A neural processing unit may comprise a first circuit configured to perform operations for an artificial neural network (ANN) model, and arranged for a plurality of groups of processing elements (PEs) including a plurality of PEs; a second circuit arranged to output a plurality of clock signals to the first circuit; a third circuit configured to measure a ratio of peak power and average power of at least the first circuit; and a fourth circuit, arranged to dynamically calibrate a phase of at least one of the plurality of clock signals of the second circuit based on the ratio of peak power and average power measured in the third circuit.