Random number generator with ring oscillation circuit

摘要

A random number generator includes a ring oscillator having an EX-OR gate and four inverters together forming a loop. This loop enters stable state for a start signal having the low level and oscillates for the start signal having the high level. When the start signal has a pulse of a width shorter than the loop's delay time, output nodes responsively, sequentially enter metastable state hovering between the high and low levels. The metastable waveform becomes smaller with time and finally disappears. As metastable state cannot be controlled in longevity, it disappears at any random number node. A counter thus outputs a signal serving as true random number data depending on the longevity of the metastable state. A random number generator miniaturized and having reduced power consumption, and of high performance can thus be implemented.

主权项

1. A semiconductor apparatus comprising:
a central processing unit which provides a request signal; a random number storing circuit; and a random number generating circuit, which comprises a ring oscillator including a plurality of gate circuits, a signal generator receiving the request signal and providing a start pulse whose width is shorter than a total delay time of the plurality of gate circuits and a counter counting a number of output signals from the plurality of gate circuits, wherein the random number generating circuit generates a first random number by counting with the counter the number of output signals from the plurality of gate circuits during a predetermined period, which is determined by a time of a metastable being disappeared in the ring oscillator, after the ring oscillator receiving the start pulse, and the random number storing circuit stores the first random number generated by the counter in the random number generating circuit as a random number, and outputs the random number to the central processing unit in accordance with a read request from the central processing unit.