A Review of New Time-to-Digital Conversion Techniques

Time-to-Digital Converters (TDCs) are vital components in time and distance measurement and frequency locking applications. There are many architectures for implementing TDCs, from simple counter TDCs to hybrid multi-level TDCs which use many techniques in tandem. This paper completes the review literature of TDCs by describing new architectures along with their benefits and trade-offs, as well as the terminology and performance metrics that must be considered when choosing a TDC. It describes their implementation from the gate level upwards and how it is affected by the fabric of the device (FPGA or ASIC) and suggests suitable use cases for the various techniques. Based on the results achieved in the current literature, we make recommendations on the appropriate architecture for a given task based on the number of channels and precision required, as well as the target fabric.