Circuit for an implantable device
An integrated circuit includes: a radio-frequency (RF) to direct current (DC) rectifying circuit coupled to one or more antenna on an implantable wirelessly powered device, the rectifying circuit configured to: rectify an input RF signal received at the one or more antennas and from an external controller through electric radiative coupling; and extract DC electric power and configuration data from the input RF signal; a logic control circuit connected to the rectifying circuit and a driving circuit, the logic control circuit configured to: generate a current for the driving circuit solely using the extracted DC electrical power; in accordance with the extracted configuration data, set polarity state information for each electrode; and a driving circuit coupled to one or more electrode, the driving circuit comprising current mirrors and being configured to: steer, to each electrode and via the current mirrors, a stimulating current solely from the generated current.
1. An integrated circuit for an implantable wirelessly powered device for implantation in a patient's body, the circuit comprising:
a radio-frequency (RF) to direct current (DC) rectifying circuit coupled to one or more antenna on the implantable wirelessly powered device, the rectifying circuit configured to:
rectify an input RF signal received non-inductively at the one or more antennas and from an external controller through electric radiative coupling; and
extract DC electric power and configuration data from the input RF signal;
a logic control circuit connected to the rectifying circuit and a driving circuit that is coupled to two or more electrodes, the logic control circuit configured to:
generate a current for the driving circuit solely using the extracted DC electrical power; and
in accordance with the extracted configuration data, set polarity state information for each of the two or more electrodes; and
a driving circuit coupled to the two or more electrodes, the driving circuit comprising current mirrors and configured to:
steer, to each of the two or more electrodes and via the current mirrors, a stimulating current solely from the generated current to modulate neural tissue within the patient's body such that the two or more electrodes conduct stimulating currents of substantially identical amplitude when activated to apply stimulation to neural tissue.
2. The integrated circuit of claim 1 , wherein the driving circuit comprises: a current source digital to analog circuit (DAC) and a current sink digital to analog circuit (DAC), the current source DAC and the current sink DAC are complementary to each other and both are connected to each electrode via the current mirrors wherein the stimulating current at each of the two or more electrodes is determined by a current mirror ratio and wherein the configuration data comprises the current mirror ratio.
3. The integrated circuit of claim 2 , wherein the current mirror ratio matches the number of electrodes.
4. The integrated circuit of claim 1 , wherein the driving circuit comprises: a switch bank configured to control a polarity state for each electrode.
5. The integrated circuit of claim 1 , wherein the driving circuit comprises:
a variable shunt resistor adapted to reduce a ripple on the electrode connected thereto when the stimulating current has just ended.
6. The integrated circuit of claim 1 , further comprising: a discharge delay timer to delay the onset of capacitors coupled to each of the electrodes.
7. The integrated circuit of claim 1 , further comprising: a power on reset (PoR) circuit to maintain default state information for each electrode and default parameters for the stimulating current for each electrode, the PoR circuit configured to be trigged on by a rising edge of the input RF signal and turned off by a falling edge of the input RF signal.
8. The integrated circuit of claim 1 , further comprising: one or more address control bits, configurable as a logic address of the implantable device wirelessly powered by the extracted electric power.
9. The integrated circuit of claim 1 , wherein the rectifying circuit comprises a diode bridge.
10. The integrated circuit of claim 1 , wherein the rectifying circuit is coupled to a differential antenna on the implantable wirelessly powered device, wherein said two or more antenna comprises a differential antenna.
11. The integrated circuit of claim 1 , wherein the rectifying circuit comprises: an amplitude modulation (AM) detection circuit to extract electric power and configuration data from the input RF signal received non-inductively at the one or more antennas.
12. The integrated circuit of claim 1 , wherein the logic control circuit comprises: a state machine to record state information for each electrode based on the extracted configuration data, the configuration data including polarity setting for each electrode.
13. The integrated circuit of claim 1 , wherein the logic control circuit is further configured to set polarity state for each electrode during a communication initialization pulse.
14. The integrated circuit of claim 1 , wherein the logic control circuit comprises a timer circuit to control a duration the generated current for the driving circuit.