Patent ID: 8786289

Claim:
A semiconductor device for monitoring a plurality of unit batteries having respective positive and negative terminals, the unit batteries being connected in series, the semiconductor device comprising: a selector switch including a plurality of switching elements for selecting one of the unit batteries and outputting a first voltage obtained from the positive terminal of the selected unit battery and a second voltage obtained from the negative terminal of the selected unit battery; a first buffer amplifier having a first high-impedance input terminal for receiving the first voltage from the selector switch and blocking flow of current from the selector switch, and a first output terminal for output of a voltage corresponding to the first voltage; a second buffer amplifier having a second high-impedance input terminal for receiving the second voltage from the selector switch and blocking flow of current from the selector switch, and a second output terminal for output of a voltage corresponding to the second voltage; and a level shifter connected to the first output terminal of the first buffer amplifier and the second output terminal of the second buffer amplifier, for outputting a shifted voltage corresponding to a difference between the first voltage and the second voltage.