TIME-TO-DIGITAL CONVERTERS BASED ON RSPQ DIGITAL COUNTERS

We have designed, fabricated, and successfully tested a Time-to-Digita l converter (TDC). The TDC circuit consists of superconductive counter s based on toggle flip-pops with destructive readout, shift registers, parallel-to-serial converters, and pulse detectors. The value of the counter is latched while the counter is operating at full speed. The T DC resolution is directly determined by the maximum counter speed, or 50ps for an available 20GHz clock rate. The circuits are implemented i n HYPRES' standard Nb process with a critical current density of 1.0 k A/cm(2) using HYPRES' Library of standard RSFQ cells.