A 33.6 ps LSB Time-to-Digital converter was designed in 130 nm BiCMOS technology. The core of the converter is a differential
9-stage ring oscillator, based on a multi-path architecture. A novel
version of this design is proposed, along with an analytical model
of linearity. The model allowed us to understand the source of the
performance superiority (in terms of linearity) of our design and to
predict further improvements. The oscillator is integrated in a
event-by-event self-calibration system that allows avoiding any
PLL-based synchronization. For this reason and for the compactness
and simplicity of the architecture, the proposed TDC is suitable for
applications in which a large number of converters and a massive
parallelization are required such as High-Energy Physics and medical
imaging detector systems. A test chip for the TDC has been
fabricated and tested. The TDC shows a DNL≤1.3 LSB, an
INL≤2 LSB and a single-shot precision of 19.5 ps (0.58
LSB). The chip dissipates a power of 5.4 mW overall.