A power management circuitry for a radar level gauge including a first voltage converter, having a low-voltage end for receiving a drive voltage from a power interface and a high-voltage end for supplying an intermediate voltage higher than the required operating voltage, a temporary energy store arranged to be charged by the intermediate voltage, a second voltage converter, having a high-voltage end for receiving an input voltage from the energy store, and a low-voltage end for providing the operating voltage lower than the input voltage.By storing energy at a higher voltage, a different type of energy store (e.g. low capacity capacitor) may be used. As a consequence, the cost and start-up time of the energy store is significantly reduced.