Abstract: An improved transceiver circuit particularly useful in an inductively coupled wireless communication system such as an implantable medical device system is disclosed. The improved transceiver circuit is switchable to assume a serial L-C configuration in the transmit mode and a parallel L-C configuration in the receive mode, but does not require high voltage switches. A low-drive transmitter and a high-input-impedance receiver are used, which reduces power consumption in receive mode, while still maintaining good transmitter performance.

Abstract: Disclosed are methods for synchronizing the time basis of logged data between an implantable medical device such as an IPG and an external device. The IPG logs various operational parameters as data and associates the same with a possibly-inaccurate IPG time stamp and a sequence number. Periodically, the external device sends accurate true time data to the IPG, which, like the operational parameter data, is logged with an IPG time stamp and a next sequence number. The IPG then orders the data sequences and timing sequences by time stamp in a combined data log, and divides that data log into regions in accordance with reset conditions apparent in the time stamp data. Slopes indicative of the relation between true time and time stamps are calculated for various regions on an intra-region or inter-region basis, which then allows for true time estimates to be calculated for the data sequences, thus providing an accurate time basis for the logged data.

Abstract: Improved power circuitry for charging a battery in an implantable medical device is disclosed. The improved power circuitry uses a DC-DC converter positioned between the rectifier and the battery in the implant to be charged, and operates to boost the voltage produced by the rectifier to a higher compliance voltage used to charge the battery. Because the rectifier can now produce a smaller DC voltage, the AC voltage preceding the rectifier (the coil voltage), can also be lessened. Lowering the coil voltage reduces the amount of heat generated by the coil, which reduces the overall heat generated by the implant during receipt of a magnetic charging field from an external charger during a charging session, which improves patient safety. Additionally, a reduced coil voltage means that the external charger can reduce the intensity of the magnetic charging field, which also reduces heat generated in the external charger during the charging session.

Abstract: An implantable microstimulator configured for implantation beneath a patient's skin for tissue stimulation to prevent and/or treat various disorders, uses a self-contained power source. Periodic or occasional replenishment of the power source is accomplished, for example, by inductive coupling with an external device. A bidirectional telemetry link allows the microstimulator to provide information regarding the system's status, including the power source's charge level, and stimulation parameter states. Processing circuitry automatically controls the applied stimulation pulses to match a set of programmed stimulation parameters established for a particular patient. The microstimulator preferably has a cylindrical hermetically sealed case having a length no greater than about 27 mm and a diameter no greater than about 3.3 mm. A reference electrode is located on one end of the case and an active electrode is located on the other end.

Abstract: An improved implantable pulse generator (IPG) containing graceful shutdown circuitry is disclosed. A magnet sensor senses the presence of an emergency shutdown magnet. Output of the magnet sensor is conditioned by a signal conditioning circuit. Output of the signal conditioning circuit is delayed by a delay element before being fed to a power cut-off switch, which cuts-off power to the IPG circuitry. An interrupt signal is routed from before the delay element to the IPG processor as an indicator of imminent shutdown. The processor launches shutdown routine that carries out shutdown operations such as logging the emergency shutdown event, saving and closing open files, saving data from volatile memory to non-volatile memory, etc., before the power cut-off switch is activated upon elapsing of delay provided by the delay element. The magnet sensor, signal conditioning circuit, and delay element are powered separately from the rest of the circuitry of the IPG.

Abstract: An implantable microstimulator configured to be implanted beneath a patient's skin for tissue stimulation employs a bi-directional RF telemetry link for allowing data-containing signals to be sent to and from the implantable microstimulator from at least two external devices. Further, a separate electromagnetic inductive telemetry link allows data containing signals to be sent to the implantable microstimulator from at least one of the two external devices. The RF bidirectional telemetry link allows the microstimulator to inform the patient or clinician regarding the status of the microstimulator device, including the charge level of a power source, and stimulation parameter states. The microstimulator has a cylindrical hermetically sealed case having a length no greater than about 27 mm and a diameter no greater than about 3.3 mm. A reference electrode is located on one end of the case and an active electrode is located on the other end of the case.

Abstract: An improved external charger for a battery in an implantable medical device (implant), and technique for charging batteries in multiple implants using such improved external charger, is disclosed. During charging, values for a parameter measured in the implants are reported from the implants to the external charger. The external charger infers from the magnitudes of the parameters which of the implants has the highest and lowest coupling to the external charger, and so designates those implants as “hot” and “cold.” The intensity of the magnetic charging field is optimized for the cold implant consistent with the simulation to ensure that that the cold implant is charged with a maximum (fastest) battery charging current. The duty cycle of the magnetic charging field is also optimized for the hot implant consistent with the simulation to ensure that the hot implant does not exceed the power dissipation limit.

Abstract: Disclosed herein are circuits and methods for a multi-electrode implantable stimulator device incorporating one decoupling capacitor in the current path established via at least one cathode electrode and at least one anode electrode. In one embodiment, the decoupling capacitor may be hard-wired to a dedicated anode on the device. The cathodes are selectively activatable via stimulation switches. In another embodiment, any of the electrodes on the devices can be selectively activatable as an anode or cathode. In this embodiment, the decoupling capacitor is placed into the current path via selectable anode and cathode stimulation switches. Regardless of the implementation, the techniques allow for the benefits of capacitive decoupling without the need to associate decoupling capacitors with every electrode on the multi-electrode device, which saves space in the body of the device.

Abstract: An improved implantable pulse generator (IPG) containing improved telemetry circuitry is disclosed. The IPG includes charging and telemetry coils within the IPG case, which increases their mutual inductance and potential to interfere with each other; particularly problematic is interference to the telemetry coil caused by the charging coil. To combat this, improved telemetry circuitry includes decoupling circuitry for decoupling the charging coil during periods of telemetry between the IPG and an external controller. Such decoupling circuitry can comprise use of pre-existing LSK circuitry during telemetry, or new discrete circuitry dedicated to decoupling. The decoupling circuitry is designed to prevent or at least reduce induced current flowing through the charging coil during data telemetry.

Abstract: An improved external charger for a battery in an implantable medical device (implant), and technique for charging the battery using such improved external charger, is disclosed. In one example, simulation data is used to model the power dissipation of the charging circuitry in the implant at varying levels of implant power. A power dissipation limit is chosen to constrain the charging circuitry from producing an inordinate amount of heat to the tissue surrounding the implant, and duty cycles are determined for the various levels of input intensities to ensure that the power limit is not exceeded. A maximum simulated average battery current determines the optimal (i.e., quickest) battery charging current, and at least an optimal value for a parameter indicative of that current, for example, the voltage across the battery charging circuitry, is determined and stored in the external charger.

Abstract: A combination, voltage converter circuit for use within an implantable device, such as a microstimulator, uses a coil, instead of capacitors, to provide a voltage step up and step down conversion functions. The output voltage is controlled, or adjusted, through duty-cycle modulation. In accordance with one aspect of the invention, applicable to implantable devices having an existing RF coil through which primary or charging power is provided, the existing RF coil is used in a time-multiplexing scheme to provide both the receipt of the RF signal and the voltage conversion function. This minimizes the number of components needed within the device, and thus allows the device to be packaged in a smaller housing or frees up additional space within an existing housing for other circuit components. In accordance with another aspect of the invention, the voltage up/down converter circuit is controlled by a pulse width modulation (PWM) low power control circuit.

Abstract: An implantable microstimulator configured to be implanted beneath a patient's skin for tissue stimulation employs a bi-directional RF telemetry link for allowing data-containing signals to be sent to and from the implantable microstimulator from at least two external devices. Further, a separate electromagnetic inductive telemetry link allows data containing signals to be sent to the implantable microstimulator from at least one of the two external devices. The RF bidirectional telemetry link allows the microstimulator to inform the patient or clinician regarding the status of the microstimulator device, including the charge level of a power source, and stimulation parameter states. The microstimulator has a cylindrical hermetically sealed case having a length no greater than about 27 mm and a diameter no greater than about 3.3 mm. A reference electrode is located on one end of the case and an active electrode is located on the other end of the case.

Abstract: A method for configuring stimulation pulses in an implantable stimulator device having a plurality of electrodes is disclosed, which method is particularly useful in adjusting the electrodes by current steering during initialization of the device. In one aspect, a set of ideal pulses for patient therapy is determined, in which at least two of the ideal pulses are of the same polarity and are intended to be simultaneous applied to corresponding electrodes on the implantable stimulator device during an initial duration. These pulses are reconstructed into fractionalized pulses, each comprised of pulse portions. The fractionalized pulses are applied to the corresponding electrodes on the device during a final duration, but the pulse portions of the fractionalized pulses are not simultaneously applied during the final duration.

Abstract: Disclosed herein are circuits and methods for a multi-electrode implantable stimulator device incorporating one decoupling capacitor in the current path established via at least one cathode electrode and at least one anode electrode. In one embodiment, the decoupling capacitor may be hard-wired to a dedicated anode on the device. The cathodes are selectively activatable via stimulation switches. In another embodiment, any of the electrodes on the devices can be selectively activatable as an anode or cathode. In this embodiment, the decoupling capacitor is placed into the current path via selectable anode and cathode stimulation switches. Regardless of the implementation, the techniques allow for the benefits of capacitive decoupling without the need to associate decoupling capacitors with every electrode on the multi-electrode device, which saves space in the body of the device.

Abstract: An improved architecture for an implantable medical device such as an implantable pulse generator (IPG) is disclosed. In one embodiment, the various functional blocks for the IPG are incorporated into a signal integrated circuit (IC). Each of the functional blocks communicate with each other, and with other off-chip devices if necessary, via a centralized bus governed by a communication protocol. To communicate with the bus and to adhere to the protocol, each circuit block includes bus interface circuitry adherent with that protocol. Because each block complies with the protocol, any given block can easily be modified or upgraded without affecting the design of the other blocks, facilitating debugging and upgrading of the IPG circuitry. Moreover, because the centralized bus can be taken off the integrated circuit, extra circuitry can easily be added off chip to modify or add functionality to the IPG without the need for a major redesign of the main IPG IC.

Abstract: Disclosed herein are circuits and methods for generating a compliance voltage from a battery voltage in an implantable stimulator device. In one embodiment, the battery voltage is boosted to form the compliance voltage for driving the current sources (DACs) that provide therapeutic current to the electrodes on the device. Such improved boosting circuitry is preferably cascaded and comprises two stages. The first stage is preferably a step-up converter, which is used to generate an intermediate voltage from the battery voltage. The second stage is preferably a charge pump, which is used to generate the compliance voltage from the intermediate voltage. By splitting the boosting into stages, power efficiency during generation of high voltages is improved compared to the use of step-up converters and resolution in setting the compliance voltage is improved compared to the use of charge pumps alone.

Abstract: A method and system of providing therapy to a patient implanted with an array of electrodes is provided. A train of electrical stimulation pulses is conveyed within a stimulation timing channel between a group of the electrodes to stimulate neural tissue, thereby providing continuous therapy to the patient. Electrical parameter is sensed within a sensing timing channel using at least one of the electrodes, wherein the first stimulation timing channel and sensing timing channel are coordinated, such that the electrical parameter is sensed during the conveyance of the pulse train within time slots that do not temporally overlap any active phase of the stimulation pulses.

Abstract: Disclosed herein is a current generation architecture for an implantable stimulator device such as an Implantable Pulse Generator (IPG). Current source and sink circuitry are both divided into coarse and fine portions, which respectively can provide a coarse and fine current resolution to a specified electrode on the IPG. The coarse portion is distributed across all of the electrodes and so can source or sink current to any of the electrodes. The coarse portion is divided into a plurality of stages, each of which is capable via an associated switch bank of sourcing or sinking a coarse amount of current to or from any one of the electrodes on the device. The fine portion of the current generation circuit preferably includes source and sink circuitry dedicated to each of the electrode on the device, which can comprise digital-to-analog current converters (DACs).

Abstract: Systems of techniques for controlling charge flow during the electrical stimulation of tissue. In one aspect, a method includes receiving a charge setting describing an amount of charge that is to flow during a stimulation pulse that electrically stimulates a tissue, and generating and delivering the stimulation pulse in a manner such that an amount of charge delivered to the tissue during the stimulation pulse accords with the charge setting.

Abstract: An exemplary system for communicating with an implantable stimulator includes a coil configured to transmit a signal modulated with on-off keying (OOK) modulation to transmit control data. The system further includes a first telemetry receiver in the implantable stimulator configured to receive the control data in accordance with the OOK modulation. An exemplary method of communicating with an implantable stimulator includes modulating a signal with control data using OOK modulation and transmitting the signal to the implantable stimulator.