Time-to-digital converter

Time-to-Digital Converters (TDC) are electronic assemblies that measure short time intervals and convert them into digital output. Strictly speaking, this also includes simple frequency counters . However, it is customary to speak of a TDC only if the time resolution is better than can be achieved directly with counters. This is currently the case from a resolution of around 1 ns.

Single hit TDCs

A single-hit TDC is not immediately ready for use again after a measurement, but has a dead time that is relatively high compared to the measured interval. If this restriction is acceptable, e.g. B. 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 makes use of gate delay times in frequency- stabilized ring oscillators , with a phase-locked loop with a quartz reference regulating the operating voltage of the ring oscillator.

Multi-hit TDCs

If several events have to be measured very close to one another, techniques are usually used that interpolate a clock cycle directly, often using self-calibrating gate delay chains. Such TDCs achieve resolutions down to about 10 picoseconds .

Such a TDC does not output the size of an individual time interval, but a list of pulse arrival times.

Areas of application for multi-hit TDCs are e.g. B .:

mass spectrometry
LIDAR
experimental basic research, especially atomic physics .
Time correlated single photon counting

Designs

Time-to-digital converters are both integrated circuits, discrete circuit parts, system components (e.g. PC plug-in cards) and stand-alone measuring devices. The latter are usually referred to as time interval counters.

Integrated TDC circuits are manufactured by ACAM in Stutensee / Karlsruhe in Germany and by Texas Instruments in the USA .

Web links

German manufacturer of TDC plug-in cards for PCs

Individual evidence

↑ TDCs - Time-to-Digital Converters. ACAM, 2014, accessed December 3, 2015 .
↑ TDC7200 Time-to-Digital Converter for Time-of-Flight Applications in LIDAR, Magnetostrictive and Flow Meters. (PDF; 1.5 MB) Texas Instruments , August 2015, accessed on December 3, 2015 .

[ACAM_1-1] TDCs - Time-to-Digital Converters. ACAM, 2014, accessed December 3, 2015 .

[TI_1-2] TDC7200 Time-to-Digital Converter for Time-of-Flight Applications in LIDAR, Magnetostrictive and Flow Meters. (PDF; 1.5 MB) Texas Instruments , August 2015, accessed on December 3, 2015 .