Delay circuit having one of a plurality of delay lines which may be selected to provide an operation of a ring oscillator

摘要

The delay period of a delay circuit is maintained, over time, near to a desired delay, by generating information representative of the present delay period of the delay circuit, and altering the delay period, from time to time during operation, based on the present delay information and the desired delay. The present delay is measured by a reference circuit having a delay characteristic corresponding to the delay characteristic of the delay circuit. Both the reference and multiple delay circuits are formed with the same configuration on a single integrated circuit.