A plurality of digital circuits are manufactured from an identical circuit design. A power controller is operatively connected to the digital circuits, and a non-transitory storage medium is operatively connected to the power controller. The digital circuits are classified into different voltage bins, and each of the voltage bins has a current leakage limit. Each of the digital circuits has been previously tested to operate within a corresponding current leakage limit of a corresponding voltage bin into which each of the digital circuits has been classified. The non-transitory storage medium stores boundaries of the voltage bins as speed-binning test data. The power controller controls power-supply signals applied differently for each of the digital circuits based on which bin each of the digital circuit has been classified and the speed-binning test data.