US 6,181,969 B2 · Programmable current output stimulus stage for implantable device

Abstract

A programmable output current source for use within an implantable tissue or nerve stimulator, e.g., an implantable cochlear stimulator or spinal cord stimulator, includes parallel-connected P-FET current source sets connected between a positive voltage rail and an electrode node, and parallel-connected N-FET current source sets connected between the electrode node and a negative voltage rail. The N-FET current source sets include n N-FET current sources, where n is an integer 0, 1, 2, 3, 4, . . . , and wherein each N-FET current source, when enabled, respectively sinks a current 2nI from the electrode node to the negative rail, where I is a selectable fixed current. Similarly, the P-FET current source sets include n P-FET current sources, where n=0, 1, 2, 3, . . . n, and wherein each P-FET current source, when enabled, respectively sources a current 2nI from the positive voltage rail to the electrode node. An individual current pulse is formed by selecting an electrode pair, and enabling a desired combination of P-FET current sources so that a desired total current is sourced to one of the electrodes of the selected electrode pair, and at the same time enabling a corresponding combination of N-FET current sources so that the same total current is sunk from the other electrode of the selected electrode pair. Sequences of current pulses, e.g., biphasic or multiphasic stimulation pulse pairs, are formed by combining individual current pulses having the desired polarity and timing relationship.

Claims20

Dependent claims

A programmable output current circuit for use within an implantable medical device having a plurality of stimulus electrodes, a selected grouping of said stimulus electrodes providing a path through which a programmable stimulus current is selectively applied, each of the plurality of electrodes having an electrode node associated therewith, the programmable output current circuit for each electrode node comprising:

a set of n P-FET current sources, where n is an integer equal to 0, 1, 2, . . . n, wherein each of the n P-FET current sources is permanently attached to the electrode node, and further wherein each of the n P-FET current sources is biased to source a current to the electrode node having a programmable value of 2nI where I is a fixed current reference value;
and
a set of n N-FET current sources, wherein each of the n N-FET current sources is also permanently attached to the electrode node, and further wherein each of the n N-FET current sources is biased to sink a current from the electrode node having a programmable value of 2nI;
and
control means for selectively biasing each of the n P-FET and n N-FET current sources in an enabled or disabled state;
an electrode associated with each electrode node;
wherein a first combination of enabled P-FET current sources, accompanied by a second combination of enabled N-FET current sources, cause a current flow to occur through a load connected between the electrodes associated with the electrode nodes of the respective sets of enabled P-FET and N-FET current sources having a magnitude equal to the sum of all the currents sourced from each of the enabled P-FET current sources, which sum is equal to the sum of all the currents sunk to each of the enabled N-FET current sources.

4 more elements

A programmable output current stage for use within an implantable medical device having a plurality of stimulus electrodes, a selected grouping of said stimulus electrodes providing a path through which a programmable stimulus current is selectively applied to body tissue adjacent the stimulus electrodes, each of the plurality of electrodes having an electrode node associated therewith, the programmable output current stage comprising

a plurality of positive and negative programmable current sources attached to each electrode node, the plurality of positive and negative programmable current sources attached to each electrode node comprising:
a first set of n positive current sources, where n is an integer equal to 0, 1, 2, . . . n, wherein each of the n positive current sources is permanently attached to the electrode node, and further wherein each of the n positive current sources is biased, when enabled, to source a current to the electrode node having a magnitude of 2nI, where I is a fixed current reference value, and
a second set of n negative current sources, wherein each of the n negative current sources is also permanently attached to the electrode node, and further wherein each of the n negative current sources is biased, when enabled, to sink a current from the electrode node having a magnitude of 2nI, and
a respective control line attached to each of the n positive and negative current sources, wherein a control signal applied to the control line enables or disables the current source to which the control line is attached;
and
an electrode associated with each electrode node;
wherein a first combination of enabled positive current sources, accompanied by a second combination of enabled negative current sources, causes a current flow to occur through body tissue adjacent the electrodes associated with the electrode nodes of the enabled positive and negative current sources.

4 more elements

Dependencies are inferred from the claim text.

Programmable current output stimulus stage for implantable device

Life of this patent

Programmable current output stimulus stage for implantable device

Life of this patent

Abstract

Claims20