Fuente: Wipo "digitalization" An analog to digital converter (ADC) that is configured to service a photo-diode includes a capacitor and a self-referenced latched comparator. The capacitor produces a photo-diode voltage based on charging by a photo-diode current associated with the photo-diode and a digital to analog converter (DAC) source current and/or a DAC sink current. The self-referenced latched comparator generates a first digital signal that is based on a difference between the photo-diode voltage and a threshold voltage associated with the self-referenced latched comparator. Also, one or more processing modules executes operational instructions to process the first digital signal to generate a second digital signal and/or a third digital signal. An N-bit DAC generates the DAC source current based on the second digital signal, and an M-bit DAC generates the DAC sink current based on the third digital signal. The DAC source current and/or the DAC sink current tracks the photo-diode current.