Circuit, system and method for electrostatic discharge (ESD) protection

1. A circuit, comprising:

a discharging device between a first voltage bus and a second voltage bus;

a resistive element configured to activate the discharging device in response to a high-to-low electrostatic discharge (ESD) event during which the first voltage bus is high in potential relative to the second voltage bus; and

a bypass device connected parallel to the resistive element and configured to bypass the resistive element and activate the discharging device in response to a low-to-high ESD event during which the second voltage bus is high in potential relative to the first voltage bus, wherein the bypass device is kept off in response to the high-to-low ESD event.

2. The circuit according to claim 1 further comprising a trigger device configured to detect an ESD event, wherein the trigger device is disposed between the first voltage bus and one end of the resistive element.

3. The circuit according to claim 2 , wherein the trigger device includes a capacitor.

4. The circuit according to claim 2 , wherein the trigger device includes a transistor including a source and a drain together coupled to the first voltage bus, and including a gate coupled to the one end of the resistive element.

5. The circuit according to claim 4 , wherein the transistor includes a high-electron-mobility transistor (HEMT).

6. The circuit according to claim 2 , wherein the trigger device includes a number of transistors cascode connected.

7. The circuit according to claim 6 , wherein each of the transistors includes a HEMT.

8. The circuit according to claim 2 , wherein the discharging device includes a HEMT, the HEMT including a drain coupled to the first voltage bus, a source coupled to the second voltage bus, and a gate coupled to the one end of the resistive element.

9. The circuit according to claim 2 , wherein the bypass device includes a HEMT, the HEMT including a source coupled to the second voltage bus, a gate coupled to the second voltage bus, and a drain coupled to the one end of the resistive element.

10. A system, comprising:

an internal circuit; and

a number of devices configured to protect the internal circuit from an ESD event, each of the devices including:

a discharging device between a first voltage bus and a second voltage bus;

a resistive element configured to activate the discharging device in response to a high-to-low electrostatic discharge (ESD) event during which the first voltage bus is high in potential relative to the second voltage bus; and

a bypass device connected parallel to the resistive element and configured to bypass the resistive element and activate the discharging device in response to a low-to-high ESD event during which the second voltage bus is high in potential relative to the first voltage bus, wherein the bypass device is kept off in response to the high-to-low ESD event.

11. The system according to claim 10 , wherein a first one of the devices is disposed between the first voltage bus and the second voltage bus, the first device configured to discharge an ESD current towards one of the first voltage bus and the second voltage bus in response to an ESD event.

12. The system according to claim 10 , wherein a second one of the devices is disposed between the first voltage bus and a first conductive pin, the second device configured to discharge an ESD current towards the first voltage bus in response to an ESD event.

13. The system according to claim 12 , wherein a third one of the devices is disposed between the first conductive pin and the second voltage bus, the third device configured to discharge an ESD current towards the second voltage bus in response to an ESD event.

14. The system according to claim 10 , wherein a fourth one of the devices is disposed between the first voltage bus and a second conductive pin coupled to the internal circuit via a first internal bus, the fourth device configured to discharge an ESD current towards one of the first voltage bus and the first internal bus in response to an ESD event.

15. The system according to claim 14 , wherein a fifth one of the devices is disposed between the second voltage bus and a third conductive pin coupled to the internal circuit via a second internal bus, the fifth device configured to discharge an ESD current towards one of the second voltage bus and the second internal bus in response to an ESD event.

16. The system according to claim 10 , wherein each of devices further includes a trigger device configured to detect an ESD event, wherein the trigger device is disposed between the first voltage bus and one end of the resistive element.

17. The system according to claim 16 , wherein the discharging device includes a HEMT, the HEMT including a drain coupled to the first voltage bus, a source coupled to the second voltage bus, and a gate coupled to the one end of the resistive element.

18. The system according to claim 16 , wherein the bypass device includes a HEMT, the HEMT including a source coupled to the second voltage bus, a gate coupled to the second voltage bus, and a drain coupled to the one end of the resistive element.

19. A method, comprising:

providing a discharging device between a first voltage bus and a second voltage bus, the first voltage bus having a higher voltage level than the second voltage bus during normal operation;

activating the discharging device by a resistive element in response to an ESD event of a high-to-low (HL) type during which the first voltage bus is high in potential relative to the second voltage bus;

activating the discharging device by a bypass device in response to an ESD event of a low-to-high (LH) type during which the second voltage bus is high in potential relative to the first voltage bus, the bypass device connected parallel to the resistive element and bypassing the resistive element; and

keeping the bypass device off in response to an ESD event of the HL type.

20. The method according to claim 19 , wherein the discharging device is kept at an off state during normal operation.