ADC can be performed off-chip when there is not much demand on system integration. However, when system level integration is important, for example in digital active pixel sensors, on-chip ADC becomes necessary. In addition to the type of ADC the number of ADC circuits that can be implemented on the chip can also be selected based on demand. However, a single ADC will avoid the addition of fixed pattern noise, which can be introduced by multiple ADCs. On the other hand, the less speed demanding feature of multiple ADCs may be considered as an advantage.
Vision chips consist of one or two dimensional arrays of cells.
The output a vision chip may or may not be visualized during its operation. In the most intuitive method outputs can be scanned, digitized and visualized on the monitor of a computer. This is particularly important for testing prototype vision chips. For more precise characterization one needs to use data acquisition techniques.