Abstract: The problem of a potentially high amount of supra-threshold charge passing through the patient's tissue at the end of an Implantable Pulse Generator (IPG) program is addressed by circuitry that periodically dissipates only small amount of the charge stored on capacitances (e.g., DC-blocking capacitors) during a pulsed post-program recovery period. This occurs by periodically activating control signals to turn on passive recovery switches to form a series of discharge pulses each dissipating a sub-threshold amount of charge. Such periodic pulsed dissipation may extend the duration of post-program recovery, but is not likely to be noticeable by the patient when the programming in the IPG changes from a first to a second program. Periodic pulsed dissipation of charge may also be used during a program, such as between stimulation pulses.

Abstract: Stimulator circuitry useable in a stimulator device is disclosed. The circuitry includes biasing circuitry that can be used to generate a voltage to allow any one or more electrode on the device (including the case electrode and lead-based electrodes) to provide a common mode voltage (Vcm) to the tissue. Providing a stable Vcm to the tissue is particularly useful when sensing neural responses to the stimulation that the device provides. Switches are provided to couple each of the electrode nodes to one or more buses. This allows any of the electrodes to be selected to provide bipolar or monopolar stimulation, or to act to provide Vcm to the tissue during relevant pulses phases, including during passive charge recovery.

Abstract: Sense amplifier circuits particularly useful in sensing neural responses in an Implantable Pulse Generator (IPG) are disclosed. The IPG includes a plurality of electrodes, with one selected as a sensing electrode and another selected as a reference to differentially sense the neural response in a manner that subtracts a common mode voltage (e.g., stimulation artifact) from the measurement. The circuits include a differential amplifier which receives the selected electrodes at its inputs, and comparator circuitries to assess each differential amplifier input to determine whether it is of a magnitude that is consistent with the differential amplifier's input requirements. Based on these determinations, an enable signal is generated which informs whether the output of the differential amplifier validly provides the neural response at any point in time.

Abstract: A system can utilize interleaving periods or waveforms to stimulate patient tissue and sense signals using the stimulation electrodes. For example, the system can utilize alternating therapeutic periods and sensing periods. As another example, the system can alternate between biphasic waveforms having opposite temporal orders of positive and negative phases. As another example, waveforms that differ in a parameter, such as amplitude or pulse width, can be interleaved to provide different information in the respective sensed signals.

Abstract: Regulator circuitry for producing a regulated output voltage in an implantable stimulation device and associated methods are disclosed. The regulator circuitry is particularly useful where a load current drawn from the output voltage involves transients, such as occurs when the output voltage is used to power a charge pump that creates a higher power supply voltage (e.g., a compliance voltage) in the device. The output current is sampled and downscaled in the regulator, and is further mirrored and filtered. This filtered current provides a control voltage in which transients are minimized and smoothed, and which is more suitable for use as a feedback voltage when producing the output voltage.

Abstract: Methods and circuitry for calibrating stimulation circuitry in an implantable stimulator device (ISD) is disclosed. The ISD can sense neural response to the stimulation, and use an algorithm to assess those responses and determine a therapeutic window for a particular stimulation parameter, such as amplitude. Stimulation circuitry in the ISD is programmed with information indicative of the determined therapeutic window, such as by programming a minimum and/or maximum current amplitude. As well as restricting operation of the stimulation circuitry to within the therapeutic amplitude window, such programming calibrates the stimulation circuitry and allows an expanded range of, or all of, amplitude values supported by the stimulation circuitry to be used, which allows the amplitude to be incremented in smaller current increments.

Abstract: Passive tissue biasing circuitry in an Implantable Pulse Generator (IPG) is disclosed to facilitate the sensing of neural responses by holding the voltage of the tissue to a common mode voltage (Vcm). The IPG's conductive case electrode, or any other electrode, is passively biased to Vcm using a capacitor, as opposed to actively driving such electrode to a prescribed voltage using a voltage source. Once Vcm is established, voltages accompanying the production of stimulation pulses will be referenced to Vcm, which eases neural response sensing. An amplifier can be used to set a virtual reference voltage and to limit the amount of current that flows to the case during the production of Vcm. Circuitry can be used to monitor the virtual reference voltage to enable sensing neural responses, and to set a compliance voltage for the current generation circuitry.

Abstract: The disclosed techniques allow for externalizing errors from an implantable medical device using the device's charging coil, for receipt at an external charger or other external device. Transmission of errors in this manner is particularly useful when telemetry of error codes through a traditional telemetry coil in the implant is not possible, for example, because the error experienced is so fundamental as to preclude use of such traditional means. By externalizing the error via the charging coil, and though the use of robust error modulation circuitry in the implant designed to be generally insensitive to fundamental errors, the external charger can be consulted to understand the failure mode involved, and to take appropriate action.

Abstract: An implantable pulse generator (IPG) is disclosed having a plurality of electrode nodes, each electrode node configured to be coupled to an electrode to provide stimulation pulses to a patient's tissue. The IPG includes a digital-to-analog converter configured to amplify a reference current to a first current specified by first control signals; a first resistance configured to receive the first current, wherein a voltage across the first resistance is held to a reference voltage at a first node; a plurality of branches each comprising a second resistance and configured to produce a branch current, wherein a voltage across each second resistance is held to the reference voltage at second nodes; and a switch matrix configurable to selectively couple any branch current to any of the electrode nodes via the second nodes.

Abstract: The problem of a potentially high amount of supra-threshold charge passing through the patient's tissue at the end of an Implantable Pulse Generator (IPG) program is addressed by circuitry that periodically dissipates only small amount of the charge stored on capacitances (e.g., DC-blocking capacitors) during a pulsed post-program recovery period. This occurs by periodically activating control signals to turn on passive recovery switches to form a series of discharge pulses each dissipating a sub-threshold amount of charge. Such periodic pulsed dissipation may extend the duration of post-program recovery, but is not likely to be noticeable by the patient when the programming in the IPG changes from a first to a second program. Periodic pulsed dissipation of charge may also be used during a program, such as between stimulation pulses.

Abstract: Digital-to-Analog (DAC) circuitry for an implantable pulse generator is disclosed which is used to program currents at the electrodes. Calibration circuitry allows the positive and negative currents produced at each electrode to be independently calibrated to achieve an ideal (linear) response across a range of amplitude values provided to the DAC circuitry by a digital amplitude bus. The calibration circuitry includes electrode gain and electrode offset circuitry for each of the electrodes. Current range DAC circuitry is also provided which can be used to adjust the gain and offset current at all of the electrodes. The current range DAC circuitry is particularly useful when spanning a range of therapeutic currents for a patient, and allows all possible amplitude values provided by the digital bus to be used to span the range. This can improve (reduce) the current resolution of the electrode currents with each amplitude value step.

Abstract: Recovery circuitry for passively recovering charge from capacitances at electrodes in an Implantable Pulse Generator (IPG) is disclosed. The passive recovery circuitry includes passive recovery switches intervening between each electrode node and a common reference voltage, and each switch is in series with a variable resistance that may be selected based on differing use models of the IPG. The passive recovery switches may also be controlled in different modes. For example, in a first mode, the only recovery switches closed after a stimulation pulse are those associated with electrodes used to provide stimulation. In a second mode, all recovery switches are closed after a stimulation pulse, regardless of the electrodes used to provide stimulation. In a third mode, all recovery switches are closed continuously, which can provide protection when the IPG is in certain environments (e.g., MRI), and which can also be used during stimulation therapy itself.

Abstract: A compliance voltage management algorithm is disclosed for managing the compliance voltage, VH, that powers the DAC circuitry in a stimulator device. A user can use a user interface associated with an external programming device to define a time-varying stimulation waveform to be programmed into the stimulator device. The algorithm analyzes the prescribed waveform and determines a number of groups of pulses that will be treated similarly from a VH management standpoint. Optimal compliance voltages are determined for each group, as are the rise and fall rates at which VH is able to change at transitions between groups. These rise or fall rates in VH are then used to set when the compliance voltage should increase or decrease. For example, the algorithm will automatically set VH to start rising in advance of a transition so that it is at the proper higher value when the transition occurs.

Abstract: A field measurement algorithm and measuring circuitry in an implantable stimulator, and an field modelling algorithm operable in an external device, are used to determine an electric field in a patient's tissue. The field measuring algorithm provides at least one test current between two electrodes, and a plurality of voltage differentials are measured at different combinations of the electrodes. The voltage differential data is telemetered to the field modelling algorithm which determines directional resistance at different locations in the patient's tissue. The field modelling algorithm can then use a stimulation program selected for the patient and the determined directional resistances to determine voltages in the patient's tissue at various locations, which in turn can be used to model a more-accurate electric field in the tissue, and preferably to render an electric field image for display in a graphical user interface of the external device.

Abstract: An architecture is disclosed for an Implantable Pulse Generator having improved compliance voltage monitoring and adjustment software and hardware. Software specifies which stimulation pulses are to be measured as relevant to monitoring and adjusting the compliance voltage. Preferably, specifying such pulses occurs by setting a compliance monitoring instruction (e.g., a bit) in the program that defines the pulse, and the compliance monitor bit instruction may be set at a memory location defining a particular pulse phase during which the compliance voltage should be monitored. When a compliance monitor instruction issues, the active electrode node voltages are monitored and compared to desired ranges to determine whether they are high or low. Compliance logic operates on these high/low signals and processes them to decide whether to issue a compliance voltage interrupt to the microcontroller, which can then command the compliance voltage generator to increase or decrease the compliance voltage.

Abstract: Recovery circuitry for passively recovering charge from capacitances at electrodes in an Implantable Pulse Generator (IPG) is disclosed. The passive recovery circuitry includes passive recovery switches intervening between each electrode node and a common reference voltage, and each switch is in series with a variable resistance that may be selected based on differing use models of the IPG. The passive recovery switches may also be controlled in different modes. For example, in a first mode, the only recovery switches closed after a stimulation pulse are those associated with electrodes used to provide stimulation. In a second mode, all recovery switches are closed after a stimulation pulse, regardless of the electrodes used to provide stimulation. In a third mode, all recovery switches are closed continuously, which can provide protection when the IPG is in certain environments (e.g., MRI), and which can also be used during stimulation therapy itself.

Abstract: An architecture is disclosed for an Implantable Pulse Generator having improved compliance voltage monitoring and adjustment software and hardware. Software specifies which stimulation pulses are to be measured as relevant to monitoring and adjusting the compliance voltage. During compliance voltage monitoring, “high-side” anode electrode node voltages referenced to the compliance voltage are considered as are “low-side” cathode electrode node voltages referenced to ground. Translation stages are used to convert only the anode electrode node voltages to ground as low-side signals. This allows compliance voltage monitoring and adjustment to occur using only low-side signals, which eases sensing and reduces design complexity.

Abstract: A field measurement algorithm and measuring circuitry in an implantable stimulator, and an field modelling algorithm operable in an external device, are used to determine an electric field in a patient's tissue. The field measuring algorithm provides at least one test current between two electrodes, and a plurality of voltage differentials are measured at different combinations of the electrodes. The voltage differential data is telemetered to the field modelling algorithm which determines directional resistance at different locations in the patient's tissue. The field modelling algorithm can then use a stimulation program selected for the patient and the determined directional resistances to determine voltages in the patient's tissue at various locations, which in turn can be used to model a more-accurate electric field in the tissue, and preferably to render an electric field image for display in a graphical user interface of the external device.

Abstract: An architecture is disclosed for an Implantable Pulse Generator having improved compliance voltage monitoring and adjustment software and hardware. Software specifies which stimulation pulses are to be measured as relevant to monitoring and adjusting the compliance voltage. Preferably, specifying such pulses occurs by setting a compliance monitoring instruction (e.g., a bit) in the program that defines the pulse, and the compliance monitor bit instruction may be set at a memory location defining a particular pulse phase during which the compliance voltage should be monitored. When a compliance monitor instruction issues, the active electrode node voltages are monitored and compared to desired ranges to determine whether they are high or low. Compliance logic operates on these high/low signals and processes them to decide whether to issue a compliance voltage interrupt to the microcontroller, which can then command the compliance voltage generator to increase or decrease the compliance voltage.

Abstract: This document discusses, among other things, systems and methods for programming neuromodulation therapy to treat neurological or cardiovascular diseases. A system includes an input circuit that receives a modulation magnitude representing a level of stimulation intensity, a memory that stores a plurality of gain functions associated with a plurality of modulation parameters, and a electrostimulator that may generate and deliver an electrostimulation therapy. A controller may program the electrostimulator with the plurality of modulation parameters based on the received modulation magnitude and the plurality of gain functions, and control the electrostimulator to generate electrostimulation therapy according to the plurality of modulation parameters.