Dynamic over-voltage protection scheme for integrated-circuit devices

1. An integrated circuit comprising:

a transistor device implemented in a technology having a specified operating-voltage range, the transistor device having gate, drain, source, and tub nodes, and the specified operating-voltage range having a specified maximum voltage; and

over-voltage protection circuitry adapted to apply gate and tub voltages to the gate and tub nodes, respectively, wherein:

if at least one channel voltage applied to at least one of the drain and source nodes exceeds the specified maximum voltage, then the over-voltage protection circuitry controls at least one of the gate voltage and the tub voltage to inhibit one or more adverse effects to the transistor device;

if the transistor device is to be turned on, then the over-voltage protection circuitry sets the gate voltage to the specified maximum voltage;

if the transistor device is to be turned off, then the over-voltage protection circuitry sets the gate voltage to the tub voltage;

the over-voltage protection circuitry is adapted to be programmably controlled to operate in either a normal operating mode or an over-voltage protection mode;

in the normal operating mode, the over-voltage protection circuitry sets the tub voltage to a ground voltage; and

in the over-voltage protection mode:

if the channel voltage is less than a threshold voltage, then the over-voltage protection circuitry sets the tub voltage to the ground voltage; and

if the channel voltage is greater than the threshold voltage, then the over-voltage protection circuitry sets the tub voltage to a first voltage less than the specified maximum voltage.

2. The invention of claim 1 , wherein:

the transistor device is an N-type MOSFET;

the channel voltage is a drain voltage applied to the drain node; and

the one or more adverse effects include one or more of destruction and breakdown of the transistor device.

3. The invention of claim 1 , wherein the over-voltage protection circuitry controls both the gate voltage and the tub voltage to inhibit the one or more adverse effects.

4. The invention of claim 1 , wherein the over-voltage protection circuitry is adapted to receive the channel voltage and generate both the tub voltage and the gate voltage.

5. The invention of claim 1 , wherein the first voltage is greater than or equal to a voltage difference between a maximum over-voltage and the specified maximum voltage.

6. The invention of claim 5 , wherein the first voltage is greater than the voltage difference by a selected voltage margin.

7. The invention of claim 1 , wherein the over-voltage protection circuitry is further adapted to receive a control signal that selectively enables an over-voltage protection function of the over-voltage protection circuitry.

8. The invention of claim 7 , wherein the control signal selectively disables the over-voltage protection circuitry from setting the tub voltage to anything but a ground voltage.

9. The invention of claim 1 , wherein the over-voltage protection circuitry comprises:

a tub-voltage generator adapted to receive the channel voltage and generate the tub voltage; and

a gate-voltage generator adapted to receive the tub voltage and generate the gate voltage.

10. The invention of claim 9 , wherein the tub-voltage generator is adapted to:

receive a ground voltage and a first voltage;

set the tub voltage to the ground voltage, if the channel voltage is less than a threshold voltage; and

set the tub voltage to the first voltage, if the channel voltage is greater than the threshold voltage.

11. The invention of claim 10 , wherein the first voltage is less than the specified maximum voltage.

12. The invention of claim 10 , wherein the threshold voltage is approximately equal to a difference between the specified maximum voltage and a gate voltage at which the transistor device turns on.

13. The invention of claim 10 , wherein the tub-voltage generator is further adapted to receive a control signal that selectively disables the tub-voltage generator from setting the tub voltage to anything but the ground voltage.

14. The invention of claim 9 , wherein the gate-voltage generator is adapted to:

set the gate voltage to the specified maximum voltage, if the transistor device is to be turned on; and

set the gate voltage to the tub voltage, if the transistor device is to be turned off.

15. The invention of claim 1 , wherein:

the over-voltage protection circuitry is adapted to receive the channel voltage and generate both the tub voltage and the gate voltage to inhibit the one or more adverse effects;

the first voltage is greater than a voltage difference between a maximum over-voltage and the specified maximum voltage by a selected voltage margin; and

the over-voltage protection circuitry is further adapted to receive a control signal that selectively enables the over-voltage protection function of the over-voltage protection circuitry, wherein the control signal selectively disables the tub-voltage generator from setting the tub voltage to anything but the ground voltage.

16. The invention of claim 15 , wherein the over-voltage protection circuitry comprises:

a tub-voltage generator adapted to receive the channel voltage and generate the tub voltage; and

a gate-voltage generator adapted to receive the tub voltage and generate the gate voltage, wherein:

the tub-voltage generator is adapted to:

receive the ground voltage and the first voltage;

set the tub voltage to the ground voltage, if the channel voltage is less than the threshold voltage; and

set the tub voltage to the first voltage, if the channel voltage is greater than the threshold voltage;

the threshold voltage is approximately equal to a difference between the specified maximum voltage and a gate voltage at which the transistor device turns on;

the tub-voltage generator is further adapted to receive the control signal that selectively disables the tub-voltage generator from setting the tub voltage to anything but the ground voltage; and

the gate-voltage generator is adapted to:

set the gate voltage to the specified maximum voltage, if the transistor device is to be turned on; and

set the gate voltage to the tub voltage, if the transistor device is to be turned off.

17. A method for operating a transistor device implemented in a technology having a specified operating-voltage range, the transistor device having gate, drain, source, and tub nodes, and the specified operating-voltage range having a specified maximum voltage, the method comprising applying gate, drain, source, and tub voltages to the gate, drain, source, and tub nodes, respectively, of the transistor device, wherein:

if at least one channel voltage applied to at least one of the drain and source nodes exceeds the specified maximum voltage, then at least one of the gate voltage and the tub voltage is controlled to inhibit one or more adverse effects to the transistor device;

if the transistor device is to be turned on, then the over-voltage protection circuitry sets the gate voltage to the specified maximum voltage;

if the transistor device is to be turned off, then the over-voltage protection circuitry sets the gate voltage to the tub voltage;

the over-voltage protection circuitry is adapted to be programmably controlled to operate in either a normal operating mode or an over-voltage protection mode;

in the normal operating mode, the over-voltage protection circuitry sets the tub voltage to a around voltage; and

in the over-voltage protection mode;

if the channel voltage is less than a threshold voltage, then the over-voltage protection circuitry sets the tub voltage to the ground voltage; and

if the channel voltage is greater than the threshold voltage, then the over-voltage protection circuitry sets the tub voltage to a first voltage less than the specified maximum voltage.

18. An apparatus for operating a transistor device implemented in a technology having a specified operating-voltage range, the transistor device having gate, drain, source, and tub nodes, and the specified operating-voltage range having a specified maximum voltage, the apparatus comprising:

means for applying a gate voltage to the gate node of the transistor device;

means for applying a drain voltage to the drain node of the transistor device;

means for applying a source voltage to the source node of the transistor device; and

means for applying a tub voltage to the tub node of the transistor device, wherein:

if at least one channel voltage applied to at least one of the drain and source nodes exceeds the specified maximum voltage, then at least one of the gate voltage and the tub voltage is controlled to inhibit one or more adverse effects to the transistor device;

if the transistor device is to be turned on, then the over-voltage protection circuitry sets the gate voltage to the specified maximum voltage;

if the transistor device is to be turned off, then the over-voltage protection circuitry sets the gate voltage to the tub voltage;

the over-voltage protection circuitry is adapted to be programmably controlled to operate in either a normal operating mode or an over-voltage protection mode;

in the normal operating mode, the over-voltage protection circuitry sets the tub voltage to a ground voltage; and

in the over-voltage protection mode:

if the channel voltage is less than a threshold voltage, then the over-voltage protection circuitry sets the tub voltage to the ground voltage; and

if the channel voltage is greater than the threshold voltage, then the over-voltage protection circuitry sets the tub voltage to a first voltage less than the specified maximum voltage.

19. An integrated circuit comprising:

a transistor device implemented in a technology having a specified operating-voltage range, the transistor device having gate, drain, source, and tub nodes, and the specified operating-voltage range having a specified maximum voltage;

over-voltage protection circuitry adapted to apply gate and tub voltages to the gate and tub nodes, respectively, wherein:

if at least one channel voltage applied to at least one of the drain and source nodes exceeds the specified maximum voltage, then the over-voltage protection circuitry controls at least one of the gate voltage and the tub voltage to inhibit one or more adverse effects to the transistor device;

the over-voltage protection circuitry comprises:

a tub-voltage generator adapted to receive the channel voltage and generate the tub voltage; and

a gate-voltage generator adapted to receive the tub voltage and generate the gate voltage; the tub-voltage generator is adapted to:

receive a ground voltage and a first voltage;

set the tub voltage to the ground voltage, if the channel voltage is less than a threshold voltage; and

set the tub voltage to the first voltage, if the channel voltage is greater than the threshold voltage; and

at least one of:

(i) the first voltage is less than the specified maximum voltage;

(ii) the threshold voltage is approximately equal to a difference between the specified maximum voltage and a gate voltage at which the transistor device turns on; and

(iii) the tub-voltage generator is further adapted to receive a control signal that selectively disables the tub-voltage generator from setting the tub voltage to anything but the ground voltage.

20. The invention of claim 19 , wherein the first voltage is less than the specified maximum voltage.

21. The invention of claim 19 , wherein the threshold voltage is approximately equal to the difference between the specified maximum voltage and the gate voltage at which the transistor device turns on.

22. The invention of claim 19 , wherein the tub-voltage generator is further adapted to receive the control signal that selectively disables the tub-voltage generator from setting the tub voltage to anything but the ground voltage.