A system and method is provided for analog to digital conversion, the system having: a front end whereby a current is converted to digital pulses; and a back end with a coarse conversion unit outputting a pulse count; and a fine conversion unit outputting a count time measurement count; wherein said back end unit is configured to combine said pulse count and said count time measurement to produce a high dynamic range output, said output being the product of the one more than the pulse count and the integration time divided by the sum of the integration time and the count time management count.