Smooth vi mode crossover method at compliance limit threshold
View Patent ↗Source measure units may operate as a voltage/current (V/I) source for a load, such as a device under test (DUT). Source measure units having a voltage controlled mode and a current controlled mode are described. The source measure units may have a suitable configuration to transition between the voltage controlled mode and current controlled mode in a smooth manner, and may be operated accordingly.
1. A method of operating a source measure unit (SMU) configured to couple to a load, the SMU operating in a plurality of modes including a voltage-controlled mode and a current-controlled mode, the method comprising:
generating a control signal to apply to a control circuit of the SMU when switching between the plurality of modes, wherein generating the control signal comprises combining a first signal, a second signal and a third signal,
wherein the first signal is indicative of a voltage error of a voltage across the load relative to a target voltage,
wherein the second signal is indicative of a first current error of a current through the load relative to an upper current threshold, and
wherein the third signal is indicative of a second current error of the current through the load relative to a lower current threshold.
2. The method of claim 1 , wherein the first signal is indicative of a voltage error of the voltage detected across the load relative to a target voltage of a drive signal of the SMU.
3. The method of claim 1 , wherein combining the first signal, the second signal and the third signal comprises generating a weighted combination of the first signal and the second signal.
4. The method of claim 1 , wherein combining the first signal, the second signal and the third signal comprises generating a weighted combination of the first signal, the second signal, and the third signal.
5. The method of claim 4 , wherein a first weighting factor is associated with the first signal, a second weighting factor is associated with the second signal, and a third weighting factor is associated with the third signal, and wherein a sum of the first weighting factor, the second weighting factor, and the third weighting factor is one.
6. The method of claim 5 , wherein the first weighting factor and/or the second weighting factor and/or the third weighting factor is variable.
7. The method of claim 6 , wherein the first weighting factor and/or second weighting factor and/or third weighting factor is generated by a function.
8. The method of claim 7 , wherein the function is dependent on voltage.
9. The method of claim 8 , wherein the function is dependent on voltage error.
10. The method of claim 7 , wherein the function is dependent on current.
11. The method of claim 10 , wherein the function is dependent on current error.
12. The method of claim 1 , wherein the load is a device under test (DUT).
13. A method of operating a source measure unit (SMU) configured to couple to a load, the SMU operating in a plurality of modes including a voltage-controlled mode and a current-controlled mode, the method comprising:
generating a control signal to apply to a control circuit of the SMU when switching between the plurality of modes, wherein generating the control signal comprises combining a first signal, a second signal and a third signal,
wherein the first signal is indicative of a first voltage error of a voltage across the load relative to an upper voltage threshold,
wherein the second signal is indicative of a current error of a current through the load relative to a target current, and
wherein the third signal is indicative of a second voltage error of the voltage across the load relative to a lower voltage threshold.
14. The method of claim 13 , wherein combining the first signal, the second signal and the third signal comprises generating a weighted combination of the first signal, the second signal, and the third signal.
15. The method of claim 14 , wherein a first weighting factor is associated with the first signal, a second weighting factor is associated with the second signal, and a third weighting factor is associated with the third signal, and wherein a sum of the first weighting factor, the second weighting factor, and the third weighting factor is one.
16. The method of claim 15 , wherein the first weighting factor and/or the second weighting factor and/or the third weighting factor is variable.
17. The method of claim 16 , wherein the first weighting factor and/or second weighting factor and/or third weighting factor is generated by a function.
18. The method of claim 17 , wherein the function is dependent on voltage.
19. The method of claim 18 , wherein the function is dependent on voltage error.
20. The method of claim 17 , wherein the function is dependent on current.
21. The method of claim 20 , wherein the function is dependent on current error.
22. A source measure unit (SMU) configured to operate in a plurality of modes including a voltage-controlled mode and a current-controlled mode, the SMU comprising:
combination circuitry configured to generate, when the SMU transitions between the voltage-controlled mode and the current controlled mode, a control signal to provide to a control circuit of the SMU, the control signal being generated by combining a first signal, a second signal and a third signal,
wherein the first signal is indicative of a voltage error of a voltage relative to a target voltage,
wherein the second signal is indicative of a first current error of a current relative to an upper current threshold, and
wherein the third signal is indicative of a second current error of the current relative to a lower current threshold.
23. The SMU of claim 22 , wherein the combination circuitry comprises weighting circuitry configured to form a weighted combination of the first signal, the second signal, and the third signal.
24. A source measure unit (SMU) configured to operate in a plurality of modes including a voltage-controlled mode and a current-controlled mode, the SMU comprising:
combination circuitry configured to generate, when the SMU transitions between the voltage-controlled mode and the current controlled mode, a control signal to provide to a control circuit of the SMU, the control signal being generated by combining a first signal, a second signal and a third signal,
wherein the first signal is indicative of a first voltage error of a voltage relative to an upper voltage threshold,
wherein the second signal is indicative of a current error of a current relative to a target current, and
wherein the third signal is indicative of a second voltage error of the voltage relative to a lower voltage threshold.
25. The SMU of claim 24 , wherein the combination circuitry comprises weighting circuitry configured to formed a weighted combination of the first signal, the second signal, and the third signal.