A calibration technique for a high-resolution flash time-to-digital converter

Traditional flash time-to-digital converters (TDCs) make use of buffers delays and flip-flops or arbiters to quantize a time interval. To achieve high resolution without delay buffers however, offsets caused by mismatches in arbiter layout can be used for time quantization. Such a flash converter requires a calibration technique to determine these offsets. This paper describes a direct calibration method based on the addition of a temporal noise to the arbiter input. Such a technique eliminates the need for very small input times as in a traditional direct calibration. Simulation results reveal that the proposed calibration technique, followed by a curve-fitting procedure, can be used to accurately determine arbiter offset down to picoseconds.