Bidirectional switch and switch circuit using the bidirectional switch

1. A switch circuit to be mounted in a mobile device having a shared terminal that allows insertion of a terminal of a USB cable or insertion of a terminal of a cable dedicated to the transmission of audio signals in a shared manner, comprising:

a USB switch connected between the shared terminal and a USB driver within the mobile device;

an audio switch connected to the shared terminal and connected in parallel with the USB switch;

a second switch connected between the audio switch and a first audio circuit within the mobile device; and

a third switch connected between the first audio switch and a second audio circuit within the mobile device and connected in parallel with the second switch, wherein

each of the USB switch, the audio switch, the second switch, and the third switch is a bidirectional switch constructed by using a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), and a source terminal and a backgate terminal of the MOSFET are connected via a transfer gate.

2. The switch circuit according to claim 1 , wherein

the bidirectional switch includes a switch connected between a connection point of the backgate terminal and the transfer gate and a ground potential or supply potential, and when the backgate of the MOSFET is turned off, the switch is controlled to be on and the potential of the backgate terminal of the MOSFET is controlled to be the ground potential or supply potential.

3. A multi-mode switch circuit, comprising:

a first shared bidirectional port;

a first bidirectional switch having a first terminal connected to the first shared bidirectional port, a second terminal, and a control terminal;

a second bidirectional switch having a first terminal connected to the first shared bidirectional port, a second terminal, and a control terminal;

a third switch having an input terminal connected to a first terminal of the multi-mode switch circuit, a second terminal connected to the second terminal of the first bidirectional switch, and a control terminal;

a fourth switch having a first terminal having an input terminal connected to the second terminal of the second bidirectional switch, and a second terminal connected to an output terminal of the multi-mode switch circuit; and

a controller coupled to the control terminals of the first and second bidirectional switches and the third and fourth switches, for enabling only the first bidirectional switch in a first mode, for enabling only the second bidirectional switch and the third switch in a second mode, and for enabling only the second bidirectional switch and the fourth switch in a third mode.

4. The multi-mode switch circuit of claim 3 , wherein:

the first mode comprises a universal serial bus (USB) mode, the second mode comprises an audio headphone mode, and the third mode comprises an audio microphone mode.

5. The multi-mode switch circuit of claim 3 , wherein each of the first and second bidirectional switches comprises:

a metal-oxide-semiconductor field-effect transistor (MOSFET), wherein a source terminal and a backgate terminal of the MOSFET are connected to each other via a transfer gate.

6. The multi-mode switch circuit of claim 5 , wherein the transfer gate comprises:

a first transistor of a first conductivity type having a first terminal coupled to the source terminal of the MOSFET, a gate for receiving a control signal, and a second terminal coupled to the backgate terminal of the MOSFET; and

a second transistor of a second conductivity type having a first terminal coupled to the source terminal of the MOSFET, a gate for receiving a complement of the control signal, and a second terminal coupled to the backgate terminal of the MOSFET.

7. The multi-mode switch circuit of claim 5 , wherein each of the first and second bidirectional switches further comprises:

a second MOSFET connected between a connection point of the backgate terminal and the transfer gate and one of a ground potential and a supply potential, wherein when the backgate of the MOSFET is turned off, the second MOSFET is controlled to be on and the potential of the backgate terminal of the MOSFET is controlled to be the one of the ground potential and the supply potential.

8. The multi-mode switch circuit of claim 3 , wherein the first shared bidirectional port, the first bidirectional switch, the second bidirectional switch, the third switch, and the fourth switch are combined on a single integrated circuit.

9. The multi-mode switch circuit of claim 3 , further comprising:

a second shared bidirectional port of the multi-mode switch circuit;

a fifth switch having a first terminal for conducting a power supply voltage, a second terminal coupled to the second shared bidirectional port of the multi-mode switch circuit, and a control terminal; and

a sixth switch having a first terminal connected to the second shared bidirectional port of the multi-mode switch circuit, a second terminal coupled to the second shared bidirectional port of the multi-mode switch circuit, and a control terminal, wherein the controller enables the fifth switch in the first mode, and the sixth switch in a fourth mode.

10. A multi-mode switch apparatus comprising a switch circuit, the switch circuit comprising:

a primary hierarchical level comprising:

a first bidirectional switch having a first terminal, a second terminal, and a control terminal; and

a second bidirectional switch having a first terminal, a second terminal, and a control terminal,

a second hierarchical level comprising:

a third switch having a first terminal, a second terminal coupled to the first terminal of the second bidirectional switch, and a control terminal; and

a fourth switch having a first terminal, a second terminal coupled to the first terminal of the second bidirectional switch, and a control terminal, and

a controller for enabling only the first bidirectional switch in a first mode, only the second bidirectional switch and the third switch in a second mode, and only the second bidirectional switch and the fourth switch in a third mode.

11. The multi-mode switch apparatus of claim 10 , wherein:

the first mode comprises a universal serial bus (USB) mode, the second mode comprises an audio headphone mode, and the third mode comprises an audio microphone mode.

12. The multi-mode switch apparatus of claim 10 , wherein each of the first and second bidirectional switches comprises:

a metal-oxide-semiconductor field-effect transistor (MOSFET), wherein a first terminal and a backgate terminal of the MOSFET are seletively coupled to each other via a transfer gate.

13. The multi-mode switch apparatus of claim 12 , wherein the MOSFET comprises an n-channel MOSFET.

14. The multi-mode switch apparatus of claim 12 , wherein the transfer gate comprises:

a first transistor of a first conductivity type having a first terminal coupled to the first terminal of the MOSFET, a gate for receiving a control signal, and a second terminal coupled to the backgate terminal of the MOSFET; and

a second transistor of a second conductivity type having a first terminal coupled to the first terminal of the MOSFET, a gate for receiving a complement of the control signal, and a second terminal coupled to the backgate terminal of the MOSFET.

15. The multi-mode switch apparatus of claim 14 , wherein the first conductivity type comprises n-channel, and the second conductivity type comprises p-channel.

16. The multi-mode switch apparatus of claim 12 , wherein each of the first and second bidirectional switches further comprises:

a switch connected between a connection point of the backgate terminal and the transfer gate and one of a ground potential and a supply potential, wherein when the backgate of the MOSFET is turned off, the switch is controlled to be on and the potential of the backgate terminal of the MOSFET is controlled to be the one of the ground potential and the supply potential.

17. The multi-mode switch apparatus of claim 10 , wherein the first bidirectional switch, the second bidirectional switch, the third switch, the fourth switch, and the controller are combined on a single integrated circuit.

18. The multi-mode switch apparatus of claim 10 , further comprising:

a second shared bidirectional port of the switch circuit;

a fifth switch having a first terminal for conducting a power supply voltage, a second terminal coupled to the second shared bidirectional port of the switch circuit, and a control terminal; and

a sixth switch having a first terminal connected to the second shared bidirectional port of the switch circuit, a second terminal coupled to the second shared bidirectional port of the switch circuit, and a control terminal, wherein the controller enables the fifth switch in the first mode, and the sixth switch in a fourth mode.

19. The multi-mode switch apparatus of claim 10 , further comprising:

a common connector coupled to the second terminals of each of the first and second bidirectional switches, having a plurality of external bidirectional terminals adapted to interface to a selected one of a first cable of a first type and a second cable of a second type.

20. The multi-mode switch apparatus of claim 19 , wherein the first type comprises universal serial bus (USB), and the second type comprises audio.