A driver circuit including a pre-driver B 1 that operates by receiving operating power from a first power supply VDDI, and a main-driver B 2 that receives operating power from a second power supply VDDE, amplifies an output signal from the pre-driver B 1 , and outputs the amplified signal. It also includes a first switch B 4 between the first power supply VDDI and the pre-driver B 1 . It also includes a second switch B 5 between the second power supply VDDE and the main-driver B 2 . A overvoltage protection sequence circuit B 3 controls the On/Off states of the first switch B 4 and the second switch B 5 to controls the On/Off order of the pre-driver B 1 and the main-driver B 2 . By doing so, the overvoltage protection sequence circuit B 3 prevent an overvoltage from being applied to the driver circuit, especially to the main-driver B 2.
1. A driver circuit comprising:
a pre-driver that operates by receiving operating power from a first power supply;
a main-driver that receives operating power from a second power supply, and amplifies an output signal from the pre-driver and outputs the amplified signal;
a first switch provided between the first power supply and the pre-driver;
a second switch provided between the second power supply and the main-driver; and
an overvoltage protection sequence circuit that receives operating power from the first and second power supplies and performs On/Off control of the first and second switch.
2. The driver circuit according to claim 1 , wherein when the first power supply is an Off-state and only the second power supply is an On-state, the overvoltage protection sequence circuit disconnects the main-driver from the second power supply by turning off the second switch.
3. The driver circuit according to claim 1 , wherein
a mode switching signal used to perform switching between an enable mode and a power-down mode is input to the overvoltage protection sequence circuit from an external control terminal, and
when the mode switching signal is in a power-down mode, the overvoltage protection sequence circuit maintains the second switch in an Off-state.
4. The driver circuit according to claim 1 , wherein
a voltage monitoring signal used to monitor an operating voltage of the main-driver is input to the overvoltage protection sequence circuit, and a mode switching signal used to perform switching between an enable mode and a power-down mode is also input to the overvoltage protection sequence circuit from an external control terminal, and
the overvoltage protection sequence circuit disconnects the pre-driver from the first power supply by turning off the first switch in response to a situation in which the voltage monitoring signal of the main-driver is at a low level and the mode switching signal is in a power-down mode.
5. The driver circuit according to claim 1 , wherein
a mode switching signal used to perform switching between an enable mode and a power-down mode is input to the overvoltage protection sequence circuit from an external control terminal, and
the overvoltage protection sequence circuit turns on the first switch in response to a situation in which the mode switching signal is in an enable mode.
6. The driver circuit according to claim 1 , wherein
a mode switching signal used to perform switching between an enable mode and a power-down mode is input to the overvoltage protection sequence circuit from an external control terminal, and
the overvoltage protection sequence circuit turns on a constant current source of the pre-driver and the main-driver and disengages clamping, with which an output line of the pre-driver is grounded, in response to a situation in which the mode switching signal is in an enable mode.
7. The driver circuit according to claim 1 , wherein
a mode switching signal used to perform switching between an enable mode and a power-down mode is input to the overvoltage protection sequence circuit from an external control terminal, and
the overvoltage protection sequence circuit turns on the second switch when the first power supply is an On-state and the mode switching signal is in an enable mode.
8. The driver circuit according to claim 1 , wherein the overvoltage protection sequence circuit turns on the first switch first, and then turns on the second switch.
9. The driver circuit according to claim 1 , wherein
even if the mode switching signal is changed from an enable mode to a power-down mode, the overvoltage protection sequence circuit maintains the first switch in an On-state when the voltage monitor signal from the main-driver is at a H-level, and
the overvoltage protection sequence circuit turns off the second switch first, and then turns off the first switch.
10. The driver circuit according to claim 1 , wherein the second power supply supplies a higher voltage than the first power supply.
11. The driver circuit according to claim 1 , wherein an output portion of the main-driver is formed by low-withstand-voltage transistors.