Image sensing device
An image sensing device for obtaining an image of a scene by sensing light is disclosed. The image sensing device includes a pixel circuit configured to output a pixel signal based on a voltage level of a floating diffusion node at which charges generated corresponding to an intensity of incident light are accumulated, a voltage controller configured to control a voltage level of an output node where the pixel signal is output in response to a voltage control signal, a conversion circuit configured to convert the pixel signal into a digital signal, and a voltage trimming circuit configured to control the voltage control signal based on the digital signal.
1 . An image sensing device comprising:
a pixel circuit configured to output a pixel signal based on a voltage level of a floating diffusion node at which charges generated corresponding to an intensity of incident light are accumulated;
a voltage controller configured to control a voltage level of an output node where the pixel signal is output in response to a voltage control signal and an inverted selection control signal;
a conversion circuit configured to convert the pixel signal into a digital signal; and
a voltage trimming circuit configured to control the voltage control signal based on the digital signal.
2 . The image sensing device according to claim 1 , wherein the pixel circuit includes a selection transistor configured to output the pixel signal corresponding to the voltage level of the floating diffusion node in response to a selection control signal.
3 . The image sensing device according to claim 2 , wherein the pixel circuit further includes:
a source follower transistor configured to output a signal corresponding to the voltage level of the floating diffusion node to the selection transistor;
a photoelectric conversion element configured to generate the charges corresponding to the intensity of incident light;
a transfer transistor configured to transfer the charges generated by the photoelectric conversion element to the floating diffusion node in response to a transfer signal; and
a reset transistor configured to reset the voltage level of the floating diffusion node in response to a pixel reset signal.
4 . The image sensing device according to claim 2 , wherein the voltage controller includes:
a voltage control transistor connected between a power-supply voltage terminal and a first node and configured to receive the voltage control signal through a gate terminal thereof; and
an inversion transistor connected between the first node and the output node and configured to receive the inverted selection control signal through a gate terminal thereof, wherein the inverted selection control signal is opposite in phase to the selection control signal.
5 . The image sensing device according to claim 4 , wherein, during a time section where the selection transistor is turned off and the voltage level of the floating diffusion node is changed, the inversion transistor is turned on and a voltage level of the pixel signal is determined based on a voltage level of the voltage control signal.
6 . The image sensing device according to claim 2 , wherein:
when the selection transistor is turned off, a voltage level of the pixel signal is controlled in response to the voltage control signal; and
when the selection transistor is turned on, the voltage level of the pixel signal is controlled in response to the voltage level of the floating diffusion node.
7 . The image sensing device according to claim 2 , wherein the pixel circuit includes:
a source follower transistor configured to output a signal corresponding to the voltage level of the floating diffusion node to the selection transistor;
a photoelectric conversion element configured to generate the charges corresponding to the intensity of incident light;
a transfer transistor configured to transfer the charges generated by the photoelectric conversion element to the floating diffusion node in response to a transfer signal;
a reset transistor configured to reset the voltage level of the floating diffusion node in response to a pixel reset signal; and
a conversion gain control element configured to selectively supply a ground voltage to the floating diffusion node in response to a conversion gain control signal.
8 . The image sensing device according to claim 7 , wherein the conversion gain control element includes a transistor connected between the floating diffusion node and a ground voltage terminal and configured to receive a conversion gain control signal through a gate terminal thereof.
9 . The image sensing device according to claim 1 , wherein the voltage trimming circuit is configured to:
adjust a voltage level of the voltage control signal to a first level when a digital code value of the digital signal is a first value; and
adjust a voltage level of the voltage control signal to a second level higher than the first level when the digital code value of the digital signal is a second value greater than the first value.
10 . The image sensing device according to claim 1 , further comprising a pixel biasing circuit connected between the output node and a ground voltage terminal and configured to be driven based on a bias voltage.
11 . An image sensing device comprising:
a floating diffusion node configured to accumulate charges generated corresponding to an intensity of incident light;
a selection transistor configured to output a pixel signal corresponding to a voltage level of the floating diffusion node to an output node in response to a selection control signal;
a voltage control transistor connected between a power-supply voltage terminal and a first node and configured to receive a voltage control signal through a gate terminal thereof;
an inversion transistor connected between the first node and the output node and configured to receive an inverted selection control signal through a gate terminal thereof;
a conversion circuit configured to convert the pixel signal into a digital signal; and
a voltage trimming circuit configured to control the voltage control signal based on the digital signal.
12 . The image sensing device according to claim 11 , further comprising:
a source follower transistor configured to output a signal corresponding to the voltage level of the floating diffusion node to the selection transistor;
a photoelectric conversion element configured to generate the charges corresponding to the intensity of incident light;
a transfer transistor configured to transfer the charges generated by the photoelectric conversion element to the floating diffusion node in response to a transfer signal; and
a reset transistor configured to reset the voltage level of the floating diffusion node in response to a pixel reset signal.
13 . The image sensing device according to claim 12 , further comprising a conversion gain control element configured to selectively supply a ground voltage to the floating diffusion node in response to a conversion gain control signal.
14 . The image sensing device according to claim 13 , wherein, when the conversion gain control element is turned off and the inversion transistor is turned on, a voltage level of the output node is determined by the voltage control signal.
15 . The image sensing device according to claim 11 , wherein the inverted selection control signal is opposite in phase to the selection control signal.
16 . The image sensing device according to claim 11 , wherein, during a time section where the selection transistor is turned off and the voltage level of the floating diffusion node is changed, the inversion transistor is turned on and a voltage level of the pixel signal is determined based on a voltage level of the voltage control signal.
17 . The image sensing device according to claim 11 , wherein:
when the selection transistor is turned off, a voltage level of the pixel signal is controlled in response to the voltage control signal; and
when the selection transistor is turned on, a voltage level of the pixel signal is controlled in response to the voltage level of the floating diffusion node.
18 . The image sensing device according to claim 11 , wherein the voltage trimming circuit is configured to:
adjust a voltage level of the voltage control signal to a first level when a digital code value of the digital signal is a first value; and
adjust a voltage level of the voltage control signal to a second level higher than the first level when the digital code value of the digital signal is a second value greater than the first value.
19 . The image sensing device according to claim 11 , further comprising:
a pixel biasing circuit connected between the output node and a ground voltage terminal and configured to be driven based on a bias voltage.
20 . An image sensing device comprising:
a pixel array including a plurality of pixels and configured to generate a pixel signal;
a row driver configured to drive the plurality of pixels;
a conversion circuit configured to generate a digital signal based on a ramp signal and the pixel signal; and
a voltage trimming circuit configured to trim, based on the digital signal, a voltage level of a control signal for controlling a voltage level of an output node through which the pixel signal is output,
wherein the voltage trimming circuit is configured to adjust the voltage level of the control signal to a first level when a digital code value of the digital signal is a first value, and adjust the voltage level of the control signal to a second level higher than the first level when the digital code value of the digital signal is a second value greater than the first value.