Low Power Loss Current Digital-to-Analog Converter Used in an Implantable Pulse Generator

• US 20140277270A1
• Filed: 05/30/2014
• Published: 09/18/2014
• Est. Priority Date: 05/28/2004
• Status: Active Grant

• Current Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Original Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Inventors: Parramon, Jordi, He, Yuping, Nimmagadda, Kiran
• Granted Patent: US 9,320,899 B2
• Time in Patent Office: Days
• US Class Current: 607/46
• CPC Class Codes: A61N 1/025 Digital circuitry features of electrotherapy devices, e.g. memory, clocks, processors
• CPC Class Codes: A61N 1/36071 Pain
• CPC Class Codes: A61N 1/36125 Details of circuitry or electric components
• CPC Class Codes: A61N 1/378 Electrical supply

Abstract

An implantable stimulation device that includes output current sources and/or sinks configured to provide an output current for a load (i.e., tissue). The output path of the output current source or sink comprises a transistor which operates in a linear mode instead of a saturation mode. Because operation in a linear mode results in smaller drain-to-source voltage drops, power consumption in the output current source or sink (and hence in the implantable stimulator) is reduced, reducing battery or other power source requirements. Operation in the linear mode is facilitated by a load in an input path and a load in the output path (which bears the output current). The loads can be active transistors or passive resistors. A feedback circuit (e.g., an operational amplifier) receives voltages that build up across these loads, and sends a control signal to the gate of the transistor to ensure its linear operation.

Claims

1. An implantable stimulator device, comprising:

a first electrode implantable adjacent to tissue to be stimulated;

a first transistor configured to source a stimulation current along a first output path to the first electrode;

a second electrode implantable adjacent to tissue to be stimulated; and

a second transistor configured to sink the stimulation current along a second output path from the second electrode,

wherein the first and second transistors are controlled to operate in a linear mode.

2. The device of claim 1, wherein the first and second transistors are controlled using feedback from the first and second output paths respectively.

3. The device of claim 1, further comprising a first feedback circuit for controlling the first transistor by receiving a first voltage from the first output path, and a second feedback circuit for controlling the second transistor by receiving a second voltage from the second output path.

4. The device of claim 3, wherein the first and second feedback circuits respectively also receive first and second reference voltages, and wherein the first and second feedback circuits respectively control the first and second transistors by comparing the first and second voltages to the first and second reference voltages.

5. The device of claim 4, wherein the first and second reference voltages are respectively generated using first and second constant current sources.

6. The device of claim 3, wherein the first and second feedback circuits respectively comprise first and second amplifiers.

7. The device of claim 1, further comprising a first resistance in the first output path between the first transistor and a first power supply voltage, and a second resistance in the second output path between the second transistor and a second power supply.

8. The device of claim 7, further comprising a first feedback circuit for controlling the first transistor by receiving a first voltage between the first resistance and the first transistor, and a second feedback circuit for controlling the second transistor by receiving a second voltage between the second resistance and the second transistor.

9. The device of claim 8, wherein the first and second feedback circuits respectively also receive first and second reference voltages, and wherein the first and second feedback circuits respectively control the first and second transistors by comparing the first and second voltages to the first and second reference voltages.

10. The device of claim 9, wherein the first and second feedback circuits respectively comprise first and second amplifiers.

11. The device of claim 9, wherein the first and second reference voltages are respectively generated by passing first and second currents through third and fourth resistances.

12. The device of claim 11, wherein the stimulation current is N times higher than the first and second currents.

13. The device of claim 12, wherein N is proportional to the ratio of the first and third resistances, and the ratio of the second and fourth resistances.

14. An implantable stimulator device, comprising:

a first electrode implantable adjacent to tissue to be stimulated;

a first load configured to source a current along a first output path to the first electrode;

a first feedback circuit configured to receive a first voltage on the first output path, and to control the first load to source the current along the first output path;

a second electrode implantable adjacent to tissue to be stimulated;

a second load configured to sink the current along a second output path from the second electrode; and

a second feedback circuit configured to receive a second voltage on the second output path, and to control the second load to sink the current along the second output path.

15. The device of claim 14, wherein the first and second loads comprise transistors.

16. The device of claim 15, wherein the first and second feedback circuits respective control the first and second transistors to operate in a linear mode.

17. The device of claim 14, wherein the first and second feedback circuits respectively also receive first and second reference voltages, and wherein the first and second feedback circuits respectively control the first and second load by comparing the first and second voltages to the first and second reference voltages.

18. The device of claim 17, wherein the first and second reference voltages are respectively generated using first and second constant current sources.

19. The device of claim 14, wherein the first and second feedback circuits respectively comprise first and second amplifiers.

20. The device of claim 14, further comprising a third load in the first output path between the first load and a first power supply voltage, and a fourth load in the second output path between the second load and a second power supply.

21. The device of claim 20, wherein the first voltage is between the first and third loads, and wherein the second voltage is between the second and fourth loads.

22. The device of claim 21, wherein the first and second feedback circuits respectively also receive first and second reference voltages, and wherein the first and second feedback circuits respectively control the first and second loads by comparing the first and second voltages to the first and second reference voltages.

23. The device of claim 22, wherein the first and second feedback circuits respectively comprise first and second amplifiers.

24. The device of claim 22, wherein the first and second reference voltages are respectively generated by passing first and second currents through fifth and sixth loads.

25. The device of claim 24, wherein the stimulation current is N times higher than the first and second currents.

26. The device of claim 25, wherein N is proportional to the ratio of resistances of the third and fifth loads, and the ratio of resistances of the fourth and sixth loads.