Voltage-to-frequency converter with digital self-calibration using on-chip ring oscillator reference for radiation-tolerant sensor interfaces
Year: 2026
Type: article
Abstract: Radiation experts working on space-borne and high-energy physics sensor systems have long recognised that voltage-to-frequency converters (VFCs) offer a natural radiation tolerance that successive-approximation and delta-sigma ADCs lack, because the VFC’s core is a simple relaxation oscillator with no sensitive charge-storage nodes, yet the linearity of a conventional VFC degrades over time as total ionising dose shifts the threshold of the comparator and the charging current source. This research presents a self-calibrating VFC that uses an on-chip ring oscillator as a frequency reference and a lightweight digital engine to correct the conversion gain and offset in real time, restoring the linearity error to below 0.09% of full scale after calibration even when the uncalibrated error has drifted to 1.83%. The circuit was designed in a 180 nm bulk CMOS process and simulated across five process corners and a 200-run Monte Carlo campaign, with the radiation-induced parameter shifts modelled as systematic offsets to the comparator threshold and current-source Vt following the methodology of Faccio and Cervelli. The self-calibration cycle completes in 12 µs and repeats every 10 ms, consuming 0.7 mW from a 1.8 V supply including the ring oscillator and digital logic. The input range is 0.1–1.8 V, the output frequency spans 95–950 kHz, and the conversion resolution is 10 bits. Post-layout simulation confirmed that the calibration reduces the maximum linearity error from 1.83% to 0.09% of full scale across the full input range and across all five process corners, positioning the design as a drop-in radiation-tolerant sensor interface for satellite instrumentation and particle-detector readout systems.
Institution: University of Évora
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W7213321169