Timing measurement BOST with multi-bit delta-sigma TDC

This paper describes design and implementation of a multi-bit delta-sigma (ΔΣ) Time-to-Digital Converter (TDC) with Data-Weighted-Averaging (DWA) algorithm on analog FPGA. I/O interfacing circuits such as double-data-rate (DDR) memory interfaces are very important, and their low-cost, high-quality test is challenging. We propose here simple test circuitry for measuring digital signal timing of I/O interfacing circuits with high resolution and good accuracy. We focus on TDC applications of ΔΣmodulators (for fine-timing-resolution, digital output, and simple circuitry) and with multi-bit architecture (for short testing time). However, the multi-bit ΔΣ TDC suffers from delay mismatches among delay cells. Then we propose to apply the DWA algorithm for the delay cells in order to solve this problem. Our experimental results showed that the DWA algorithm improved the overall multi-bitΔΣ TDC linearity.