We present a radiation-tolerant 120 dB dynamic-range interface circuit for ionization chambers and diamond detectors. The device consists of a multi-scale continuous-time incremental charge-to-digital converter paired with a temperature-compensated current reference. The circuit selects the sensitivity according to the input signal level and provides a 20-bit plus sign output code every 40 mu s. The proposed interface circuit achieves a measurement linearity error better than +/- 5% in the 40 fC-42 nC range. The ASIC has been designed for radiation-tolerance in a 0.25 mu m 3M1P CMOS technology and tested for TID up to 100 kGy(Si), showing uninterrupted functionality. The conversion reference drifts of 3% at 100 kGy(Si) and its temperature coefficient is less than 600 ppm/degrees C. (C) 2013 Elsevier Ltd. All rights reserved.