Detecting when the on-board power supply is powered on or off by an auto activity detection circuit by determining if the reference clock signal (TCLK) is toggling and if the reference clock signal is toggling, then charging a capacitor to a high voltage in the auto activity detection circuit based on the toggling reference clock signal, and outputting an on-board power supply activity signal based upon the high voltage by the auto activity detection circuit indicative of whether or not the on-board power supply is active.