Standard cell ring oscillator of a non-deterministic randomizer circuit

Abstract

A digital standard cell implemented ring oscillator circuit for placement within an integrated circuit device. In one embodiment, the digital standard cell ring oscillator circuit is used in conjunction with a system for generating non-deterministic (e.g., random) output signals which can be used for data encryption. A random number generator circuit is used within the above system and the standard cell ring oscillator of the present invention is used to provide oscillator signals to different frequency legs of the random number generator circuit and can also be used to supply a jitter clock. The timing characteristics (e.g., frequency) of the standard cell ring oscillator vary with its fabrication process, its fabrication environment, and the temperature when used; timing characteristics are therefore unpredictable from 'chip' to 'chip' and from one point in time to another with respect to the same 'chip.' This increases the non-deterministic properties of the random number generator. By using a standard cell ring oscillator in lieu of a custom analog oscillator, the present invention oscillator is readily portable from one design environment to another, is readily modifiable to realize different frequencies, and provides a more dense integrated circuit layout because the oscillator of the present invention can be integrated within other standard cell layout areas of the integrated circuit and also eliminates block to block routing resources. This latter characteristic makes the oscillator difficult to locate within the integrated circuit layout, increasing the difficulty of externally compromising the random number generation.