New High-Rate Timestamp Management with Real-Time Configurable Virtual Delay and Dead Time for FPGA-Based Time-to-Digital Converters

Modern applications require the ability to measure time events with high resolution, a full-scale range, and multiple input channels. Time-to-Digital Converters (TDCs) are a popular option to convert time intervals into timestamps. To reduce the time-to-market and Non-Recurring Engineering (NRE) costs, a Field-Programmable Gate Array (FPGA) implementation has been chosen. The high number of requested bits and channels, however, gives rise to routing congestion issues when routed in a parallel manner. In this paper, we will propose and analyze a novel solution, the Belt-Bus (BB), which involves a parallel-to-serial conversion of the timestamp stream coming from the TDC while maintaining chronological order and a sufficient high rate, and flagging the presence of timestamp overflow. Moreover, two new useful features are added. The first is a "Virtual Delay" to compensate for offsets due to cable length and FPGA routing path mismatch. The second is a "Virtual Dead-Time" to filter out unforeseen events. Finally, the BB was tested on a Xilinx 28 nm 7-Series Kintex-7 325T FPGA, achieving an overall data rate of 199.9 Msps with very limited resource usage (i.e., lower than a total of 4.5%), consuming only 480 mW in a 16-channel implementation.