The term time-to-digital converter is used when talking about time interval measurements in the range of 1 nanosecond down to the picosecond range. The first TDC's have deen developed for scientific and research purposes. They have been realized as a combination of time-to-analog (TAC) and analog-to-digital (ADC) converter. A sophisticated design of the TAC together with limitations to update rate or multihit capability make these solutions inattractive for industrial applications.

Integrated digital TDC's

Thanks to modern CMOS technology it is possible to integrate fully digital time-to-digital converters into a single chip. The high precision - down to 14 ps - in combination with the large dynamic range (up to 30 Bit), the high stability over temperature and supply voltage and the possibilty of a low cost production thanks to the CMOS technology make them to the first choice for industrial applications.