and operation voltage v cc equivalently corresponds to the variation slope of operation voltage v cc for example the quicker operation voltage v cc drops the more filtered voltage v cc lpf exceeds operation voltage v cc when inverted ovp signal s ovp b outputted by comparator 64 is u201c 1 u201d in logic multiplexer 66 couples over voltage reference v ref ovp to the non inverted input of comparator 64 in the opposite when inverted ovp signal s ovp b is u201c 0 u201d in logic multiplexer 66 couples filtered voltage v cc lpf to the non inverted input of comparator 64 accordingly if inverted ovp signal s ovp b is u201c 1 u201d it implies that operation voltage v cc might not have been too high and comparator 64 compares operation voltage v cc with over voltage reference v ref ovp to check whether operation voltage v cc is too high at this moment if inverted ovp signal s ovp b is u201c 0 u201d it implies that operation voltage v cc has been too high and comparator 64 compares operation voltage v cc with filtered voltage v cc lpf equivalently detecting the variation slope of operation voltage v.