Patent ID: 7816890

Claim:
A semiconductor unit for protecting a secondary battery by detecting overcharge, overdischarge, charging overcurrent, discharging overcurrent or short circuit current, comprising: a current detecting terminal converting a charging current into a negative voltage with respect to a negative electrode potential (ground potential) of the secondary battery when the secondary battery is charged, converting a discharging current into a positive voltage with respect to the negative electrode potential of the secondary battery when the secondary battery is discharged and detecting the charging/discharging current; and a test signal generating circuit generating a first test signal when a voltage of the current detecting terminal is reduced to a first negative voltage which does not occur in a normal operation state of the semiconductor unit, and generating a second test signal when the voltage of the current detecting terminal is reduced to a second negative voltage which is lower than the first negative voltage, wherein the test signal generating circuit at least comprises: a first inverter circuit of a CMOS configuration in which, for the purpose of generating the first test signal, a negative power supply terminal thereof is connected to the current detecting terminal, and an input terminal thereof is connected to a ground potential or a predetermined potential, and a second inverter circuit of a CMOS configuration in which, for the purpose of generating the second test signal, a negative power supply terminal thereof is connected to the current detecting terminal, and an input terminal thereof is connected to the ground potential or the predetermined potential.