Bus driver including control circuit for overvoltage protection
View Patent ↗A bus driver device is provided with a bus driver circuit connected to a bus line and a overvoltage protection section connected between the bus line and a power supply line. The overvoltage protection section has an overvoltage protection function for the bus line. Further, the bus driver device is provided with a switching circuit for on/off-controlling the overvoltage protection function based on a voltage of the bus line and a voltage of the power supply wiring.
1. A bus driver device, comprising:
a bus driver circuit connected to a bus line;
a power supply wiring;
an overvoltage protection section connected between the bus line and the power supply wiring, which has an overvoltage protection function for the bus line; and
a switching circuit for on/off-controlling the overvoltage protection function based on a voltage of the bus line and a voltage of the power supply wiring,
wherein the switching circuit comprises;
a first transistor connected between the power supply wiring and the overvoltage protection section; and
a control circuit for on/off-controlling the first transistor based on the voltage on the bus line, and
wherein the overvoltage protection section comprises:
a second transistor connected between the bus line and the first transistor, which has a back gate; and
a third transistor connected between the back gate of the second transistor and the power supply wiring.
2. The bus driver device according to claim 1 , wherein the control circuit comprises:
a voltage detection section for detecting a voltage on the power supply wiring and the voltage on the bus line; and
an inverter for on/off-controlling the first transistor based on a detection result obtained by the voltage detection section.
3. The bus driver device according to claim 1 , wherein the control circuit further on/off-controls the third transistor based on the voltage on the bus line.
4. The bus driver device according to claim 1 , further comprising a ground wiring,
wherein the overvoltage protection section further comprises a fourth transistor connected between the bus line and the ground wiring.
5. A bus driver device, comprising:
a bus driver circuit connected to a bus line;
a power supply wiring;
an overvoltage protection section connected between the bus line and the power supply wiring, which has an overvoltage protection function for the bus line; and
a switching circuit for on/off-controlling the overvoltage protection function based on a voltage of the bus line and a voltage of the power supply wiring,
wherein switching circuit comprises:
a first transistor connected between the power supply wiring and the overvoltage protection section; and
a control circuit for on/off-controlling the first transistor based on the voltage on the bus line,
the bus driver device further comprising a ground wiring,
wherein the control circuit comprises:
a first voltage monitor section for monitoring the voltage on the bus line;
a second voltage monitor section connected between the first voltage monitor section and the ground wiring, for monitoring a voltage on the power supply wiring; and
an inverter for on/off-controlling the first transistor based on monitor results obtained by the first voltage monitor section and the second voltage monitor section.
6. A bus driver device comprising:
a bus driver circuit connected to a bus line;
a power supply wiring;
an overvoltage protection section connected between the bus line and the power supply wiring, which has an overvoltage protection function for the bus line; and
a switching circuit for on/off-controlling the overvoltage protection function based on a voltage of the bus line and a voltage of the power supply wiring,
wherein the switching circuit comprises:
a first transistor connected between the power supply wiring and the overvoltage protection section; and
a control circuit for on/off-controlling the first transistor based on the voltage on the bus line, and
wherein the control circuit comprises:
a voltage detection section for detecting a voltage on the power supply wiring and the voltage on the bus line;
an inverter for on/off-controlling the first transistor based on a detection result obtained by the voltage detection section; and
a resistor connected between the bus line and the inverter.