US 5,961,577 A · Random binary number generator

Abstract

A random number generator includes a plurality of fully differential amplifiers (30) configured as a ring oscillator (22). The output of the ring oscillator (22) is input to a comparator/latch circuit (32) for determining the zero crossing for the ring oscillator. The ring oscillator is a self-oscillating structure that has an oscillation frequency with jitter superimposed thereon. This jitter is a result of the internal thermal noise associated with the integrated circuits that are utilized to realize the amplifiers (30). Each of the amplifiers (30) that make up the ring oscillator operate on a substantially constant current and are subsequently isolated from changes in the power supply. As such, the variations in the frequency thereof are caused solely by thermal noise. The comparator/latch circuit (32) is operable to compare the difference on the output of the last stage of the ring oscillator (22) and the output of the comparator/latch (32) is then sampled by a CPU (12) that is operated on a separate master clock (18). This allows the master clock (18), upon which the sample operation is based, to be completely separate from the ring oscillator (22).

Claims8

Dependent claims

A random noise generator, comprising:

a plurality of differential inverting amplifiers of an odd number from "1" to "M" each with differential inputs and outputs and configured as a ring oscillator, with the output of each of said differential inverting amplifiers input to the input of only one of another of said differential inverting amplifiers, the output of said Mth differential inverting amplifier connected to the input of the first of said differential inverting amplifiers;
each of said differential inverting amplifiers operating with a substantially constant current and having thermal noise jitter associated therewith;
a comparator for comparing the positive and negative differential outputs of one of said differential inverting amplifiers and, when said difference is greater than a predetermined threshold, outputting a true logic signal, and when said difference is less than said predetermined threshold, outputting a false logic signal;
and
sampling circuitry for generating a sampling signal for sampling said comparator output N times to provide an N-bit random binary word.

2 more elements

Dependencies are inferred from the claim text.

Random binary number generator

Life of this patent

Random binary number generator

Life of this patent

Abstract

Claims8