Hybrid multi-phasic stimulation

1 . A method, comprising:

injecting a charge into tissue of a recipient of an implantable medical device by delivering, via at least one of a plurality of implantable electrodes of the implantable medical device, a stimulation current pulse;

removing a first portion of the charge injected into the tissue by the stimulation current pulse by shorting the at least one of the plurality of implantable electrodes with one or more other of the plurality of implantable electrodes; and

removing a second portion of the charge injected into the tissue by the stimulation current pulse by delivering at least one discharging current pulse to the tissue of the recipient after shorting the at least one of the plurality of implantable electrodes with the one or more other of the plurality of implantable electrodes.

2 . The method of claim 1 , comprising delivering a first discharging current pulse to the tissue prior to shorting the at least one of the plurality of implantable electrodes with the one or more other of the plurality of implantable electrodes, wherein delivering the at least one discharging current pulse to the tissue comprises delivering a second discharging current pulse to the tissue after shorting the at least one of the plurality of implantable electrodes with the one or more other of the plurality of implantable electrodes.

3 . The method of claim 1 , wherein the stimulation current pulse has a first current polarity and the at least one discharging current pulse has second current polarity, wherein the second current polarity is an opposite current polarity to the first current polarity.

4 . The method of claim 1 , wherein removing the first portion of the charge injected into the tissue by the stimulation current pulse by shorting the at least one of the plurality of implantable electrodes with the one or more other of the plurality of implantable electrodes comprises:

shorting all of the plurality of implantable electrodes together to a common point of the implantable medical device via one or more low impedance paths.

5 . The method of claim 1 , wherein removing the first portion of the charge injected into the tissue by the stimulation current pulse by shorting the at least one of the plurality of implantable electrodes with the one or more other of the plurality of implantable electrodes comprises:

during the shorting, controlling a flow of current from the tissue to a common point of the implantable medical device via one or more low impedance paths.

6 . The method of claim 5 , wherein the at least one of the plurality of implantable electrodes and the one or more other of the plurality of implantable electrodes are each connected to the common point via a corresponding one of a plurality of switches and corresponding one of a plurality of resistor elements.

7 . The method of claim 6 , wherein the plurality of resistor elements comprise a plurality of variable resistor elements, and wherein controlling the flow of current from the tissue to the common point of the implantable medical device comprises:

adjusting, over time, a resistance value of one or more of the plurality of variable resistor elements.

8 . The method of claim 1 , wherein the stimulation current pulse and the at least one discharging current pulse are unbalanced.

9 . The method of claim 1 , further comprising:

determining one or more attributes of the at least one discharging current pulse controlling the second portion of the charge removed from the tissue based, at least in part, on impedances of the plurality of implantable electrodes.

10 . The method of claim 1 , further comprising:

measuring an instantaneous voltage at the tissue after the shorting of the at least one of the plurality of implantable electrodes with the one or more other of the plurality of implantable electrodes; and

dynamically determining one or more attributes of the at least one discharging current pulse controlling the second portion of the charge removed from the tissue based, at least in part, on the instantaneous voltage at the tissue after the shorting of the at least one of the plurality of implantable electrodes with the one or more other of the plurality of implantable electrodes.

11 . The method of claim 10 , further comprising:

measuring an instantaneous voltage at the tissue after the stimulation current pulse is injected into the tissue; and

dynamically determining the one or more attributes of the at least one discharging current pulse controlling the second portion of the charge removed from the tissue based, at least in part, on the instantaneous voltage at the tissue after the stimulation current pulse is injected into the tissue and the instantaneous voltage at the tissue after the shorting of the at least one of the plurality of implantable electrodes with the one or more other of the plurality of implantable electrodes.

12 . The method of claim 1 , further comprising:

providing an Inter Phase Gap from the stimulation current pulse to the shorting of the at least one of the plurality of implantable electrodes with the one or more other of the plurality of implantable electrodes.

13 . An implantable medical device, comprising:

a stimulation subsystem configured to generate a stimulation current pulse;

a plurality of implantable electrodes configured to be implanted adjacent to tissue of a recipient of the implantable medical device, wherein at least one of the plurality of implantable electrodes is configured to deliver the stimulation current pulse to inject charge into the tissue of the recipient; and

a plurality of switches configured to short the at least one of the plurality of implantable electrodes with one or more other of the plurality of implantable electrodes to remove a first portion of the charge injected into the tissue by the stimulation current pulse,

wherein the stimulation subsystem is configured to generate at least one discharging current pulse for delivery to the tissue of the recipient to remove a second portion of the charge injected into the tissue by the stimulation current pulse, wherein the stimulation subsystem is configured to close one or more of the plurality of switches to short the at least one of the plurality of implantable electrodes with the one or more other of the plurality of implantable electrodes after generating the stimulation current pulse and provide an Inter Phase Gap from the stimulation current pulse to shorting of the at least one of the plurality of implantable electrodes, and wherein no current is delivered to or withdrawn from the plurality of implantable electrodes during the Inter Phase Gap.

14 . The implantable medical device of claim 13 , wherein the at least one discharging current pulse comprises a plurality of discharging current pulses collectively configured to remove the second portion of the charge injected into the tissue by the stimulation current pulse.

15 . The implantable medical device of claim 13 , wherein the stimulation current pulse has a first current polarity and the at least one discharging current pulse has a second current polarity, wherein the second current polarity is an opposite current polarity to the first current polarity.

16 . The implantable medical device of claim 13 , wherein the stimulation subsystem is configured to close the one or more of the plurality of switches to short the at least one of the plurality of implantable electrodes with the one or more other of the plurality of implantable electrodes to a common point.

17 . A method, comprising:

delivering, via at least one of a plurality of implantable electrodes of an implantable medical device, a stimulation current pulse to inject charge into tissue of a recipient of the implantable medical device;

shorting the at least one of the plurality of implantable electrodes with one or more other of the plurality of implantable electrodes to remove a first portion of the charge injected into the tissue by the stimulation current pulse;

measuring an instantaneous voltage at the tissue after the shorting of the at least one of the plurality of implantable electrodes with the one or more other of the plurality of implantable electrodes;

dynamically determining one or more attributes of at least one discharging current pulse controlling a second portion of the charge removed from the tissue based, at least in part, on the instantaneous voltage at the tissue after the shorting of the at least one of the plurality of implantable electrodes with the one or more other of the plurality of implantable electrodes; and

delivering the at least one discharging current pulse to the tissue of the recipient to remove the second portion of the charge injected into the tissue by the stimulation current pulse.

18 . The method of claim 17 , comprising providing an Inter Phase Gap from the stimulation current pulse to the shorting of the at least one of the plurality of implantable electrodes with the one or more other of the plurality of implantable electrodes, wherein no current is delivered to or withdrawn from the plurality of implantable electrodes during the Inter Phase Gap.

19 . The method of claim 17 , wherein the stimulation current pulse and the at least one discharging current pulse are unbalanced and of opposite polarity.