Pulse-density modulation to synthesize stimulation waveforms on an implantable device
A wirelessly powered implantable stimulator device includes one or more antenna configured to receive an input signal non-inductively from an external antenna, the input signal containing (i) electrical energy to operate the implantable stimulator device and (ii) configuration data according to which a pulse-density modulation (PDM) encoded stimulus waveform signal is retrieved to synthesize a desired stimulation waveform; a circuit coupled to the one or more antenna; and one or more electrodes coupled to the circuit and configured to apply the desired stimulation waveform to neural tissue, wherein the circuit is configured to: rectify the input signal received at the one or more antennas non-inductively; extract the electrical energy and the configuration data from the input signal; and in accordance with the extracted configuration data, retrieve the pulse-density modulation (PDM) signal to synthesize the desired stimulation waveform therefrom.
1. A method to synthesize a stimulus waveform, the method comprising:
receiving, by one or more antennas of an implantable stimulation device and from an external module, an input signal through non-inductive coupling;
rectifying the input signal, the input signal containing
(i) electrical energy to operate the implantable stimulation device, and
(ii) configuration data including parameters for generating a specific stimulus waveform;
extracting the electrical energy and the configuration data from the rectified input signal; and
based on the parameters in the configuration data,
(i) selecting a digital representation of a pulse density modulation (PDM) encoded stimulus waveform signal from a memory device of a circuit of the implantable stimulation device, wherein the circuit is coupled to the one or more antennas and includes (i) the memory device that stores the digital representation of the PDM encoded stimulus waveform for generating the specific stimulus waveform, (ii) a clock, (iii) an oscillator device, and (iv) one or more electrode drivers that comprise at least an H bridge electrode driver,
(ii) controlling the oscillator device of the implantable stimulation device to signal the clock to clock the PDM encoded stimulus waveform signal and convert the digital representation of the PDM encoded stimulus waveform signal using the extracted electrical energy into the specific stimulus waveform, and
(iii) generating the specific stimulus waveform with the one or more electrode drivers of the implantable stimulation device.
2. The method of claim 1 , further comprising:
applying the specific stimulus waveform at one or more electrodes of the implantable stimulation device, wherein the one or more electrodes are coupled to the circuit.
3. The method of claim 1 , further comprising:
tuning the PDM encoded stimulus waveform signal to treat a particular condition for a subject.
4. The method of claim 1 , further comprising:
pre-loading the PDM encoded stimulus waveform signal as a bit stream such that the specific stimulus waveform is generated at least in part by using the oscillator device and the clock to serially shift out the bit stream.
5. An implantable stimulation device receiving instructions from an external module and configured to perform operations comprising:
receiving, by one or more antennas of the implantable stimulation device and from the external module, an input signal through non-inductive coupling;
rectifying the input signal, the input signal containing
(i) electrical energy to operate the implantable stimulation device, and
(ii) configuration data including parameters for generating a specific stimulus waveform;
extracting the electrical energy and the configuration data from the rectified input signal; and
based on the parameters in the configuration data,
(i) selecting a digital representation of a pulse density modulation (PDM) encoded stimulus waveform signal from a memory device of a circuit of the implantable stimulation device, wherein the circuit is coupled to the one or more antennas and includes (i) the memory device that stores the digital representation of the PDM encoded stimulus waveform for generating the specific stimulus waveform, (ii) a clock, (iii) an oscillator device, and (iv) one or more electrode drivers that comprise at least an H bridge electrode driver,
(ii) controlling the oscillator device of the implantable stimulation device to signal the clock to clock the PDM encoded stimulus waveform signal and convert the digital representation of the PDM encoded stimulus waveform signal using the extracted electrical energy into the specific stimulus waveform, and
(iii) generating the specific stimulus waveform with the one or more electrode drivers of the implantable stimulation device.
6. The implantable stimulation device of claim 5 , wherein the operations further comprise:
applying the specific stimulus waveform at one or more electrodes of the implantable stimulation device, wherein the one or more electrodes are coupled to the circuit.
7. The implantable stimulation device of claim 5 , further comprising:
tuning the PDM encoded stimulus waveform signal to treat a particular condition for a subject.
8. The implantable stimulation device of claim 5 , further comprising:
pre-loading the PDM encoded stimulus waveform signal as a bit stream such that the specific stimulus waveform is generated at least in part by using the oscillator device and the clock to serially shift out the bit stream.
9. The implantable stimulation device of claim 5 , wherein the memory of the circuit stores digital representations of more than one PDM encoded stimulus waveform signals.