Voltage reference with temperature-selective second-order temperature compensation

1. A method for producing a compensated voltage reference, the method comprising:

operating a voltage reference circuit comprising a first transistor configured to drive a first reference current through a first current path, a second transistor configured to drive a second reference current through a second current path, and an amplifier configured to produce a reference voltage based on a difference between currents present on the first current path and the second current path;

activating a first compensation circuit when an operating temperature is less than or equal to a first temperature threshold, wherein the first compensation circuit is configured to extract a first compensation current from the first current path;

deactivating the first compensation circuit when the operating temperature is greater than the first temperature threshold;

activating a second compensation circuit when the operating temperature is greater than or equal to a second temperature threshold, wherein the second compensation circuit is configured to extract a second compensation current from the first current path, wherein the second temperature threshold is greater than the first temperature threshold; and

deactivating the second compensation circuit when the operating temperature is less than the second temperature threshold.

2. The method of claim 1 , wherein a magnitude of the first compensation current is proportional to the operating temperature, and wherein a magnitude of the second compensation current is proportional to the operating temperature.

3. The method of claim 1 , wherein the first temperature threshold is less than 27 degrees Celsius, and wherein the second temperature threshold is greater than 27 degrees Celsius.

4. The method of claim 3 , wherein the first temperature threshold is between 10 degrees Celsius and 20 degrees Celsius, and wherein the second temperature threshold is between 60 degrees Celsius and 70 degrees Celsius.

5. The method of claim 1 , wherein deactivating the first compensation circuit further includes extracting a control current from a reference current path of a current mirror included in the first compensation circuit.

6. The method of claim 1 , further comprising:

extracting a third compensation current from the first current path when the operating temperature is greater than the first temperature threshold and less than the second temperature threshold.

7. A system for producing a compensated voltage reference, comprising:

a voltage reference circuit including:

a first transistor configured to drive a first reference current through a first current path,

a second transistor configured to drive a second reference current through a second current path, and

an amplifier having a non-inverting input coupled to the first current path and an inverting input coupled to the second current path, wherein the amplifier is configured to produce a reference voltage based on a difference between currents present on the first current path and the second current path; and

a compensation controller including:

a first compensation circuit configured to extract a first compensation current from the first current path, and

a second compensation circuit configured to extract a second compensation current from the first current path,

wherein the compensation controller is configured to:

activate the first compensation circuit when an operating temperature is less than or equal to a first temperature threshold,

deactivate the first compensation circuit when the operating temperature is greater than the first temperature threshold,

activate the second compensation circuit when the operating temperature is greater than or equal to a second temperature threshold, wherein the second temperature threshold is greater than the first temperature threshold, and

deactivate the second compensation circuit when the operating temperature is less than the second temperature threshold.

8. The system of claim 7 , wherein a magnitude of the first compensation current is proportional to the operating temperature, and wherein a magnitude of the second compensation current is proportional to the operating temperature.

9. The system of claim 7 , wherein the first temperature threshold is less than 27 degrees Celsius, and wherein the second temperature threshold is greater than 27 degrees Celsius.

10. The system of claim 7 , wherein the first compensation circuit includes a current mirror, and wherein, to deactivate the first compensation circuit, the compensation controller is further configured to extract a control current from a reference current path of the current mirror.

11. The system of claim 10 , wherein the first compensation circuit further includes:

a current mirror defining a reference current path and a mirror current path, wherein the current mirror is configured to extract the first compensation current from the first current path through mirror current path,

a third transistor configured to supply current to the reference current path, wherein the current supplied by the third transistor is inversely related to the operating temperature,

a fourth transistor configured to supply current, wherein the current supplied by the fourth transistor is inversely related to the current supplied by the third transistor,

a fifth transistor configured to receive the current supplied by the fourth transistor, and

a sixth transistor configured to activate when current supplied by the fourth transistor is greater than a current capacity of the fifth transistor, wherein, when active, the sixth transistor is configured to extract substantially all the current supplied by the third transistor to the reference current path.

12. The system of claim 7 , wherein a collector of the first transistor is coupled to the non-inverting input of the amplifier, wherein a collector of the second transistor is coupled to the inverting input of the amplifier, wherein an output of the amplifier is coupled to a base of the first transistor and a base of the second transistor, wherein the voltage reference circuit further includes:

a first resistor coupled between an emitter of the first transistor and an emitter of the second transistor, and

a second resistor coupled between the emitter of the second transistor and a reference terminal.

13. The system of claim 7 , wherein the compensation controller is further configured to extract a third compensation current from the first current path when the operating temperature is greater than the first temperature threshold and less than the second temperature threshold.

14. The system of claim 7 , wherein the first compensation circuit does not extract the first compensation current from the first current path when the operating temperature is greater than the first temperature threshold.

15. An apparatus for producing a compensated voltage reference, comprising:

means for driving a first reference current through a first current path;

means for driving a second reference current through a second current path;

means for producing a reference voltage based on a difference between currents present on the first current path and the second current path;

means for extracting a first compensation current from the first current path;

means for extracting a second compensation current from the first current path;

means for activating the means for extracting the first compensation current when an operating temperature is less than or equal to a first temperature threshold;

means for deactivating the means for extracting the first compensation current when the operating temperature is greater than the first temperature threshold;

means for activating the means for extracting the second compensation current when the operating temperature is greater than or equal to a second temperature threshold, wherein the second temperature threshold is greater than the first temperature threshold; and

means for deactivating the means for extracting the second compensation current when the operating temperature is less than the second temperature threshold.

16. The apparatus of claim 15 , wherein a magnitude of the first compensation current is proportional to the operating temperature, and wherein a magnitude of the second compensation current is proportional to the operating temperature.

17. The apparatus of claim 15 , wherein the first temperature threshold is less than 27 degrees Celsius, and wherein the second temperature threshold is greater than 27 degrees Celsius.

18. The apparatus of claim 17 , wherein the first temperature threshold is between 10 degrees Celsius and 20 degrees Celsius, and wherein the second temperature threshold is between 60 degrees Celsius and 70 degrees Celsius.

19. The apparatus of claim 15 , wherein the means for deactivating the means for extracting the first compensation current is further configured to extract a control current from a reference current path of a current mirror included in the means for extracting the first compensation current.

20. The apparatus of claim 15 , further comprising means for extracting a third compensation current from the first current path when the operating temperature is greater than the first temperature threshold and less than the second temperature threshold.