NOVELTY - The circuit has a power source voltage output circuit supplying power source voltage (VCC2) to a communication circuit and outputting the power source voltage externally. A VCC1 terminal is directly connected to a power source line (13) for supplying reference voltage (VCC1) to another communication circuit. A VCC2 terminal is connected to a measurement semiconductor circuit (20-1) at a higher level for supplying power source voltage of the measurement semiconductor circuit to the latter communication circuit, as another power source voltage.    USE - Semiconductor circuit for use in a system for monitoring and controlling voltage of battery cells of a high output battery i.e. lithium-ion battery, for driving a motor of a hybrid vehicle and an electric vehicle.    ADVANTAGE - The circuit allows a reference voltage terminal to be directly connected to a power source line, so that sudden voltage change is generated without cutting noise and potential difference between the voltages becomes constant regardless of the voltage change, thus avoiding change of the communication signal input into an input/output circuit and avoiding logic inversion, and hence preventing false operation. The reference voltage terminal is directly connected to the power source line such that the reference voltage is supplied to an integrated circuit from the reference voltage terminal, so that reference voltage changes according to the change in battery voltage due to load current and the power source voltages are supplied to the integrated circuit from the measurement semiconductor circuit at the higher stage through the power source voltage terminal changes, thus allowing the potential difference between the voltages to be constant, avoiding the communication signal to be affected and preventing the false operation, and hence performing the signal communication regardless of the battery voltage change in an proper manner.    DESCRIPTION OF DRAWING(S) - The drawing shows a circuit block diagram of a battery monitoring system.    Reference voltage (VCC1)    Power source voltage (VCC2)    Semiconductor device (10)    Control semiconductor circuit (12)    Power source line (13)    Batteries (14)    Battery cell groups (15-1, 15-2)    Measurement semiconductor circuits (20-1, 20-2)    Logic circuits (24-1, 24-2)