A light-emitting chip mounted on a long circuit board, the light-emitting chip comprising:
- a plurality of light-emitting portions arranged along a longitudinal direction of the circuit board, the plurality of light-emitting portions emitting light for exposing a photosensitive member;
- a first electrical pad configured to receive image data for controlling the plurality of light-emitting portions on and off;
- a second electrical pad configured to receive the image data;
- and
- a drive circuit including:
- a plurality of image-data transferring units provided so as to correspond one-to-one with the plurality of light-emitting portions and each outputting, based on the image data, a drive signal for controlling drive of a corresponding one of the plurality of light-emitting portions, the plurality of image-data transferring units including:
- a first image-data transferring unit configured to output the drive signal to a first light-emitting portion;
- a second image-data transferring unit configured to output the drive signal to a second light-emitting portion that is adjacent to the first light-emitting portion on one side in the longitudinal direction of the circuit board;
- a third image-data transferring unit configured to output the drive signal to a third light-emitting portion that is adjacent to the second light-emitting portion on the one side in the longitudinal direction of the circuit board, and output, to one of the first and second image-data transferring units, a start signal that is an instruction to start outputting the drive signal;
- and
- a fourth image-data transferring unit configured to output the drive signal to a fourth light-emitting portion that is adjacent to the third light-emitting portion on the one side in the longitudinal direction of the circuit board, and output, to one of the second and third image-data transferring units, a start signal that is an instruction to start outputting the drive signal;
- a first signal line connected to the first and third image-data transferring units, the first signal line configured to transmit the image data received via the first electrical pad;
- a second signal line configured to transmit the image data received via the second electrical pad;
- a first switch circuit configured to switch between a first state in which the start signal output by the fourth image-data transferring unit is output to the second image-data transferring unit and the start signal output by the third image-data transferring unit is output to the first image-data transferring unit, and a second state in which the start signal output by the fourth image-data transferring unit is output to the third image-data transferring unit and the start signal output by the third image-data transferring unit is output to the second image-data transferring unit;
- and
- a second switch circuit configured to switch between a third state in which the first and third image-data transferring units and the first signal line are connected, and the first and third image-data transferring units and the second signal line are not connected, and a fourth state in which the first and third image-data transferring units and the second signal line are connected, and the first and third image-data transferring units and the first signal line are not connected.