US Patent 9454212 Wakeup detector

Systems and methods related to wakeup circuits for electronic devices are disclosed. More particularly, an electronic device includes a component operable in at least a lower power state and a higher power state and a wakeup circuit configured to signal the component to transition from the lower power state to the higher power state upon declaration of a wakeup event. The wakeup circuit is configured to process a received input signal to synchronize with a clock; generate an activity signal that includes an activity pulse for each time the processed input signal changes state in different cycles of the clock; open a qualification window upon detection of a first activity pulse in the activity signal; and in the event more than a threshold number of activity pulses in the activity signal are detected prior to closing the qualification window, declare a wakeup event.