Precise delay generation using coupled oscillators

Abstract

An array oscillator, a series of coupled ring oscillators that achieves a delay resolution equal to a buffer delay divided by the number of rings, is described. Using a 2-mu m n-well CMOS technology, delays as small as 30 ps are achieved at frequencies up to 200 MHz. An array oscillator structured as a two-dimensional array of buffers is shown. The integral linearity and differential nonlinearity versus position in the-22 mode measured from the output ports are shown. The frequency sensitivity to static supply voltage in the-12 mode is investigated. The measured static frequency rejection is less than 0.25% over most of the operating range for each mode. The characteristics and performance of the array oscillator as a voltage-controlled oscillator for each mode are summarized.