Patent ID: 7477244

Claim:
In a display controller having an on-board power supply and a reference clock signal generator circuit arranged to generate a reference clock signal (T CLK ), an auto activity detection circuit, comprising: an input node coupled to the reference clock signal generator circuit; a first resistor is connected to an input node and a capacitor; a capacitor connected to the first resistor at a node N 1 and a second resitor; a second resistor having a second resistor first terminal connected to the capacitor second terminal and a second resistor second terminal connected to the node N 1 ; an output node coupled to the node N 1 , wherein when the reference clock signal generator circuit is generating the reference clock signal (T CLK ), the capacitor charges the node N 1 to a high voltage that, in turn, drives the output node to HIGH indicating that the reference clock generator circuit is in fact generating the reference clock signal (T CLK ); a first inverter having an input coupled to the node N 1 and a first inverter output; and a second inverter having a second inverter input coupled in series with the first inverter output and a second inverter output coupled to a node N 2 .