Internally generated DFT stepped hysteresis sweep for electrostatic MEMS
The present invention generally relates to a mechanism for testing a MEMS hysteresis. A power management circuit may be coupled to the electrodes that cause the movable plate that is disposed between the electrodes in a MEMS device to move. The power management circuit may utilize a charge pump, a comparator and a resistor ladder.
1. A MEMS DVC, comprising:
at least one MEMS device, the MEMS device comprising a movable plate, an RF electrode, one or more pull-down electrodes and one or more pull-up electrodes;
a first switch coupled to either the one or more pull-down electrodes of the MEMS device or the one or more pull-up electrodes of the MEMS device, wherein the first switch is additionally coupled to ground;
a second switch coupled to either the one or more pull-down electrodes of the MEMS device or the one or more pull-up electrodes of the MEMS device; and
a power management system coupled to the second switch, wherein the at least one MEMS device, the first switch, the second switch and the power management system are all disposed in a single package.
2. The MEMS DVC of claim 1 , wherein the single package comprises a first semiconductor chip having the power management system disposed thereon and a second semiconductor chip having the MEMS device disposed thereon.
3. The MEMS DVC of claim 1 , wherein the power management system comprises:
a charge pump; and
a resistive ladder coupled between the charge pump and the second switch.
4. The MEMS DVC of claim 3 , wherein the power management system further comprises a comparator coupled between the charge pump and the resistive ladder.
5. The MEMS DVC of claim 4 , wherein the power management system further comprises a gate coupled between the comparator and the charge pump.
6. The MEMS DVC of claim 5 , wherein the comparator is coupled to a bandgap voltage node on the semiconductor chip.
7. The MEMS DVC of claim 6 , wherein the gate is coupled to a clock voltage node on the semiconductor chip.
8. The MEMS DVC of claim 7 , wherein the resistive ladder comprises a plurality of resistors.
9. The MEMS DVC of claim 8 , further comprising a plurality of address bits coupled to the resistive ladder.
10. The MEMS DVC of claim 9 , wherein the second switch is coupled to the one or more pull-down electrodes.
11. The MEMS DVC of claim 9 , wherein the second switch is coupled to the one or more pull-up electrodes.
12. The MEMS DVC of claim 1 , wherein the second switch is coupled to the one or more pull-down electrodes.
13. The MEMS DVC of claim 1 , wherein the second switch is coupled to the one or more pull-up electrodes.
14. The MEMS DVC of claim 1 , wherein the power management system includes a resistive ladder having a plurality of resistors.
15. The MEMS DVC of claim 14 , wherein the resistive ladder is coupled to one or more address bits.
16. The MEMS DVC of claim 15 , wherein the plurality of resistors are coupled together in series.
17. The MEMS DVC of claim 1 , wherein the first switch is coupled to the one or more pull-down electrodes and the second switch is coupled to the one or more pull-down electrodes, the MEMS DVC further comprising:
a third switch coupled to the one or more pull-up electrodes and to ground; and
a fourth switch coupled to the one or more pull-up electrodes and to the power management system.
18. The MEMS DVC of claim 17 , wherein the power management system includes a resistive ladder having a plurality of resistors.
19. The MEMS DVC of claim 18 , wherein the resistive ladder is coupled to one or more address bits.
20. The MEMS DVC of claim 1 , wherein the MEMS DVC includes a MIM capacitor.
21. A method of testing the MEMS DVC of claim 1 , the method comprising:
applying a first voltage to the one or more pull-down electrodes of the MEMS device to move the movable plate from a free standing state capacitance to an increased capacitance state;
measuring a capacitance of the MEMS device;
applying a second voltage to the one or more pull-down electrodes of the MEMS device;
measuring the capacitance of the MEMS device;
detecting the capacitance of the MEMS device equals a maximum capacitance of the MEMS device;
removing the second voltage from the one or more pull-down electrodes of the MEMS device;
measuring the capacitance of the MEMS device;
removing the first voltage from the one or more pull-down electrodes of the MEMS device;
measuring the capacitance of the MEMS device; and
detecting the capacitance of the MEMS device is equal to the free standing state capacitance.
22. A method of testing the MEMS DVC of claim 1 , the method comprising:
applying a first voltage to the one or more pull-up electrodes of the MEMS device to move the movable plate from a free standing state capacitance to a decreased capacitance state;
measuring a capacitance of the MEMS device;
applying a second voltage to the one or more pull-up electrodes of the MEMS device;
measuring the capacitance of the MEMS device;
detecting the capacitance of the MEMS device equals a minimum capacitance of the MEMS device;
removing the second voltage from the one or more pull-up electrodes of the MEMS device;
measuring the capacitance of the MEMS device;
removing the first voltage from the one or more pull-up electrodes of the MEMS device;
measuring the capacitance of the MEMS device; and
detecting the capacitance of the MEMS device is equal to the free standing state capacitance.