A 16-channel, multi-level Time-to-Digital Converter for high precision ToF measurement

A 16-channel Time-to-Digital Converter (TDC) with high precision and high linearity for time of flight (ToF) measurement is presented. The 3-level Nutt-based structure is employed in the proposed TDC to achieve high resolution and wide dynamic range simultaneously. A novel vernier measurement structure based on two Delay Locked Loops (DLLs) with different frequencies is proposed in this work, with which 10-ps resolution can be achieved with less jitter accumulation and moderate frequency. The proposed 16-channel TDC is implemented using 180-nm standard CMOS process with 1.8-V power supply. Under the operating clock frequencies of 240-MHz and 280-MHz, the TDC is realized with a resolution of 10.6-ps and a dynamic range of 1066-ns. According to testing results, the best single-shoot precision of 13.7-ps and good consistency among all channels can be observed. In asynchronous measurements, the maximum differential nonlinearity (DNL) and the integral nonlinearity (INL) are less than 0.5-LSB and 1-LSB respectively.