An integrated circuit comprises a plurality of sensing circuits (12), each for detecting whether a respective physical operating parameter is above or below a respective reference value. The integrated circuit contains a serial shift register (11) for shifting digital data signals that represent the respective reference values from a successive approximation update circuit (14) to the sensing circuits (12) and back to the successive approximation update circuit (14). Detection results of the sensing circuits (12) are shifted to the successive approximation update circuit (14) with the digital data signals. The successive approximation update circuit (14) is used to form the digital data so that the reference values form successive approximations of the physical operating parameter values during an analog to digital conversion process. In this way the successive approximation update circuit (14) is shared by a plurality of sensing circuits (12).