The RD53 front-end chip's monitoring system is built around a 12-bit ADC connected to a multi-channel multiplexer. It makes it possible to digitize a variety of sensitive chip voltages, most notably the voltages generated by the on-chip temperature sensors, which are essential for offline temperature calculations.

Because the ADC reference voltage value increases under the effects of the total ionizing dose, there is a significant error when converting ADC output codes to voltages, making the direct temperature measurement unacceptable.

We present and explain a new approach for measuring temperature that won't rely on the shift in the ADC reference voltage. It offers more accurate temperature measurements even in situations with extreme radiation levels.

Based on this, a technique for correcting the ADC reference voltage value is proposed, and foreseen to be applied regularly during the operation of the pixel detector to increase the accuracy for the digitization of voltages or currents in the RD53 chip.