Systems and methods for communicating with an implantable stimulator

1. An implantable medical device, comprising:

a coil; and

telemetry circuitry coupled to the coil for allowing data-containing signals to be received from at least one external device, the telemetry circuitry comprising a first telemetry receiver for receiving data over a first telemetry link in accordance with a first frequency modulation telemetry scheme, and a second telemetry receiver for receiving data over a second telemetry link in accordance with a second On-Off-Keying telemetry scheme, wherein at least the second telemetry receiver is configured to receive calibration data used to synchronize a reference clock signal with a frequency used to transmit or receive data using the first frequency modulated telemetry scheme.

2. The implantable medical device of claim 1 , wherein the first telemetry scheme comprises a frequency shift key telemetry scheme wherein a binary ‘1’ is represented by a transmitted signal of a first frequency, and wherein a binary ‘0’ is represented by a transmitted signal of a second frequency.

3. The implantable medical device of claim 1 , wherein the second telemetry scheme comprises an On-Off-Keying (OOK) Pulse Width Modulation (PWM) telemetry scheme wherein a binary ‘0’ is represented by a first pulse width and a binary ‘1’ is represented by a second pulse width, and wherein a transition between one data bit and an adjacent data bit is marked by a change in a transmitted data signal from an ON to an OFF state or from an OFF to an ON state, wherein the ON state is characterized by the presence of a data signal having a frequency, and wherein the OFF state is characterized by the absence of the data signal.

4. The implantable medical device of claim 1 , wherein the telemetry circuitry is bidirectional for allowing data signals to be sent to and received from the at least one external device.

5. The implantable medical device of claim 1 , wherein the first telemetry link is a radio frequency (RF) telemetry link, and the second telemetry link is an inductive telemetry link.

6. The implantable medical device of claim 5 , wherein the first communication scheme comprises a frequency shift key (FSK) communication scheme, and the second communication scheme comprises an On-Off-Keying (OOK) Pulse Width Modulation (PWM) communication scheme.

7. The implantable medical device of claim 1 , further comprising at least one electrode for stimulating the tissue of a patient.

8. A method for receiving communications in an implantable medical device, comprising:

receiving a first modulated signal, wherein the first modulated signal comprises first data modulated with pulse width modulation;

receiving a second modulated signal, wherein the second modulated signal comprises second data modulated with frequency modulation;

using a first telemetry receiver in the implantable medical device to demodulate the received first modulated signal to recover the first data; and

using a second telemetry receiver in the implantable medical device to demodulate the received second modulated signal to recover the second data, wherein the first data comprises calibration data used to synchronize a reference clock signal with a frequency used to transmit the second modulated signal.

9. The method of claim 8 , wherein the pulse width modulation comprises on-off keying (OOK) modulation.

10. The method of claim 8 , wherein the frequency modulation comprises frequency shift keying (FSK) modulation.

11. The method of claim 8 , wherein the implantable medical device generates the reference clock signal used by the second telemetry receiver.

12. The method of claim 8 , wherein the first data comprises a start bit and a number of control bits.

13. The method of claim 8 , wherein the implantable medical device comprises at least one electrode for stimulating a patient's tissue.

14. The method of claim 8 , wherein the first data enables the second telemetry receiver to receive the second modulated signal.

15. The method of claim 8 , wherein the first and second telemetry receivers are coupled to a coil for receiving the first and second modulated signals.

16. A method for receiving communications in an implantable medical device, comprising:

receiving a second modulated signal at a second telemetry receiver in the implantable medical device, wherein the second modulated signal comprises a second telemetry scheme;

disabling reception of the second modulated signal upon the occurrence of a condition in the implantable medical device;

when reception of the second modulated signal is disabled, using a first telemetry receiver in the implantable medical device to listen for and demodulate a received first modulated signal to recover first data, wherein the first modulated signal comprises a first telemetry scheme; and

using the recovered first data to enable the reception of the previously disabled second modulated signal.

17. The method of claim 16 , wherein the first telemetry scheme comprises on-off keying (OOK) modulation.

18. The method of claim 16 , wherein the second telemetry scheme comprises frequency shift keying (FSK) modulation.

19. The method of claim 16 , wherein the implantable medical device generates a reference clock signal used by the second telemetry receiver.

20. The method of claim 19 , wherein the first data comprises calibration data used to synchronize the reference clock signal with a frequency used to transmit the second modulated signal.

21. The method of claim 16 , wherein the implantable medical device comprises at least one electrode for stimulating a patient's tissue.

22. The method of claim 16 , wherein reception of the second modulated signal is disabled because of a low power condition in the implantable medical device.

23. The method of claim 16 , wherein reception of the second modulated signal is disabled because the implantable medical device enters a hibernation or storage mode state.

24. The method of claim 16 , wherein the first and second telemetry receivers are coupled to a coil for receiving the first and second modulated signals.