Using parametric measurement units as a source of power for a device under test

1. An apparatus for applying power to a device under test, comprising:

plural parametric measurement units, the plural parametric measurement units comprising substantially same circuitry, each of the plural parametric measurement units being configurable to operate as a current source to power the device under test or as a sensing device, the plural parametric measurement units comprising:

a first parametric measurement unit configured to sense a voltage at the device, the first parametric measurement unit comprising a sense path that taps a voltage at a power pin of the device under test; and

at least two additional parametric measurement units configured to operate as a current source, the at least two additional parametric measurement units being operable in a first mode to provide regulated output current and in a second mode to provide regulated output voltage, the at least two additional parametric measurement units for receiving voltage via the first parametric measurement unit and for providing output current to the power pin of the device under test, the output current being provided based on the voltage received via the first parametric measurement unit.

2. The apparatus of claim 1 , wherein the at least two additional parametric measurement units comprise:

a second parametric measurement unit configured to operate as a current source, the second parametric measurement unit comprising a second driver that outputs current to the power pin of the device under test, the second driver receiving voltage via the first parametric measurement unit; and

a third parametric measurement unit configured to operate as a current source, the third parametric measurement unit comprising a third driver that outputs current to the power pin of the device under test, the third driver receiving voltage via the first parametric measurement unit.

3. The apparatus of claim 2 , wherein the sense path of the first parametric measurement unit leads to inputs of the second and third drivers.

4. The apparatus of claim 2 , wherein the at least two additional parametric measurement units comprise:

a fourth parametric measurement unit configured to operate as a current source, the fourth parametric measurement unit comprising a fourth driver that outputs current to the power pin of the device under test, the fourth driver receiving, as inputs, both an external voltage and a voltage received via the first parametric measurement unit.

5. The apparatus of claim 2 , wherein the second parametric measurement unit and the third parametric measurement unit each comprise a feedback path, and

wherein a feedback path of the second parametric measurement unit provides an input to the second driver, and a feedback path of the third parametric measurement unit provides an input to the third driver.

6. The apparatus of claim 5 , wherein the feedback path of the second parametric measurement unit taps a voltage between the device under test and the second driver; and

wherein the feedback path of the third parametric measurement unit taps a voltage between the device under test and the third driver.

7. The apparatus of claim 1 , wherein the first parametric measurement unit is configured to sense a voltage at the device by disabling functionality in the first parametric measurement unit that enables the first parametric measurement unit to operate as a current source.

8. The apparatus of claim 7 , wherein the functionality in the first parametric measurement unit that enables the first parametric measurement unit to operate as a current source comprises a driver; and

wherein disabling the driver comprises tri-stating the driver.

9. The apparatus of claim 1 , wherein the apparatus comprises automatic test equipment for testing functions performed by the device under test; and

wherein the automatic test equipment does not include a power supply other than the plural parametric measurement units for powering the device under test.

10. The apparatus of claim 1 , further comprising:

a common signal path electrically connecting the at least two additional parametric measurement units, the at least two additional parametric measurement units being configured to receive a signal via the common signal path, the signal for use in controlling current outputs of the at least two additional parametric measurement units so that the current outputs are at predefined values.

11. The apparatus of claim 10 , wherein the current outputs have same values.

12. The apparatus of claim 10 , wherein the first parametric measurement unit is electrically connected to the common signal path, and wherein the first parametric measurement unit provides the signal to the common signal path.

13. The apparatus of claim 12 , wherein the signal is based on the voltage at the power pin of the device.

14. The apparatus of claim 1 , wherein the at least two additional parametric measurement units each comprises a voltage sense path that is disabled when the at least two additional parametric measurement units unit provide current to a power pin of the device.

15. A method of providing current to a device under test, comprising:

configuring a first parametric measurement unit to sense a first voltage at a power pin of the device under test through an output path of the first parametric measurement unit;

sensing an output current provided to a device under test by a second parametric measurement unit, the second parametric measurement unit generating the output current based on the first voltage;

providing a voltage that corresponds to the output current as input to plural parametric measurement units;

outputting current from each of the plural parametric measurement units, current from each parametric measurement unit being based on the voltage; and

combining currents from the plural parametric measurement units at the power pin of the device under test to thereby provide power to the device under test.

16. The method of claim 15 , wherein the plural parametric measurement units are different parametric measurement units than the first and second parametric measurement units.

17. An apparatus that is configurable to operate as a current source to power a device under test, comprising:

a first parametric measurement unit that is operable in a first mode to provide regulated output current and in a second mode to provide regulated output voltage, the first parametric measurement unit being configured to provide current to a power pin of the device in the first mode or the second mode;

a second parametric measurement unit that is operable in the first mode to provide regulated output current and in the second mode to provide regulated output voltage, the second parametric measurement unit being configured to provide current to the power pin of the device in the first mode or the second mode so as to augment the current from the first parametric measurement unit at the power pin of the device with the current from the second parametric measurement unit; and

a third parametric measurement unit configured to sense a voltage at the device, the voltage being input to the first parametric measurement unit.

18. The apparatus of claim 17 , wherein the apparatus comprises automatic test equipment for testing functions performed by the device under test; and

wherein the automatic test equipment does not include a power supply other than the first, second and third parametric measurement units for powering the device under test.

19. The apparatus of claim 17 , further comprising:

a fourth parametric measurement unit configured to provide current to the device so as to augment the current from the first parametric measurement unit and the second parametric measurement unit at the power pin of the device with the current from the fourth parametric measurement unit.