An energy-harvesting device comprising: a power management module ; and detector circuitry for controlling the operation of the power management module , the detector circuitry comprising: an input for receiving an electrical input representative of a level of harvestable power; and a trigger coupled to the input and operable to generate an activation signal for switching on the power management module ; wherein the trigger is configured to generate the activation signal upon detecting at least a threshold level of harvestable power, and thereby switch on the power management module ; and wherein the trigger is configured not to generate the activation signal upon detecting less than the threshold level of harvestable power, and thereby switch off the power management module ; wherein the trigger comprises a non-inverting Schmitt trigger; characterised in that the power management module is configured to perform maximum power point tracking in a sampling time-window that is immediately at the start-up of the power management module by the trigger, synchronized with the presence of input harvestable power; and wherein the input of the detector circuitry is configured to receive an electrical input from a radio frequency, RF, antenna, representative of a level of harvestable power from an RF source. a power management module ; and detector circuitry for controlling the operation of the power management module , the detector circuitry comprising: an input for receiving an electrical input representative of a level of harvestable power; and a trigger coupled to the input and operable to generate an activation signal for switching on the power management module ; wherein the trigger is configured to generate the activation signal upon detecting at least a threshold level of harvestable power, and thereby switch on the power management module ; and wherein the trigger is configured not to generate the activation signal upon detecting less than the threshold level of harvestable power, and thereby switch off the power management module ; wherein the trigger comprises a non-inverting Schmitt trigger; characterised in that the power management module is configured to perform maximum power point tracking in a sampling time-window that is immediately at the start-up of the power management module by the trigger, synchronized with the presence of input harvestable power; and wherein the input of the detector circuitry is configured to receive an electrical input from a radio frequency, RF, antenna, representative of a level of harvestable power from an RF source. an input for receiving an electrical input representative of a level of harvestable power; and a trigger coupled to the input and operable to generate an activation signal for switching on the power management module ; wherein the trigger is configured to generate the activation signal upon detecting at least a threshold level of harvestable power, and thereby switch on the power management module ; and wherein the trigger is configured not to generate the activation signal upon detecting less than the threshold level of harvestable power, and thereby switch off the power management module ; wherein the trigger comprises a non-inverting Schmitt trigger; characterised in that the power management module is configured to perform maximum power point tracking in a sampling time-window that is immediately at the start-up of the power management module by the trigger, synchronized with the presence of input harvestable power; and wherein the input of the detector circuitry is configured to receive an electrical input from a radio frequency, RF, antenna, representative of a level of harvestable power from an RF source. <EOS>