Patent ID: 8214659
Filing Date: 2012-07-03
Classification: H03K

Abstract:
1. A communication device, comprising: a bus, including a signal line supplied with a pull-up voltage, and for transmitting a predetermined signal; a first power supply operating during both a standby state and a power-ON state, and acting as a supply source of a first predetermined voltage; a second power supply operating during the power-ON state and not operating during the standby state, and acting as a second supply source of a second predetermined voltage, which is a predetermined value higher than the first predetermined voltage; a pull-up voltage supply circuit, connected with the first power supply and the second power supply, for supplying the pull-up voltage; a first device connected with the pull-up voltage supply circuit by the bus; a second device connected with the pull-up voltage supply circuit and the first device by the bus; the pull-up voltage supply circuit supplies the pull-up voltage equal to the first predetermined voltage to the first device via the bus during the standby state, while supplying the pull-up voltage equal to the second predetermined voltage to the first device and the second device via the bus during the power-ON state; and the first device is driven by the first power supply, and capable of performing a communication via the bus in the condition in which the pull-up voltage is equal to either of the first predetermined voltage and the second predetermined voltage, the second device is driven by the second power supply, and capable of performing a communication via the bus in the condition in which the pull-up voltage is equal to the second predetermined voltage, wherein the pull-up voltage supply circuit includes the first power supply supplies a first power supply voltage obtained by adding a voltage corresponding to a forward voltage drop of the first and third diodes to the first predetermined voltage, and the second power supply supplies a second power supply voltage obtained by adding a voltage corresponding to a forward voltage drop of the second and fourth diodes to the second predetermined voltage.