Photoelectric conversion device and imaging system
An embodiment includes: a semiconductor substrate including a pixel well region and a peripheral well region; a pixel ground line arranged above the pixel well region; a pixel well contact between the pixel ground line and the pixel well region; pixels arranged to form columns in the pixel well region; a reference signal generation circuit arranged in the peripheral well region; and comparator units arranged in the peripheral well region, provided to respective columns, and each configured to receive the pixel signal from the pixels on a corresponding column and the reference signal. Each comparator unit includes a comparator having a first input node that receives the pixel signal and a second input node that receives the reference signal, a first capacitor unit between the reference signal generation circuit and the second input node, and a second capacitor unit between the second input node and the pixel ground line.
1. A photoelectric conversion device comprising:
a semiconductor substrate including a pixel well region well;
a pixel ground line arranged above the pixel well region;
a pixel well contact connected between the pixel ground line and the pixel well region;
a plurality of pixels arranged to form a plurality of columns in the pixel well region and each configured to output a pixel signal in accordance with a light amount of incident light;
a reference signal generation circuit configured to generate a reference signal having a predetermined amplitude; and
a plurality of comparator units provided to corresponding ones of the plurality of columns, and each configured to receive the pixel signal from the pixels on a corresponding column and the reference signal,
wherein each of the plurality of comparator units includes
a comparator having a first input node that receives the pixel signal and a second input node that receives the reference signal,
a first capacitor unit connected between the reference signal generation circuit and the second input node, and
a second capacitor unit connected between the second input node and the pixel ground line.
2. The photoelectric conversion device according to claim 1 further comprising a peripheral well region included in the semiconductor substrate,
wherein the pixel ground line extends above the peripheral well region and is connected to the second capacitor unit in a region overlapping the peripheral well region.
3. The photoelectric conversion device according to claim 1 , wherein the second capacitor unit includes at least one series-connected component of a first capacitor element and a first switch.
4. The photoelectric conversion device according to claim 3 , wherein the second capacitor unit includes a plurality of series-connected components of the first capacitor element and the first switch in parallel.
5. The photoelectric conversion device according to claim 3 further comprising a control circuit that switches an amplitude of the reference signal input to the second input node by controlling a connection state of the first switch.
6. The photoelectric conversion device according to claim 1 further comprising a plurality of output lines each arranged on corresponding ones of the plurality of columns, wherein the pixel signal from the pixels on a corresponding column is output to each of the plurality of output lines,
wherein each of the plurality of comparator units further includes a third capacitor unit connected between each of the output lines on a corresponding column and the first input node.
7. The photoelectric conversion device according to claim 6 , wherein each of the plurality of comparator units further includes a sample-hold unit provided between each of the output lines on the corresponding column and the third capacitor unit.
8. The photoelectric conversion device according to claim 7 , wherein the sample-hold unit includes a second switch connected between the output lines on the corresponding column and the third capacitor unit and a fourth capacitor unit connected between the pixel ground line and a connection node between the second switch and the third capacitor unit.
9. The photoelectric conversion device according to claim 8 , wherein the fourth capacitor unit includes a series-connected component between a second capacitor element and a third switch.
10. The photoelectric conversion device according to claim 1 , wherein a ground terminal of the reference signal generation circuit is connected to the pixel ground line.
11. The photoelectric conversion device according to claim 1 , wherein the pixel ground line extends in a direction along the plurality of columns.
12. The photoelectric conversion device according to claim 1 , wherein the pixel ground line is provided to corresponding ones of the plurality of columns.
13. The photoelectric conversion device according to claim 1 , wherein the reference signal is a ramp signal whose signal level changes with a lapse of time.
14. The photoelectric conversion device according to claim 1 further comprising:
a peripheral ground line arranged above a peripheral well region included in the semiconductor substrate; and
a pixel well contact connected between the peripheral ground line and the peripheral well region.
15. The photoelectric conversion device according to claim 1 further comprising:
a counter circuit that starts a count operation in synchronization with output of the reference signal from the reference signal generation circuit; and
a storage unit provided to each of the plurality of columns and configured to store, as digital data of the pixel signal, a count value indicated by a count signal output from the counter circuit in accordance with a result of comparison between the pixel signal and the reference signal performed by the comparator unit.
16. A photoelectric conversion device comprising:
a semiconductor substrate including a pixel well region;
a pixel ground line arranged above the pixel well region;
a pixel well contact connected between the pixel ground line and the pixel well region;
a plurality of pixels arranged to form a plurality of columns in the pixel well region and each configured to output a pixel signal;
a reference signal generation circuit configured to generate a reference signal; and
a plurality of readout circuits provided to corresponding ones of the plurality of columns, and each configured to receive the pixel signal from the pixels on a corresponding column and the reference signal,
wherein each of the plurality of readout circuits includes
a differential amplifier circuit having a first input node that receives the pixel signal and a second input node,
a first capacitor unit connected between the reference signal generation circuit and the second input node, and
a second capacitor unit connected between the second input node and the pixel ground line.
17. An imaging system comprising:
the photoelectric conversion device according to claim 1 ; and
a signal processing unit that processes a signal output from the photoelectric conversion device.
18. An imaging system comprising:
the photoelectric conversion device according to claim 16 ; and
a signal processing unit that processes a signal output from the photoelectric conversion device.
19. A movable object comprising:
the photoelectric conversion device according to claim 1 ;
a distance information acquisition unit that acquires distance information on a distance to an object, from a parallax image based on signals from the photoelectric conversion device; and
a control unit that controls the movable object based on the distance information.
20. A movable object comprising:
the photoelectric conversion device according to claim 16 ;
a distance information acquisition unit that acquires distance information on a distance to an object, from a parallax image based on signals from the photoelectric conversion device; and
a control unit that controls the movable object based on the distance information.