A 71PS-RESOLUTION MULTI-CHANNEL CMOS TIME-TO-DIGITAL CONVERTER FOR POSITRON EMISSION TOMOGRAPHY IMAGING APPLICATIONS

This paper presents a high-resolution multi-channel Time-to-Digital Converter (TDC) for Positron Emission Tomography (PET) imaging system. The TDC using a two-level conversion scheme is proposed for obtaining high timing resolution. Double 10-bit gray counters are designed for coarse conversion while a multiphase sampling technology is presented for fine conversion. In order to achieve better timing resolution with either a faster technology, an array of Delay-locked loops is chosen as a timing generator. A prototype chip of 3-channel TDC is designed and fabricated in AMS 0.35 mu m CMOS technology. The area of the chip is 8.4 mm(2) in size. The measured range of the TDC is 10 mu s. The time tap is reduced to 71 ps with a reference clock of 100MHz. The differential nonlinearity is +/-0.1LSB. The circuits will be extended to 64 channels for small animal PET imaging systems.