An interpolating time-to-digital converter on an FPGA

A simple and sufficiently precise unit converting single time intervals to digital codes on an EP2C20F484C7N Altera field programmable gate array is proposed. The resolution of the converter, the principle of operation of which is based on interpolating the reference period by a great number of outputs of a ring pulse oscillator, is determined by the delay time of the oscillator stage and is 315 ps. The converted interval range is 2.58 μs, and the “dead” zone between adjacent conversions does not exceed 5 ns. The circuit does not need any adjustments and is insensitive to supply voltage and environment temperature deviations.