For the realization of the submarine detector NEMO it is necessary to design an acquisition system which is able to capture the signals coming from photo-multipliers (PMs) of the optical modules (OMs) and to satisfy several specifications: low power consumption; few submarine interconnections for reliability and simplicity of the deployment; flexibility of the system; minimum dead time; high dynamic range; accuracy in order to have good resolution. Here we present a Very Large Scale Integration full-custom solution for the OMs according to the requirements. It foresees to use a switched capacitor analog memory, a trigger and single photon classification system, a PLL and a control unit able to manage the different operation states of the whole system. For such a system we foresee a power dissipation not higher than 200–300 mV in each OM, 20 bit dynamic range and a dead time of about 0.1%.