Latha P, Sivakumar R, and Ramana Rao Y.V. Multichannel Ring Oscillator Based Time Interval Measurement with Binwidth Calibration. Dynamic Systems and Applications 30 (2021) No.6, 1003-1014

https://doi.org/10.46719/dsa20213067

ABSTRACT.  
Time to digital converters (TDC) is used to calculate a time interval between two occurrences in digital domain. They are used in the field of communication for laser range finding, Nuclear reactor and calibration tools in measuring techniques. Most industrial applications use Application Specific Integrated Circuits (ASICs) for time interval measurement. But, with the increasing technological trends, there arises a need for high performance, low nonlinearity measurement devices with better flexibility and resolution. The proposed work is implementation of Multichannel Time interval measurement using the ring oscillator approach along with bin-width calibration using Xilinx 14.1 ISE and Spartan-6 Field Programmable Gate Array (FPGA). In Multichannel architecture the channels influence each other during the operation and minimizes the linearity error. In order to compensate for process, voltage and temperature fluctuations and changes resulting from the ionizers, the ring oscillator is positioned within Phase Locked Loop (PLL). It also decreases the complexity of the circuit by minimizing the number of delay elements. Bin by bin calibration is used to reduce the bin widths Variations. A very large number of events need to be obtained to maximize the calibration time if high-precision calibration is needed in order to minimize statistical fluctuation. Calibration monitors and controls errors or uncertainties to an appropriate level for the calculation procedure. As a consequence, the relative phases of two input clock signals are highly precise. Therefore, precision time measurements with low cost and good efficiency are carried out in our implementation.

Index Terms—Delay Locked Loop (DLL), Digital Phase Locked Loop (DPLL), Universal Asynchronous Receiver Transmitter (UART), bin-width, Ring Oscillator (RO), Time to Digital Converter (TDC)