US Patent 7671643 Power-on-reset circuit having zero static power consumption

A power-on-reset (POR) circuit having a zero or substantially zero current state while the supply voltage is in a predetermined, valid range is disclosed. The POR circuit includes a state machine, an oscillator, and output circuitry that are electrically coupled to one another and to a supply voltage. Output from the output circuitry is also provided to the integrated circuit to which the POR circuit is coupled. The state machine includes a plurality of sequential circuits such as latches, flip-flops, and the like that are electrically coupled in a cascade, to provide a ripple counter. The output circuitry is structured and arranged to reset or initialize all of the logic elements on the chip by generating a POR output logic HI (1) signal by Boolean operation of the logic circuitry signal of the state machine for all Boolean states except one. The oscillator is disabled when the POR output logic signal is LO (0), which causes the POR circuit to enter a zero or substantially zero current state.