Verifying correct operation of an implantable neurostimulator device using current distribution circuitry
View Patent ↗Monitoring circuitry for an implantable stimulator device is disclosed. A switching matrix allows current from a current source to be distributed to any of a plurality of electrodes. A voltage drop across the active switches in the switch matrix is monitored and is compared to an expected voltage based upon the amplitude of the current and the known on resistance of the switch. If the monitored and expected voltages differ significantly, then a failure condition can be inferred, and an appropriate action can be taken, such shutting down stimulation. Using the already-existing switches in the switching matrix in this fashion is beneficial because it allows the current through the electrodes to be monitored without providing additional structures in the therapeutic current path, which would increase complexity and add unwanted resistance.
1. An implantable stimulator device, comprising:
a plurality of electrodes;
at least one current source configured to produce at least one current;
a plurality of switches, wherein the switches are selectable to distribute the at least one current to or from one or more of the electrodes; and
monitoring circuitry configured to measure at least one voltage, each at least one voltage comprising a voltage only across one of the switches, and for determining whether a failure condition has occurred.
2. The implantable stimulator device of claim 1 , wherein the monitoring circuitry determines whether a failure condition has occurred by comparing the at least one voltage to an expected range.
3. The implantable stimulator device of claim 2 , wherein the expected range is based on an on resistance of the switch.
4. The implantable stimulator device of claim 2 , wherein the expected range is defined by a single threshold.
5. The implantable stimulator device of claim 2 , wherein the expected range is defined by a lower threshold and an upper threshold.
6. The implantable stimulator device of claim 1 , wherein there are N switches corresponding to N electrodes.
7. The implantable stimulator device of claim 1 , wherein the at least one current source comprises at least one constant current source, and wherein the at least one current comprises at least one constant current.
8. The implantable stimulator device of claim 7 , wherein an amplitude of the at least one constant current is adjustable at the at least one constant current source.
9. The implantable stimulator of claim 7 , wherein the at least one constant current source either sources at least one current to the one or more electrodes, or sinks at least one current from the one or more electrodes.
10. The implantable stimulator device of claim 1 , wherein the at least one current source comprises at least one constant voltage source for producing at least one constant voltage to produce the at least one current.
11. The implantable stimulator device of claim 10 , wherein an amplitude of the at least one constant voltage is adjustable at the at least one constant voltage source.
12. The implantable stimulator device of claim 1 , wherein the monitoring circuitry is configured to only measure the at least one voltage only across the switches that are selected to distribute the at least one current to or from the one or more of the electrodes.
13. The implantable stimulator device of claim 1 , wherein the monitoring circuitry is configured to measure the at least one voltage only across switches that not are selected to distribute the at least one current to or from the one or more of the electrodes.
14. The implantable stimulator device of claim 1 , wherein the monitoring circuitry is configured to measure the at least one voltage only across all of the switches.
15. The implantable stimulator device of claim 1 , wherein the at least one current comprises a therapeutic current for stimulating a patient's tissue, and wherein the monitoring circuitry is configured to measure the at least one voltage during the provision of the therapeutic current to the patient's tissue.
16. The implantable stimulator device of claim 1 , wherein the at least one current comprises a test current not intended as therapy for a patient, and wherein the monitoring circuitry is configured to measure the at least one voltage during the provision of the test current.
17. The implantable stimulator device of claim 1 , wherein the monitoring circuitry comprises at least one voltage amplifier for measuring the at least one.
18. The implantable stimulator device of claim 1 , wherein the failure condition comprises an open circuit or a short circuit of one of the electrodes.
19. The implantable stimulator device of claim 1 , wherein the monitoring circuitry further comprises control circuitry, wherein the failure condition is reported to the control circuitry to enable an action.
20. The implantable stimulator device of claim 19 , wherein the action comprises one or more of stopping the current, issuing an alarm, logging the failure condition in a memory in the implantable stimulator device, or telemetry of the failure condition to a device external to the implantable stimulator device.
21. The implantable stimulator device of claim 1 , wherein first and second of the switches are selected to distribute the at least one current to two electrodes, and wherein the monitoring circuitry is configured to measure a first voltage only across the first switch and a second voltage only across the second switch to determine whether a failure condition has occurred.
22. The implantable stimulator device of claim 21 , wherein the first and second voltages are measured simultaneously.
23. The implantable stimulator device of claim 21 , wherein the first and second voltages are not measured simultaneously.
24. The implantable stimulator device of claim 1 , wherein there is only one current source configured to produce one current.
25. An implantable stimulator device, comprising:
a plurality of electrodes;
at least one current source configured to produce at least one current;
a plurality of switches, wherein the switches are selectable to distribute the at least one current to or from one or more of the electrodes; and
monitoring circuitry configured to measure a voltage across each selected switch individually and for determining whether a failure condition has occurred.
26. The implantable stimulator device of claim 25 , wherein the monitoring circuitry determines whether a failure condition has occurred by comparing the voltage across each selected switch to an expected range.
27. The implantable stimulator device of claim 26 , wherein the expected range is based on an on resistance of the switch.
28. The implantable stimulator device of claim 26 , wherein the expected range is defined by a single threshold.
29. The implantable stimulator device of claim 26 , wherein the expected range is defined by a lower threshold and an upper threshold.
30. The implantable stimulator device of claim 25 , wherein the at least one current source comprises at least one constant current source, and wherein the at least one current comprises at least one constant current.
31. The implantable stimulator device of claim 30 , wherein an amplitude of the at least one constant current is adjustable at the at least one constant current source.
32. The implantable stimulator of claim 30 , wherein the at least one constant current source either sources at least one current to the one or more electrodes, or sinks at least one current from the one or more electrodes.
33. The implantable stimulator device of claim 25 , wherein the at least one current source comprises at least one constant voltage source for producing at least one constant voltage to produce the at least one current.
34. The implantable stimulator device of claim 33 , wherein an amplitude of the at least one constant voltage is adjustable at the at least one constant voltage source.
35. The implantable stimulator device of claim 25 , wherein the monitoring circuitry is further configured to measure a voltage across switches that not are selected to distribute the at least one current to or from the one or more of the electrodes.
36. The implantable stimulator device of claim 25 , wherein the at least one current comprises a therapeutic current for stimulating a patient's tissue, and wherein the monitoring circuitry is configured to measure the voltage across each selected switch during the provision of the therapeutic current to the patient's tissue.
37. The implantable stimulator device of claim 25 , wherein the at least one current comprises a test current not intended as therapy for a patient, and wherein the monitoring circuitry is configured to measure the voltage across each selected switch during the provision of the test current.
38. The implantable stimulator device of claim 25 , wherein the monitoring circuitry comprises at least one amplifier for measuring the voltage across each selected switch.
39. The implantable stimulator device of claim 25 , wherein the failure condition comprises an open circuit or a short circuit of one of the electrodes.
40. The implantable stimulator device of claim 25 , wherein the monitoring circuitry further comprises control circuitry, wherein the failure condition is reported to the control circuitry to enable an action.
41. The implantable stimulator device of claim 25 , wherein the voltages across each selected switch are measured simultaneously.
42. The implantable stimulator device of claim 25 , wherein the voltages across each selected switch are not measured simultaneously.