Rohm Co., Ltd.

Yutaka Shibata

Koichi Miyanaga

Ichiro Yokomizo

Akihito Ito

A voltage comparison circuit makes a comparison between a first voltage and a second voltage. A resistor and a constant current source are provided in series between the first voltage and the ground voltage. A comparator receives the second voltage via one input terminal (non-inverting input terminal), and the voltage at a connection node between the aforementioned resistor and the constant current source via the other input terminal (inverting terminal). The first voltage is preferably used as the power supply voltage for the comparator.

Voltage comparison circuit

An external power source is connected to an adapter input terminal (first terminal). A battery is connected to a path input terminal (second terminal). A selection circuit (a first switch, a second switch, logic circuit compares the input voltage input from the external power supply with the battery voltage, and selects one of the two. The voltage thus selected by the selection circuit is output to an external load circuit via a system power supply terminal. A charging circuit charges the battery using the input voltage supplied from the external power supply.

Power management circuit

A current-voltage conversion circuit which converts a current to be detected into a voltage, includes a detection resistor, amplifier circuit having a first operational amplifier, and an offset adjusting current source having a third resistor and a fourth resistor which are capable of trimming. The offset adjusting current source causes an offset adjustment current to flow in the offset resistor. The current value of the offset adjustment current is controlled by adjusting the resistance of the third resistor and the fourth resistor. A voltage at a node between the first transistor and the second resistor is output.

Growing community of inventors

Kyoto, Japan

Yutaka Shibata