A High-resolution Time-to-digital Converter with a Time-stretching Technique in a General-purpose Microcontroller

Abstract

Time-to-digital converters (TDCs) are electronic devices used in systems that require precise measurement of time intervals. These devices transform temporal information into digital form. Traditionally, the resolution of TDCs built on general-purpose microcontrollers (MCUs) has been limited by the reference clock frequency, which typically does not exceed 80 MHz. Recent advances in quasi-digital techniques offer practical solutions to overcome this limitation, primarily through time-stretching and analog interpolation. This article presents a new high-resolution TDC architecture that incorporates a time-stretching technique within a 16-bit MCU and two analog interpolators, implemented via direct-interface circuits. A time interval resolution of 4 ns was achieved over a range of 10 μs to 16 ms using a 4 MHz reference clock. This performance is comparable to that of a 240 MHz digital counter, representing a sixty-fold improvement in effective clock resolution. The proposed architecture is well-suited for portable, low-power applications that do not compromise measurement accuracy.