The present disclosure relates to a method and apparatus to perform a low power activation of a system. In one embodiment, the apparatus includes a sensor element configured to output a sensor output signal corresponding to a sensed quantity to a digital difference detection circuit. The digital difference detection circuit has a digital measurement element configured to track the sensor output signal and generate a digital signal therefrom, a digital storage element configured to store previous digital signals corresponding to the sensor output signal generated over time, and a difference detector configured to detect a difference between a current digital signal and at least one of the previous digital signals. If the difference is larger than a digital reference level, the difference detector causes an activation signal generator to generate an activation signal that awakens a system from a sleep mode or a low-power mode.