Time-to-digital converter resolves 10 psec for accurate laser ranging

January 25, 2017 // By Graham Prophet
From ams (Premstaetten, Austria) the TDC-GPX2 measures time intervals at a resolution of up to 10 psec for ultra-accurate time-of-flight measurements in laser ranging and medical scanning applications, claiming the best-available combination of speed, precision and power.

This IC is an update of ams’ time-to-digital converter (TDC) offering improved speed and precision together with low power consumption. The TDC-GPX2 also features standard low-voltage differential signalling (LVDS) and serial peripheral (SPI) interfaces, and a smaller 9 x 9 mm QFN64 package.


TDCs from ams, which can measure short time intervals with great precision, are used in light detection and ranging (LIDAR) and laser-ranging devices, in positron emission tomography (PET) medical scanners, and in automated test equipment (ATE). The introduction of the TDC-GPX2 means that these applications gain increased resolution up to 10 psec and a sampling rate of up to 70 Msamples/sec.


The TDC-GPX2 is an integrated four-channel converter IC offering single-measurement resolution of up to 20 psec rms per channel in normal mode. Operating in dual-channel high-resolution mode, it can achieve a maximum resolution of 10 psec rms with 5 nsec pulse-to-pulse spacing.

The performance of the TDC-GPX2 has been achieved without sacrificing power efficiency: it uses between 60 mW and 450 mW in normal operation, and draws 60 µA in stand-by mode.

ams adds that the TDC-GPX2 is easy to implement in end-product designs, providing standard interfaces and requiring few external components. The chip also includes a driver for a quartz reference clock, which can be used for automatic calibration alternatively to the reference input. There is an evaluation kit, the GPX2-EVA-KIT, which includes a programmer and GUI software for PCs, enabling users to configure and connect their Start and Stop signals and begin taking sample time measurements.


ams; http://ams.com/Time-to-Digital-Converters/TDC-GPX2