Zero crossing-current ring oscillator for substrate charge pump

Abstract

A ring oscillator for use with a charge pump includes an odd number of inverter stages each having a primary input, a secondary input, and an output. Both inputs are switched to the same logic state to invert the logic signal at the output of the inverter stage. No crossing-current flows within the inverter stage if the inputs have different logic states. The output of each inverter stage is coupled to the primary input of a following inverter stage in a serially-connected ring fashion. The output of a last inverter stage is coupled to the primary input of a first inverter stage and forms an oscillating signal output, which is coupled to the charge pump. The secondary input of each stage is coupled to the output of a preceding inverter stage. The preceding inverter precedes the current inverter by an odd integer greater or equal to three. The ring oscillator includes a transistor coupled to the output of each inverter stage for impressing a initial pattern of alternating logic levels to begin the oscillation.

Dependencies are inferred from the claim text.