Internal reference voltage generation for integrated circuit testing

1. An integrated circuit, comprising:

a first voltage generator on the integrated circuit to generate a first voltage that is adjustable based on a supply voltage powering the integrated circuit, wherein the first voltage generator comprises a variable voltage divider which provides a selectable output voltage as the first voltage;

a second voltage generator on the integrated circuit to generate a second voltage;

a third voltage generator on the integrated circuit to generate one or more internal voltages based on a reference voltage; and

control circuitry to select the first voltage for use as the reference voltage in a test mode and to select the second voltage for use as the reference voltage in a non-test mode.

2. The integrated circuit of claim 1 , wherein the second voltage generator generates a second voltage that is substantially temperature independent.

3. The integrated circuit of claim 1 , wherein the second voltage generator generates a second voltage that is substantially constant over an operating range of the supply voltage.

4. The integrated circuit of claim 1 , further comprising:

memory circuitry,

wherein the third voltage generator generates one or more internal voltages for the memory circuitry based on the reference voltage.

5. The integrated circuit of claim 1 , further comprising:

adjustment circuitry to adjust the second voltage generator to provide the second voltage in a desired range.

6. A memory device, comprising:

memory circuitry;

a first voltage generator on the integrated circuit to generate a first voltage that is adjustable based on a supply voltage powering the integrated circuit, wherein the first voltage generator comprises a plurality of voltage dividers having different output voltages which are selectable to be output as the first voltage;

a second voltage generator on the integrated circuit to generate a second voltage;

a third voltage generator on the integrated circuit to generate, based on a reference voltage, one or more internal voltages to be supplied to the memory circuitry; and

control circuitry to select the first voltage as the reference voltage in a test mode and to select the second voltage as the reference voltage in a non-test mode.

7. The integrated circuit of claim 6 , wherein the second voltage generator generates a second voltage that is substantially constant over an operating range of the supply voltage.

8. The integrated circuit of claim 6 , wherein the control circuitry comprises one or more registers to select one of the plurality of voltage dividers to generate the first voltage.

9. The integrated circuit of claim 6 , wherein the second voltage generator generates a second voltage that is substantially temperature independent.

10. An integrated circuit, comprising:

means for generating one or more internal voltages based on a reference voltage;

means for generating a first voltage adjustable based on a supply voltage powering the integrated circuit, wherein the first voltage is selected as the reference voltage when the integrated circuit is in a test mode, and wherein the means for generating the first voltage comprises a variable voltage divider; and

means for generating a second voltage which is selected as the reference voltage when the integrated circuit is in a non-test mode.

11. The integrated circuit of claim 10 , further comprising:

means for adjusting the second voltage to provide the second voltage in a desired range.

12. A system, comprising:

a wafer having integrated circuits, wherein one or more of which have a first voltage generator to generate a first voltage that is adjustable based on a supply voltage, a second voltage generator to generate a second voltage, a third voltage generator to generate one or more internal voltages based on a reference voltage, and control circuitry to select the first voltage as the reference voltage in a test mode and to select the second voltage as the reference voltage in a non-test mode; and

a tester to supply one or more integrated circuits with the supply voltage, to place one or more integrated circuits in the test mode, and to test one or more integrated circuits with the first voltage selected as the reference voltage, wherein the first voltage generator comprises a variable voltage divider, and wherein the tester sets the variable voltage divider of the first voltage generator to set the first voltage.

13. The system of claim 12 , wherein the tester adjusts the supply voltage to help set the first voltage.

14. The system of claim 12 , wherein the first voltage generator comprises one or more voltage dividers, and wherein the tester selects an output from one of the one or more voltage dividers as the first voltage.

15. The system of claim 12 , wherein one or more integrated circuits have memory circuitry and wherein the third voltage generator generates one or more internal voltages for the memory circuitry based on the reference voltage.

16. The system of claim 12 , wherein one or more integrated circuits have adjustment circuitry to adjust the second voltage generator to provide the second voltage in a desired range.

17. A method for testing an integrated circuit, comprising:

supplying the integrated circuit with a supply voltage;

placing the integrated circuit in a test mode to select one of a plurality of reference voltage generators on the integrated circuit to supply to an internal voltage generator on the integrated circuit a reference voltage that is adjustable based on the supply voltage;

setting the selected reference voltage generator to set the reference voltage; and

testing the integrated circuit with the reference voltage supplied to the internal voltage generator.

18. The method of claim 17 , further comprising:

adjusting the supply voltage to set the reference voltage.

19. The method of claim 17 , wherein

the selected reference voltage generator comprises a variable voltage divider to set the reference voltage.

20. The method of claim 17 , further comprising:

adjusting a non-selected one of the reference voltage generators in response to the testing.

21. The method of claim 17 , further comprising:

placing the integrated circuit in an operational mode to select a substantially temperature independent one of the plurality of reference voltage generators on the integrated circuit to supply the reference voltage to the internal voltage generator on the integrated circuit.

22. A method for testing an integrated circuit, comprising:

supplying the integrated circuit with a supply voltage;

placing the integrated circuit in a test mode;

selecting one of a plurality of reference voltage generators on the integrated circuit to supply to an internal voltage generator on the integrated circuit a reference voltage that is adjustable based on the supply voltage, wherein the selected reference voltage generator comprises a plurality of voltage dividers coupled to the supply voltage;

selecting one of a plurality of voltage dividers to generate the reference voltage; and

testing the integrated circuit with the reference voltage supplied to the internal voltage generator.

23. The method of claim 22 , further comprising:

adjusting the supply voltage to set the reference voltage.

24. The method of claim 22 , further comprising:

adjusting a non-selected one of the reference voltage generators in response to the testing, wherein the reference voltage generated by the adjusted non-selected one of the reference voltage generators is adjusted to a desired range.

25. The method of claim 22 , further comprising:

placing the integrated circuit in an operational mode to select a substantially temperature independent one of the plurality of reference voltage generators on the integrated circuit to supply the reference voltage to the internal voltage generator on the integrated circuit.