An image sensor includes a pixel array disposed in a first semiconductor die. The pixel array is partitioned into a plurality of pixel sub-arrays. Each one of the plurality of pixel sub-arrays is arranged into a plurality of pixel groups. Each one of the plurality of pixel groups is arranged into a p×q array of pixel cells. A plurality of readout circuits is disposed in a second semiconductor die. An interconnect layer is stacked between the first semiconductor die and the second semiconductor die. The interconnect layer includes a plurality of conductors. Each one of the plurality of pixel sub-arrays is coupled to a corresponding one of the plurality of readout circuits through a corresponding one of the plurality of conductors.