal using a result of a comparison between the first pixel signal and a ramp signal during one sensing cycle.
2. The image sensing device of claim 1 , wherein
the pixel circuit further includes a reset transistor and a capacitor,
the reset transistor is configured to provide a reset voltage to the floating diffusion in response to a reset signal,
the capacitor connected between the reset transistor and the DCG transistor, and
the DCG transistor is configured to change the capacitance of the floating diffusion using the capacitor.
3. The image sensing device of claim 2 , wherein a capacitance of the capacitor is greater than the capacitance of the floating diffusion.
4. The image sensing device of claim 2 , wherein the reset transistor and the DCG transistor are configured to be simultaneously turned on in response the reset signal.
5. The image sensing device of claim 1 , wherein
the pixel circuit further includes an electric charge transfer transistor configured to provide electric charge generated by the photoelectric element to the floating diffusion in response to a transmission signal,
the photoelectric element includes a first photoelectric element, a second photoelectric element, a third photoelectric element, and a fourth photoelectric element separated from each other, and
the electric charge transfer transistor includes a first charge transfer transistor, a second charge transfer transistor, a third charge transfer transistor, and a fourth charge transfer transistor,
the first charge transfer transistor is connected to the first photoelectric element and the floating diffusion,
the second charge transfer transistor is connected to the second photoelectric element and the floating diffusion,
the third charge transfer transistor is connected to the third photoelectric element and the floating diffusion, and
the fourth charge transfer transistor is connected to the fourth photoelectric element and the floating diffusion.
6. An image sensing device comprising:
a pixel circuit including a floating diffusion, a photoelectric element, a drive transistor, a DCG (Dual Conversion Gain) transistor, a selection transistor, a column line connected to the selection transistor,
the floating diffusion being a region of the pixel circuit,
the floating diffusion being configured to store an electric charge generated by the photoelectric element,
the drive transistor being configured to generate a pixel signal based on the electric charge stored in the floating diffusion,
the selection transistor being configured to output the pixel signal generated by the drive transistor to the column line in response to the selection transistor receiving a selection signal,
the selection transistor being configured to output a first pixel signal to the column line based on the electric charge stored in the floating diffusion in a state in which the DCG transistor is turned off,
the DCG transistor being configured to change a capacitance of the floating diffusion in response to the DCG transistor receiving a gain control signal, and
the pixel circuit being configured to perform an operation of the selection transistor outputting the first pixel signal to the column line and the DCG transistor receiving, the gain control signal while the selection transistor receives the selection signal maintained at a first level, wherein
the pixel circuit further includes a reset transistor and a capacitor,
the reset transistor is configured to provide a reset voltage to the floating diffusion in response to a reset signal,
the capacitor is connected between the reset transistor and the DCG transistor,
the DCG transistor is configured to change the capacitance of the floating diffusion using the capacitor,
the pixel circuit further includes an OR gate, and
the OR gate is configured to receive the gain control signal and the reset signal, perform an OR calculation based on the gain control signal and the reset signal, and provide a result of the OR calculation to the DCG transistor.
7. An image sensing device comprising:
a pixel circuit configured to output a pixel signal in response to a selection signal; and
a readout circuit configured to output a digital signal corresponding to the pixel signal provided from the pixel circuit,
the readout circuit being configured to receive a first pixel signal from the pixel circuit, generate a gain control signal based on the first pixel signal, and provide the gain control signal to the pixel circuit,
the readout circuit being configured to receive a second pixel signal output by the pixel circuit using the gain control signal, and output a digital signal corresponding to the second pixel signal, and
a row driver configured to provide the selection signal to the pixel circuit while maintaining the selection signal at a first level during an operation in which the readout circuit provides the gain control signal to the pixel circuit and an operation in which the pixel circuit outputs the second pixel signal to the readout circuit are performed.
8. The image sensing device of claim 7 , wherein
the readout circuit includes a comparator and a control signal generator,
the comparator is configured to output a comparison signal based on a comparison of a ramp signal with the first pixel signal,
the control signal generator is configured to generate the gain control signal based on the comparison signal.
9. The image sensing device of claim 8 , wherein
the readout circuit further includes a timing controller,
the timing controller is configured to receive a first gain control signal generated by the control signal generator, and
the timing controller is configured to provide the pixel circuit with a second gain control signal generated by adjusting a timing of the first gain control signal.
10. The image sensing device of claim 9 , wherein
the timing controller includes a storage unit, a first switch, and a second switch,
the storage unit is configured to store the first gain control signal by turning on the first switch to provide a stored first gain control signal, and
the timing controller is configured output the stored first gain control signal as the second gain control signal by turning on the second switch.
11. The image sensing device of claim 7 , wherein
the readout circuit is configured to output the digital signal corresponding to the second pixel signal and the digital signal includes conversion gain information corresponding to the gain control signal generated the first pixel signal.
12. The image sensing device of claim 11 , further comprising:
a pixel array including a plurality of pixels, wherein
the plurality of pixels includes a first pixel and a second pixel,
the first pixel is configured to output a third pixel signal,
the second pixel is configured to output a fourth pixel signal,
the third pixel signal and the fourth pixel signal constitute an image of same frame,
the readout circuit is configured to output a first digital signal corresponding to the third pixel signal and output a second digital signal corresponding to the fourth pixel signal, and
the first digital signal and the second digital signal include different types of conversion gain information from each other.
13. The image sensing device of claim 7 , further comprising:
a pixel array including a plurality of pixels, wherein
each pixel of the pixel array includes the pixel circuit and the readout circuit.