A CMOS image sensor includes an image pixel array, a dark pixel array, data bit liens, reference bit lines, a driver, comparators, and analog-to-digital converter (“ADC”) circuits. The image pixel array generates analog image signals in response to incident light. The dark pixel array generates analog black reference signals for analog black level calibration of the analog image signals. In one embodiment, the data bit lines each coupled to a different column of image pixels of the image pixel array and the reference bit lines each coupled to a different column of black reference pixels within the dark pixel array. The driver is coupled to the reference bit lines to drive an analog black reference signal. The comparators each couple to one of the data bit lines and each coupled to an output of the driver and offset the analog image signals with the analog black reference signals in an analog domain. The ADC circuits each coupled to an output of a comparator.