At least one embodiment provides a method for a nanopower boost regulator to startup from an ultra-low-voltage (such as 0.3V˜0.5V) for energy harvesting applications. The method does not necessarily require a special process or any external components such as mechanical switches. The startup circuit can include an asynchronous boost circuit to charge up an output with stacked power NMOS transistors, a ring oscillator, and/or a charge pump, along with accompanying circuitry.