A high-resolution multi-channel time-to-digital converter (TDC) for high-energy physics and biomedical imaging applications

This paper presents the design of a wide-range multi-channel time-to-digital converter (TDC) for high-energy physics and biomedical imaging applications. The TDC architecture is based on coarse-fine two-level conversion scheme. Double 10-bit gray counters are designed for coarse conversion while a multiphase sampling technology based on array of delay-locked loops is proposed for fine conversion. The resolution range is achieved from 71 ps to 142 ps by use of a reference clock from 100 MHz to 50 MHz. The measured range of the TDC is 10 mus. A prototype chip of 3-channel TDC for PET imaging system is designed and fabricated in AMS 0.35 mum CMOS technology. The area of the chip is 8.4 mm² in size. The differential nonlinearity is plusmn0.1 LSB. The integral nonlinearity is plusmn0.1 LSB. The circuits will be extended to 64 channels for small animal PET imaging system.