Time-to-Digital-Converter

Time-to- Digital Converter (TDC ) are electronic devices that measure short time intervals and convert it into a digital output. Strictly speaking, this also includes simple frequency counter. It does, however, only to speak of a TDC when the time resolution is better than can be achieved directly with counters. Currently, this is from a resolution of about 1 ns the case.

Single -hit TDCs

A single -hit TDC is not ready for use immediately after a measurement, but has a dead time, which is relatively high compared to the measured interval. If this limitation is acceptable, for example, in the trigger logic of an oscilloscope, the time measurement can be done indirectly, and a higher resolution can be achieved. Currently down to about 100 femtoseconds. The TDC uses the use of gate delays in frequency-stabilized ring oscillators, with a phase-locked loop with quartz reference controls the operating voltage of the ring oscillator.

Multi-hit TDCs

If multiple events to be measured very close together, usually come techniques used, which interpolate one clock cycle directly. Often self-calibrating gate delay chains. Such TDCs achieve resolutions down to about 10 picoseconds.

Such TDC is not the size of a single time interval, but rather a list of pulse arrival times.

Applications for multi-hit TDCs are eg:

• Mass spectrometer
• LIDAR
• Experimental basic research, especially atomic physics.
• Time-correlated single photon counting

Designs

As time-to- digital converter is referred to both integrated circuits, discrete circuit components, system components (eg PC cards ) as well as stand-alone instruments. The latter are usually referred to as a Time Interval Counter.

Integrated circuits provide TDC in Germany manufactures the company ACAM and MSC in Stutensee / Karlsruhe.

German manufacturer of TDC plug-in for PCs are cronologic, FastComTec, PicoQuant and Becker Hickl.