Monolithic Time-to-Amplitude converter for TCSPC applications with 45 ps time resolution

In recent years many applications exploiting the measurement technique of time-correlated single photon counting (TCSPC), that allows the analysis of extremely fast and weak light waveforms with a picoseconds resolution, have been developed in several fields such as medicine and chemistry. Moreover, the development of single photon avalanche diode arrays and of multianode PMT led to the realization of acquisition systems with several parallel channels to employ the TCSPC technique in even more applications. One of the most important sections of a TCSPC acquisition chain is the time measurement block, which must present high resolution and low differential nonlinearity, and in order to realize multidimensional systems, it has to be integrated to reduce both cost and area. In this paper we present a fully integrated Time-to-Amplitude converter (TAC), built in 0.35 μm Si-Ge technology, characterized by a very good time resolution (45 ps), low differential nonlinearity (better than 4% peak to peak and 0.2% rms), high counting rate (16 MHz), low and constant power dissipation (less than 50 mW), and low area occupation (1.38×1.28 mm²).