PURPOSE: To detect trouble such as disconnection or earthing without delay.
CONSTITUTION: The first resistor R11 connected to a transistor T-1 in parallel, the second resistors R22, R23 connected across an input terminal IN and earth, a first comparator CMP1 inputting the input potential Vin proportional to the potential of the input temtinal IN and first reference potential Vref1, a second comparator CMP2 inputting the input potential Vin and third reference potential Vref2 and a third comparator CMP3 inputting the input potential Vin and third reference potential Vref3 are provided. By setting the first, second and third reference potentials Vref1, Vref2, Vref3 to predetermined relation, the output level of the first comparator is changed corresponding to ON/OFF of the transistor and, in the case of earthing trouble and disconnection trouble, the outputs of the second and third comparators can be reversed and abnormality can be detected on the basis of this reversal without delay.
HASEDA TETSUSHI
TSUZUKI YOSHIHIKO
NAKAMURA MITSUO
INABA TAKASHI
