Patent ID: 7893656

Claim:
A semiconductor integrated circuit device comprising: a supporting substrate; a semiconductor layer disposed on the supporting substrate and electrically isolated from the supporting substrate; a plurality of input terminals connected to positive and negative terminals of a plurality of secondary cells, which are connected in series to construct an assembled battery; and a plurality of circuit elements formed to the semiconductor layer and electrically isolated from each other, wherein the plurality of circuit elements provide a plurality of monitor circuits, each monitor circuit being provided to a corresponding one of the plurality of secondary cells to monitor a cell voltage of the corresponding secondary cell, wherein each monitor circuit includes a cell voltage detection circuit, a reference voltage generation circuit, and a comparison circuit, wherein the cell voltage detection circuit divides a voltage between the input terminals connected to the positive and negative terminals of the corresponding secondary cell and detects the cell voltage based on the divided voltage, wherein the reference voltage generation circuit generates a reference voltage from the cell voltage, wherein the comparison circuit compares the divided voltage with the reference voltage and outputs a first monitor signal in accordance with a result of the comparison, and wherein the comparison circuit is powered by a voltage between the input terminals connected to a first one of the positive terminals of the plurality of secondary cells and a first one of the negative terminals of the plurality of secondary cells, a voltage of the first one of the positive terminals being equal to or greater than a voltage of the positive terminal of the corresponding secondary cell, a voltage of the first one of the negative terminals being equal to or less than a voltage of the negative terminal of the corresponding secondary cell, wherein the plurality of circuit elements further provide first, second, and third switch circuits, wherein the first switch circuit and the cell voltage detection circuit are connected in series between power supply lines of the monitor circuit, wherein the second switch circuit and the reference voltage generation circuit are connected in series between the power supply lines, wherein the third switch circuit and the comparison circuit are connected in series between the power supply lines, and wherein all the first, second, and the third switch circuits are turned on/off at a same timing in accordance with a common on/off signal.