U.S. patent application number 13/647200 was filed with the patent office on 2013-05-16 for external charger for an implantable medical device system having a coil for communication and charging.
This patent application is currently assigned to Boston Scientific Neuromodulation Corporation. The applicant listed for this patent is Boston Scientific Neoromodulation Corporation. Invention is credited to Daniel Aghassian.
Application Number | 20130123881 13/647200 |
Document ID | / |
Family ID | 48281349 |
Filed Date | 2013-05-16 |
United States Patent
Application |
20130123881 |
Kind Code |
A1 |
Aghassian; Daniel |
May 16, 2013 |
External Charger for an Implantable Medical Device System Having a
Coil for Communication and Charging
Abstract
Disclosed in an improved medical implantable device system
including an improved external charger that is able to communicate
with an external controller and IPG using the communication
protocol (e.g., FSK) used to implement communications between the
external controller and the implant. The external controller as
modified uses its charging coil to charge the implant, and also to
communicate with the other devices in the system. As such, the
external charger is provided with transceiver circuitry operating
in accordance with the protocol, and also includes tuning circuitry
to tune the coil as necessary for communications or charging.
Communication or charging access to the charging coil in the
external charger is time multiplexed. The disclosed system allows
charging information to be provided to the user interface of the
external controller so that it can be reviewed by the user, who may
take corrective action if necessary. Also disclosed are schemes for
synchronizing and arbitrating communications between the devices in
the system.
Inventors: |
Aghassian; Daniel;
(Glendale, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Boston Scientific Neoromodulation Corporation; |
Valencia |
CA |
US |
|
|
Assignee: |
Boston Scientific Neuromodulation
Corporation
Valencia
CA
|
Family ID: |
48281349 |
Appl. No.: |
13/647200 |
Filed: |
October 8, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61558601 |
Nov 11, 2011 |
|
|
|
Current U.S.
Class: |
607/61 |
Current CPC
Class: |
A61N 1/37247 20130101;
A61N 1/3787 20130101; A61N 1/37223 20130101; A61N 1/37235 20130101;
A61N 1/37252 20130101 |
Class at
Publication: |
607/61 |
International
Class: |
A61N 1/00 20060101
A61N001/00 |
Claims
1. A method for operating an implantable medical device system,
comprising: charging an implantable medical device with a charging
field generated from a coil in an external charger; establishing a
first communication link for telemetry between the coil in the
external charger and the external controller, wherein access to the
coil in the external charger for the acts of charging and
establishing the first communication link is time domain
multiplexed.
2. The method of claim 1, further comprising sending charging
information from the external charger to the external controller
via the first communication link.
3. The method of claim 2, further comprising conveying the charging
information to a user via a user interface of the external
controller.
4. The method of claim 3, wherein the user interface is a graphical
user interface.
5. The method of claim 2, wherein the charging information
comprises one or more of: information concerning the alignment
between the external charger and the implantable medical device;
status of a battery of the implantable medical device; status of a
battery of the external charger; and the temperature of either the
external charger or the implantable medical device.
6. The method of claim 2, wherein the charging information is sent
in accordance with a plurality of data transit modes.
7. The method of claim 2, wherein the charging information
determines the frequency with which the charging information is
sent from the external charger to the external controller.
8. The method of claim 2, wherein the charging information is sent
more frequently when the external charger is misaligned with the
implantable medical device.
9. The method of claim 2, wherein the charging information
comprises alignment information between the external charger and
the implantable medical device.
10. The method of claim 9, further comprising displaying alignment
information to a user via a graphical user interface on the
external controller.
11. The method of claim 1, further comprising establishing a second
communication link between the external charger and the implantable
medical device, wherein access to the coil in the external charger
for the acts of charging, establishing the first communication
link, and establishing the second communication link is time domain
multiplexed.
12. The method of claim 11, wherein the first and second
communication links are established in accordance with the same
protocol.
13. The method of claim 11, further comprising receiving charging
information from the external charger and from the implantable
medical device over the second communication link; and sending the
charging information from the external charger to the external
controller via the first communication link.
14. The method of claim 1, wherein the external controller and the
implantable medical device communicate via a protocol, and wherein
the first communication link is established in accordance with the
protocol.
15. An implantable medical device system, comprising: an external
controller for communicating with an implantable medical device;
and an external charger comprising a coil, the coil configured to
generate a charging field for providing energy to the implantable
medical device and to communicate with the external controller via
a first communication link.
16. The system of claim 15 wherein the external charger further
comprises a tuning circuit coupled to the coil, wherein the tuning
circuit is configured to tune the coil to a first frequency for
generating the charging field and a second frequency for
communicating with the external controller via a first
communication link.
17. The system of claim 16, wherein the coil is further configured
to communicate with the implantable medical device via a second
communication link, wherein the tuning circuit is configured to
tune the coil to the second frequency for communicating with the
implantable medical device via the second communication link.
18. The system of claim 15, wherein the external charger
communicates charging information to the external controller over
the first communication link.
19. The system of claim 18, wherein the external controller
comprises a user interface for conveying the charging information
to a user.
20. The system of claim 19, wherein the user interface is
graphical.
21. The system of claim 20, wherein the implantable medical device
comprises an implant battery, and wherein the charging information
comprises an implant battery level.
22. The system of claim 15, wherein the first communication link
uses a protocol used by the external controller for communicating
with the implantable medical device.
23. The system of claim 22, wherein the communication protocol
comprises a frequency shift keying (FSK) protocol.
24. An implantable medical device system, comprising: an external
charger comprising a coil, the coil configured to generate a
charging field for providing energy to an implantable medical
device; and an external controller configured for communicating
with the implantable medical device, wherein the external
controller is further configured for communicating with the coil in
the external charger via a first communication link to control the
operation of the external charger.
25. The system of claim 24, wherein the external controller
controls the external charger by instructing the external charger
to begin generating the charging field.
26. The system of claim 24, wherein the external controller
controls the external charger by instructing the external charger
to stop generating the charging field.
27. The system of claim 26, wherein the external controller is
configured to communicate with the implantable medical device after
the external charger has stopped generating the charging field.
28. The system of claim 27, wherein the external controller is
configured to communicate therapy settings to the implantable
medical device.
29. The system of claim 28, wherein the external controller further
controls the external charger by instructing the external charger
to restart generating the charging field after the external
controller has completed communicating with the implantable medical
device.
30. The system of claim 24, wherein the external controller
controls the external charger by instructing the external charger
to send charging information to the external controller.
31. The system of claim 30, wherein the external controller
comprises a user interface for conveying charging information
received from the external charger to a user.
32. The system of claim 24, wherein the coil in the external
charger is further configured to communicate with the implantable
medical device via a second communication link.
33. The system of claim 32, wherein the external charger is
configured to instruct the implantable medical device to send
charging information to the external charger via the second
communication link.
34. A method for operating an implantable medical device system,
comprising: compiling, at an external controller, information to be
sent to an implantable medical device; sending a first
communication using a protocol from the external controller to an
external charger, the first communication instructing the external
charger to turn off a charging field; and thereafter sending the
compiled information from the external controller to the
implantable medical device using the protocol.
35. The method of claim 34, wherein the information includes a
therapy setting.
36. The method of claim 35, wherein the therapy setting comprises
one or more of: a status inquiry; a wake up message; a power down
message; a stimulation on/off message; a level or an amplitude of
stimulation pulses; a duration or a frequency of stimulation
pulses; or a selection of electrodes to be activated.
37. The method of claim 34, further comprising sending a second
communication using the protocol after sending the compiled
information, the second communication instructing the external
charger to turn on the charging field.
38. The method of claim 34, wherein the external charger includes a
coil for receiving the first communication and for generating the
charging field.
39. The method of claim 34, wherein the protocol comprises
frequency shift keying.
40. A method for operating an implantable medical device system,
comprising: sending a first communication, using a protocol, from
an external controller to an external charger to cease an operation
between the external charger and an implantable medical device;
transmitting data between the external controller and the
implantable medical device using the protocol; and sending a second
communication, using the protocol, from the external controller to
the external charger to allow resumption of the operation between
the external charger and the implantable medical device.
41. The method of claim 40, wherein the operation includes charging
the implantable medical device using a charging field.
42. The method of claim 40, wherein the operation includes
requesting charging information from the implantable medical
device.
43. The method of claim 40, wherein transmitting data includes
sending a therapy setting from the external controller to the
implantable medical device.
44. The method of claim 43, wherein the therapy setting comprises
one or more of: a status inquiry; a wake up message; a power down
message; a stimulation on/off message; a level or an amplitude of
stimulation pulses; a duration or a frequency of stimulation
pulses; or a selection of electrodes to be activated.
45. The method of claim 40, wherein the external charger includes a
coil for sending the first and the second communications and for
enabling the operation with the implantable medical device.
46. The method of claim 40, wherein the protocol includes frequency
shift keying.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a non-provisional of U.S. Provisional Patent
Application Ser. No. 61/558,601, filed Nov. 11, 2011, which is
incorporated herein by reference, and to which priority is
claimed.
FIELD OF THE INVENTION
[0002] The present invention relates to an improved implantable
medical device system having a communication link between an
external controller and an external charger.
BACKGROUND
[0003] Implantable stimulation devices are devices that generate
and deliver electrical stimuli to nerves and tissues for the
therapy of various biological disorders, such as pacemakers to
treat cardiac arrhythmia, defibrillators to treat cardiac
fibrillation, cochlear stimulators to treat deafness, retinal
stimulators to treat blindness, muscle stimulators to produce
coordinated limb movement, spinal cord stimulators to treat chronic
pain, cortical and deep brain stimulators to treat motor and
psychological disorders, and other neural stimulators to treat
urinary incontinence, sleep apnea, shoulder sublaxation, etc. The
description that follows will generally focus on the use of the
invention within a Spinal Cord Stimulation (SCS) system, such as
that disclosed in U.S. Pat. No. 6,516,227. However, the present
invention may find applicability in any implantable medical device
system. For example, the disclosed invention can also be used with
a Bion.TM. implantable stimulator, such as is shown in U.S. Patent
Publication 2007/0097719, or with other implantable medical
devices.
[0004] As shown in FIGS. 1A and 1B, a SCS system typically includes
an Implantable Pulse Generator (IPG) 100, which includes a
biocompatible device case 30 formed of titanium for example. The
case 30 typically holds the circuitry and battery 26 necessary for
the IPG to function, although IPGs can also be powered via external
RF energy and without a battery. The IPG 100 is coupled to
electrodes 106 via one or more electrode leads (two such leads 102
and 104 are shown), such that the electrodes 106 form an electrode
array 110. The electrodes 106 are carried on a flexible body 108,
which also houses the individual signal wires 112 and 114 coupled
to each electrode. In the illustrated embodiment, there are eight
electrodes on lead 102, labeled E.sub.1-E.sub.8, and eight
electrodes on lead 104, labeled E.sub.9-E.sub.16, although the
number of leads and electrodes is application specific and
therefore can vary. The leads 102 and 104 couple to the IPG 100
using lead connectors 38a and 38b, which are fixed in a header
material 36, which can comprise an epoxy for example. In a SCS
application, electrode leads 102 and 104 are typically implanted on
the right and left side of the dura within the patient's spinal
cord. These leads 102 and 104 are then tunneled through the
patient's flesh to a distant location, such as the buttocks,
wherein the IPG 100 is implanted.
[0005] As shown in cross section in FIG. 3, the IPG 100 typically
includes an electronic substrate assembly 14 including a printed
circuit board (PCB) 16, along with various electronic components
20, such as a microcontroller, integrated circuits, and capacitors
mounted to the PCB 16. Two coils are generally present in the IPG
100: a telemetry coil 13 used to transmit/receive data to/from an
external controller 12; and a charging coil 18 for charging or
recharging the IPG's battery 26 using an external charger 50. The
telemetry coil 13 can be mounted within the header 36 of the IPG
100 as shown.
[0006] FIG. 2 shows plan views of the external controller 12 and
the external charger 50, and FIG. 3 shows these external devices in
cross section and in relation to the IPG 100 with which they
communicate. The external controller 12, such as a hand-held
programmer or a clinician's programmer, is used to send data to and
receive data from the IPG 100. For example, the external controller
12 can send programming data such as therapy settings to the IPG
100 to dictate the therapy the IPG 100 will provide to the patient.
Also, the external controller 12 can act as a receiver of data from
the IPG 100, such as various data reporting on the IPG's status. As
shown in FIG. 3, the external controller 12, like the IPG 100, also
contains a PCB 70 on which electronic components 72 are placed to
control operation of the external controller 12. The external
controller 12 is powered by a battery 76, but could also be powered
by plugging it into a wall outlet for example. A telemetry coil 73
is also present in the external controller 12, which coil will be
discussed further below.
[0007] The external controller 12 typically comprises a user
interface 74 similar to that used for a portable computer, cell
phone, or other hand held electronic device. The user interface 74
typically comprises touchable buttons 80 and a display 82, which
allows the patient or clinician to send therapy programs to the IPG
100, and to review any relevant status information reported from
the IPG 100.
[0008] Wireless data transfer between the IPG 100 and the external
controller 12 preferably takes place via inductive coupling. This
typically occurs using a well-known Frequency Shift Keying (FSK)
protocol, in which logic `0` bits are modulated at a first
frequency (e.g., 121 kHz), and logic `1` bits are modulated at a
second frequency (e.g., 129 kHz). To implement such communications,
both the IPG 100 and the external controller 12 have coils 13 and
73 respectively. Either coil can act as the transmitter or the
receiver, thus allowing for two-way communication between the two
devices. Referring to FIG. 4, when data is to be sent from the
external controller 12 to the IPG 100 (FSK link 170), coil 73 is
energized with alternating current (AC), which generates a magnetic
field, which in turn induces a voltage in the IPG's telemetry coil
13. The generated magnetic field is FSK modulated (120) in
accordance with the data to be transferred. The induced voltage in
coil 13 can then be FSK demodulated (125) at the IPG 100 back into
the telemetered data signals. Data telemetry in the opposite
direction (FSK link 172) from IPG 100 to external controller 12
occurs similarly. This means of communicating by inductive coupling
is transcutaneous, meaning it can occur through the patient's
tissue 25.
[0009] The external charger 50 is used to charge (or recharge) the
IPG's battery 26. Specifically, and similarly to the external
controller 12, the external charger 50 contains a coil 88 which is
energized via charging circuit 122 with a non-modulated AC current
to create a magnetic charging field (174). This magnetic field
induces a current in the charging coil 18 within the IPG 100, which
current is rectified (132) to DC levels, and used to recharge the
battery 26, perhaps via a charging and battery protection circuit
134 as shown. The frequency of the magnetic charging field (e.g.,
80 kHz) may differ from that used for FSK telemetry (nominally 125
kHz). Again, inductive coupling of power in this manner occurs
transcutaneously.
[0010] The IPG 100 can also communicate data back (176) to the
external charger 50 using Load Shift Keying (LSK) modulation
circuitry 126. LSK modulation circuitry 126 receives data to be
transmitted back to the external charger 50 from the IPG's
microcontroller 150, and then uses that data to modulate the
impedance of the charging coil 18. In the illustration shown,
impedance is modulated via control of a load transistor 130, with
the transistor's on-resistance providing the necessary modulation.
This change in impedance is reflected back to coil 88 (LSK link
176) in the external charger 50, which interprets the reflection at
LSK demodulation circuitry 123 to recover the transmitted data.
This means of transmitting data from the IPG 100 to the external
charger 50 is useful to communicate data relevant to charging of
the battery 26 in the IPG 100, such as the battery level, whether
charging is complete and the external charger can cease, and other
pertinent charging variables. However, because LSK works on a
principle of reflection, such data can only be communicated from
the IPG 100 to the external charger 50 during periods in which the
external charger 50 is active and is producing a magnetic charging
field (174).
[0011] As shown in FIG. 3, the external charger 50 generally
comprises at least one printed circuit board 90, electronic
components 92 which control operation of the external charger 50,
and a battery 96 for providing operational power for the charger 50
and for the production of the magnetic charging field. Like the
external controller 12, the external charger 50 has a user
interface 94 to allow the patient or clinician to operate the
charger 50. The user interface 94 typically comprises an on/off
switch 95 which activates the production of the magnetic charging
field; an LED 97 to indicate the status of the on/off switch 95;
and a speaker 98 for emitting a "beep" at various times. For
example, the speaker 98 can beep if the charger 50 detects that its
coil 88 is not in good alignment with the charging coil 18 in the
IPG 100. Alignment information can be determined and indicated to
the external charger 252 by alignment circuitry 103, which is
well-known in the art. In a SCS application in which the IPG 100 is
implanted in the patient's buttocks, the external charger 50 is
generally positioned behind the patient and held against the
patient's skin or clothes and in good alignment with the IPG 100 by
a belt or an adhesive patch, which allows the patient some mobility
while charging.
[0012] As one might appreciate from the foregoing description, the
user interface 94 of the external charger 50 is generally simpler
than the user interface 74 of the external controller 12. Such user
interface simplicity is understandable for at least two reasons.
First is the relative simplicity of the charging function the
external charger 50 provides. Second, a complicated user interface,
especially one having visual aspects, may not be warranted because
the external charger 50 may not be visible to the patient when it
is used. For example, in a SCS application, the external charger 50
would generally be behind the patient to align properly with the
IPG 100 implanted in the buttocks as just discussed. The external
charger 50 would not be visible in this position, and thus
providing the user interface 94 of the external charger 50 with a
display or other visual indicator would be of questionable benefit.
Additionally, the external charger 50 may be covered by clothing,
again reducing the utility of any visual aspect to the user
interface.
[0013] Although the simplicity of the user interface 94 of the
external charger 50 is understandable, the inventor still finds
such simplicity regrettable. Even if operation of the external
charger 50 is relatively simple, the fact remains that several
pieces of information relevant to the charging process might be of
interest to the patient, which charging information is impractical
or impossible to present by audible means such as through speaker
98.
[0014] For example, it may be desired for the user to have some
information concerning the alignment between the external charger
50 and the IPG 100; the status of the IPG's battery 26, i.e., to
what level it is charged; how much longer charging might take; the
status of the external charger's battery 96; or the temperature of
either the external charger 50 or the IPG 100. Temperature
information can be particularly important to know for safety
reasons, and can be provided by a thermocouple 101 in the external
charger, and a thermocouple in the IPG (not shown). Inductive
charging can heat both the external charger 50 and the IPG 100, and
if temperatures are exceeding high, injury or tissue damage can
result. Regardless, despite the importance of such charging
information, the user interface 94 does not present such
information to the user.
[0015] One approach in overcoming these shortcomings is disclosed
in U.S. Patent Publication 2010/0305663 ("the '663 Publication"),
filed Jun. 2, 2009, and incorporated herein by reference in its
entirety. As shown in FIG. 5, the '663 Publication provides an RF
communication link 210 between the external charger 50 and the
external controller 12 so that they can communicate with each
other. RF communication link 210 is enabled by an RF transceiver
202 and an RF antenna 202a in the external controller 12, and a
corresponding RF transceiver 200 and antenna 200a in the external
charger 50. Link 210 preferably comprises a Bluetooth.TM. compliant
link, or other suitable RF communications protocol such as
Zigbee.TM., WiFi, etc.
[0016] The external charger 50 and the IPG 100 can generate a
variety of charging information such as those parameters just
mentioned that can be transmitted to the external controller 12,
where it can be reviewed and controlled by the external
controller's 12 user interface 74, which as noted is more
sophisticated and easier to view. For example, using RF
communication link 210, the user can review the relevant charging
information from the external charger 50. Relevant charging
information from the IPG 100 such as battery 26 status and
temperature can be transmitted via LSK link 176 to the external
charger 50, and then sent to the external controller 12 via the RF
communication link 210, or could be sent directly to the external
controller 12 via FSK link 172. FIG. 6 shows the user interface 74
of the external controller 12 displaying such charging information
232 on its display 82. Some processing of the charging information
may occur first in the external controller 12 before it is
presented in this manner.
[0017] While the system of the '662 Publication provides desirable
versatility, the inventors recognize a few drawbacks. For example,
the system adds additional hardware components to the external
charger 50 and the external controller 12 such as transceivers 200
and 202, antennas 200a and 202a, etc. This additional hardware adds
cost, in terms of power and expense, and complexity to the
system.
[0018] Given these shortcomings, the art of implantable medical
devices would benefit from an improved means for providing relevant
charging information to a patient, and this disclosure presents
solutions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIGS. 1A and 1B show an implantable pulse generator (IPG),
and the manner in which an electrode array is coupled to the IPG in
accordance with the prior art.
[0020] FIG. 2 shows plan views of an external controller and an
external charger which communicate with an IPG in accordance with
the prior art.
[0021] FIG. 3 shows cross sectional views of the external
controller, the external charger and the IPG of FIGS. 1 and 2, and
shows the communicative relations between these devices.
[0022] FIGS. 4 and 5 show communication circuitry present in the
external controller, the external charger, and the IPG in
accordance with the prior art.
[0023] FIG. 6 shows the user interface of the external controller,
and how that interface can display charging information in
accordance with the prior art.
[0024] FIG. 7 shows an improved system in which the external
controller and the external charger establish a communication link
by using the charging coil of the external charger in accordance
with an embodiment of the present invention.
[0025] FIG. 8 shows additional details of the external charger of
FIG. 7 in accordance with an embodiment of the present
invention.
[0026] FIGS. 9A-9D show time-domain-multiplexed communications
between the external charger, the external controller and the IPG
of the system of FIG. 7 in accordance with an embodiment of the
present invention.
DETAILED DESCRIPTION
[0027] The description that follows relates to use of the invention
within a spinal cord stimulation (SCS) system. However, it is to be
understood that the invention is not so limited. Rather, the
invention may be used with any type of implantable medical device
system. For example, the present invention may be used in a system
employing an implantable sensor, an implantable pump, a pacemaker,
a defibrillator, a cochlear stimulator, a retinal stimulator, a
stimulator configured to produce coordinated limb movement, a
cortical and deep brain stimulator, or in any other neural
stimulator system configured to treat any of a variety of
conditions.
[0028] Disclosed is an improved medical implantable device system
including an improved external charger that is able to communicate
with an external controller and IPG using the communication
protocol (e.g., FSK) used to implement communications between the
external controller and the implant. The external charger as
modified uses its charging coil to charge the implant as is normal,
and also to communicate with the other devices in the system. As
such, the external charger is provided with transceiver circuitry
operating in accordance with the protocol, and also includes tuning
circuitry to tune the coil as necessary for communications or
charging.
[0029] Communication or charging access to the charging coil in the
external charger is time multiplexed. The disclosed system allows
charging information to be provided to the user interface of the
external controller so that it can be reviewed by the user, who may
take corrective action if necessary. Also disclosed are schemes for
synchronizing and arbitrating communications between the devices in
the system.
[0030] FIG. 7 discloses an embodiment of the improved system 201,
which system comprises an IPG 100, an improved external charger
252, and an improved external controller 254. Unlike
previously-known approaches which use separate antennas and
transceiver circuits for communicating data between the external
charger and the external controller, the improved system 201 uses
the charging coil 88 in the external charger 252 for communicating
data to the external controller 254 via link 251. Link 251
preferably operates in accordance with the same protocol that is
used by communication links 170 and 172 between the external
controller 254 and the IPG 100, e.g., FSK. Additionally, because
the coil 88 in the external charger 252 is FSK compliant, it may
additionally communicate with the IPG 100 via an FSK link 266.
Rendering the external charger 50 to be FSK compliant in this
fashion requires only minimal changes to the external charger 50,
and requires no hardware changes to either the external controller
254 or the IPG 100. Moreover, and as will be seen below, improving
the communicative flexibility between these devices in system 201
allows charging information to be easily sent to the external
controller 254, where such data can be processed and presented to
the user interface 74 of the external controller.
[0031] Legacy communications in system 201 remain unaffected. Thus,
the external controller 254 and IPG 100 can still communicate via
FSK via data links 170 and 172. And the external charger 252 can
still provide a magnetic charging field (174) to the IPG 100.
Moreover, the IPG 100 can still communicate data back to the
external charger 252 via LSK, and as such the external charger 252
can still include LSK demodulation circuitry 123 (FIG. 4) if
desired, although this is not shown in FIG. 7. As will be seen,
there is less, or no, need in system 201 for LSK telemetry given
the preferred use of FSK link 266 to communicate between the
external charger 252 and the IPG 100.
[0032] The external charger 252 is modified in FIG. 7 to include a
transceiver circuit 255, which includes a FSK modulator circuit
265, and a FSK demodulator circuit 256. The FSK modulator and
demodulator circuits 265 and 256 can be similar to the FSK
modulator and demodulator circuits 120 and 121 of the external
controller 254. The external charger 252 also includes a tuning
circuit 253 for tuning the coil 88 appropriately for both charging
and FSK telemetry.
[0033] FIG. 8 illustrates the external charger 252 in further
detail. Tuning circuit 253 includes charging capacitor Cch 259, a
data capacitor Cdt 257, and a switch 258 controlled by a control
signal K1 issued form the external charger's microcontroller 144.
The series combination of the switch 258 and Cch 259 is connected
in parallel with Cdt 257. Switch 258 can take one of two positions:
open/off when the external charger 252 is being used to telemeter
or receive data, and closed/on when it is being used to charge the
IPG 100. When switch 258 is open during telemetry, Cch 259 is
disconnected from the coil 88 resulting in a series resonant tank
circuit formed by the coil 88 and Cdt 257 which resonates at a
frequency suitable for FSK telemetry, e.g., 125 kHz. When switch
258 is closed, Cch 259 appears in parallel with Cdt 257, increasing
the effective capacitance in series with coil 88 and lowering the
frequency to that suitable for charging, e.g., 80 kHz.
[0034] Microcontroller 144 in the external charger 252 also
controls charge circuit 122 and transceiver circuitry 255 at
appropriate times, depending on whether charging or telemetry is
taking place. For example, microcontroller 144 can turn off the
charging circuit 122 or put it in high impedance state during data
telemetry or during periods when the external charger 252 is
listening for an incoming data transmission so that the charging
circuit 122 does not load or affect the transceiver circuit 255.
Likewise, the microcontroller 144 can turn off the transceiver
circuit 255 or put it in high impedance state so that it does not
load or affect the charging circuit 122 during charging. Although
not shown, control signal K1 can also be received by charging
circuitry 122 and transceiver circuitry 255 to inform those modules
what mode (telemetry or charging) the external charger is operating
in, and to respond appropriately.
[0035] While the external charger 252 is capable of carrying out
data communication with the external controller 254, its primary
purpose is to charge the IPG 100. Time spent by the external
charger 252 in communicating with the external controller 254 or
the IPG 100 is time spent not charging the IPG 100, which can
result in longer charging times. Therefore, the external charger
252 is designed to maximize the amount of time spent charging the
IPG 100, and only intermittently discontinues charging to
communicate with the external controller 254 or the IPG 100 when
necessary, as will be seen.
[0036] The external charger 252 can alternate between communicating
telemetry data with the external controller 254 and charging the
IPG 100 using two modes of operation: a fast data transmit mode,
and a slow data transmit mode. The fast data transmit mode is
particularly useful when the external charger 252 needs to provide
near real-time charging information to the external controller 254.
One example of this would be when the external charger 252 needs to
provide alignment data to inform the user about the position of the
external charger 252 relative to the IPG 100. It is desired to
display such information relatively quickly on the display 82 of
the external controller 254 so that the user can take quick
corrective action in repositioning the external charger 252 if
necessary. By contrast, other charging information, such as battery
level, or alignment information once initial good alignment has
been achieved, need not be presented at the external controller 254
as quickly, and instead this data can be uploaded to the external
controller 254 in the slow data transit mode with less frequency
and with some latency, which is less disruptive of charging.
[0037] FIGS. 9A-9D illustrate timing diagrams to further describe
the operation of system 201, and discusses in detail the data
transit modes just mentioned as well as other means of effecting
communications between the external charger 252, the external
controller 254, and the IPG 100. The timings illustrated in the
Figures can be implemented and controlled by programming of the
microcontrollers 144, 142, and 150 respectively in the external
charger 252, the external controller 254, and the IPG 100. It
should be noted that the various communication shown in FIGS. 9A-9D
occur by FSK, either via FSK link 251 between the external charger
252 and the external controller 254, or link 266 between the
external charger 252 and the IPG 100. Time-multiplexed access to
the coil 88 in the external charger 252, and appropriate enablement
of the charging circuitry 122, the FSK transceiver circuitry 255,
and tuning circuitry 253, would occur as previously described.
Timings for the various periods shown in FIGS. 9A-9D are shown at
the bottom of each figure, but these are merely non-limiting
examples. Timing may not be drawn to scale.
[0038] In the depicted example of the system 201, the external
controller 254 takes precedence over the external charger 252, and
can control the external charger 252 such as by turning the charger
on or off, or requesting information from the charger as necessary.
It is beneficial to arbitrate communications in this way because
the charging field created by the external charger 252 (174, FIG.
7) can interfere with FSK communications. As such, when the
external controller 254 wishes to communicate with either the
external charger 252 or the IPG 100, the controller notifies the
charger of that fact so that the charger can temporarily suspend
production of the charging field.
[0039] As a result, the external charger 252 must periodically
listen for communications from the external controller 254, as is
shown starting in FIG. 9A. In FIG. 9A, the external charger 252 is
operating as it does in a normal legacy system to provide a
charging field. Thus, the patient has turned on the external
charger 252 to produce a charging field to charge the battery 26 in
the IPG 100. Such charging occurs during charging periods CF 401,
which may last for a duration of 190 ms for example. Interspersed
between these periods CF are listening windows LW 407, during which
the external charger 252 listens for telemetry from external
controller 254, which is not presently operating in FIG. 9A. The
duration of the listening windows LW 407 may be 10 ms long in one
example, which is small in comparison to the duration of the
charging fields. Therefore, while the listening windows LW 407
increase the overall time needed to charge the battery 26 in the
IPG 100, such interruptions are small, and generally transparent to
the patient.
[0040] Eventually, the patient may turn off the external charger
252, or the charger may suspend charging per its normal operation
when notified (by LSK telemetry for example) the battery 26 is
fully charged, as shown by the absence of charging periods CF at
the right side of FIG. 9A. At this point, the external charger 252
is in a power-down (low power, or sleep) state, but still
periodically listens for telemetry from the external controller
254. Keeping the external charger 252 in a power-down state is
reasonable given the relative large battery 96 (FIG. 3) within the
charger. Once the external charger 252 is no longer producing a
charging field, the spacing 414 between the listening windows LW
407 can be increased significantly to save power. Moreover, all the
while, the IPG 100 has also been listening for telemetry requests
during listening windows 415, as it does in legacy systems.
[0041] FIG. 9B illustrates use of the external controller 254 to
receive charging information of the types previously discussed.
Providing charging information to the external controller 254 can
commence at any reasonable time during operation of the external
controller 254, such as when the patient accesses an appropriate
menu to review such information, as shown in FIG. 6 for example.
Regardless of how or when this occurs, the external controller 254
transmits a first command TC1 to the external charger 252 along
link 251 (FIG. 7), which in effect starts a "handshaking" procedure
between the controller and charger. Prior to this, the external
charger 252 may have been in the power-down state, or may have
already been providing a charging field, as shown by the dotted
line around period 401 at the left of FIG. 9B. If powered down, the
external controller 254 will eventually turn on the external
charger 252 so that it can produce a charging field and thus
provide the charging information of interest, as will be seen
shortly.
[0042] This first command TC1 requests an acknowledgment AK 306
from the charger 252, and alerts the external charger 252 to begin
listening for further commands. The duration of TC1 is typically
long enough to coincide with one of the external charger's
listening windows LW, such as LW 407a in the illustrated example,
and is repeated to ensure that it can be fully received during a
window LW 407. The TC1 command can include in one example 19 bytes
of alerting code recognizable by the external charger 252, 3 bytes
of containing the device ID of the charger 252, 1 byte of command
(in this case, requesting an acknowledgment), and two bytes of
error checking code (e.g., Cyclic Redundancy Check (CRC) data). The
device ID ensures that the proper device in the system--external
charger 252--will respond as opposed to the IPG 100 or some other
external charger or other external device.
[0043] The external charger 252 acknowledges receiving command TC1
with an acknowledgment AK 306, which is received at the external
controller 254 during duration RX 303. AK 306 can also by default
include status information, including the charging information, or
such information may come later after handshaking The external
controller 254 then transmits another command, TC2, which instructs
the external charger 252 to produce a charging field for charging
the IPG 100, in case it is not providing one already. TC2 can be
formatted similar to TC1 as just described. The external charger
252 receives command TC2 during listening window LW 407b, and
replies with transmission RP 307. LW 407b can be longer than other
listening windows as the external charger 252 is on notice that it
will be receiving a possibly longer command TC2. RP 307 notifies
the external controller 254 of the receipt of the command, and may
again also include some status information.
[0044] As noted earlier, the external charger 252 can operate in
fast data transmit mode or in slow data transmit mode, which mode
of operation, in one example, can be determined based on the level
of alignment between the external charger 252 and the IPG 100. In
the example provided in FIG. 9B, the external charger 252 begins
operation in the fast data transfer mode as a default once it has
handshaken with the external controller 254 in the manner just
described. This is preferred even if the external charger 252 is
already well aligned with the IPG 100, i.e., if alignment circuitry
103 already indicates sufficient alignment, which it very well may
be if it were already providing a charging field to the IPG 100
(FIG. 9A). If alignment is already sufficient, or if alignment is
achieved quickly, then the system will not remain the fast data
transfer mode for long, as will be described below.
[0045] In fast data transmit mode, the external charger 252
alternates between periods CF' 402 and SX 403, each with relatively
equal duration. During periods CF' 402, the external charger 252
charges the IPG 100 by producing a magnetic charging field at coil
88, and in state SX 403 it transmits charging information, such as
alignment information provided from alignment circuitry 103 and
possibly other charging parameters already mentioned, to the
external controller 254. The external controller 254 receives this
information during periodic receives periods RX' 305, which
correspond with the SX transfers from the external charger 252. The
external controller 254 can infer from the received alignment
information whether the external charger 252 is operating in a fast
data transit mode, and accordingly can schedule the receive period
RX' 305 at appropriate times so that data transfer during states SX
is synchronized. Alternatively, the SX transmission can
specifically include an indication of the external charger 252's
data transfer mode.
[0046] Once the charging information is received at the external
controller 254, it can be processed if necessary and forwarded to
the display 82 device for user review. By alternating relatively
rapidly between CF and SX, the external charger 252 provides
near-real-time alignment information to the user, which allows the
user to take quick responsive action to try and better position the
external charger 252 relative to the IPG 100. Although during the
fast data transit mode charging of the IPG battery 26 would be
twice as slow, this mode should not last for long, and the battery
26 is still being charged to some degree.
[0047] Eventually, the user will be able to align the external
controller 254 with the IPG 100, which is indicated in FIG. 9B at
time 312. At this point, the fast data transit mode between the
external charger 252 and external controller 254 could cease, and a
slow data transmit mode entered. However, in the illustrated
example, these devices continue to operate in fast data transmit
mode during period 405 to account for any additional movement by
the user to fine tune the alignment, which can be on the order of
seconds. During period 405, alignment circuitry 103 can continue to
be checked by the external charger 252 to ensure that good
alignment continues to be established, and that the fast data
transfer mode can eventually be left. After period 405, the
external charger 252 enters the slow data transit mode, and the
external controller 254 stops listening for SX, and thus receive
periods RX' 305 are no longer present. Again, the external
controller 254 will know based on the received alignment
information when the external charger 252 has left the fast data
transfer mode and when period 405 has ceased.
[0048] After period 405, the external charger 252 enters the slow
data transit mode as just noted, which is illustrated in FIG. 9C.
In slow data transmit mode, the external charger 252 continues
charging the IPG 100 during periods CF 401, but continues
periodically listening for any telemetry from the external
controller 254 during listening windows LW 407. The external
charger 252 also requests relevant charging information from the
IPG 100, such as its battery level and temperature. Eventually, the
external charger 252 will package the IPG's charging information
with the external charger's charging information to the external
controller 254.
[0049] Procuring IPG charging information occurs by external
charger 252 transmitting a command TI1 to the IPG 100 along link
266 (FIG. 7). The duration of TI1 is typically long enough to
coincide with one of the IPG's listening windows LW, such as LW
415a in the illustrated example, and is repeated to ensure that it
can be fully received during a listening window LW 415. The TI1
command can include in one example 19 bytes of alerting code, 3
bytes containing device ID of the IPG 100, 1 byte of command
requesting status information, and 2 bytes of error correcting code
(e.g., CRC)--similar to the commands sent from the external
controller 254 to the external charger 252 (FIG. 9B).
[0050] Upon receiving the TI1 command, the IPG 100 transmits a
reply RP 439, which includes the required IPG charging information.
Synchronization of this reply 439 and receipt 426 at the external
charger 252 can be ensure by having the IPG 100 extended listening
window until it no longer receives any data, i.e., when the end of
command TI1 is sensed. The external charger 252 can store the
charging information received from the IPG 100 in memory. The
external charger 252 can repeatedly query the IPG 100 to update the
stored charging information. It is preferred for simplicity that
data transfer between the external charger 252 and the IPG 100
occur in this manner illustrated, instead of implementing a
handshaking/acknowledgment/reply type scheme as used between the
external controller 254 and the external charger, although this
more-complicated scheme could also be used. After receiving the
charging information from the IPG 100, the external charger 252 can
return to charging the IPG 100 by continuing to intersperse
charging filed periods CF 401 and listening windows 407.
[0051] Eventually, the external controller 254 will request
charging information from the external charger 252, although
because the system 201 is now operating a slow data transmit mode,
this may occur more sporadically, e.g., even ten seconds or so. To
transfer the charging information, the external controller 254
sends command TC3 and TC4 to the external charger 252 coincident
with listening windows LW 407c and 407d. This handshake and data
exchange is similar to that described earlier with respect to
commands TC1 and TC2, and so such details are not repeated here. In
any event, the external charger's reply 432 provides the charging
information--both the external charging information and the IPG
charging information--to the external controller during RX 421.
Again, this transmission occurs more slowly, but sufficiently
quickly to update the display 82 in the external controller with
the relevant charging information. After this, the external charger
252 can continue charging (401) and listening (407) as before.
[0052] If at any time during the slow data transmit mode the
external charger 252 becomes misaligned with the IPG 100, such
would be reported by the alignment circuitry 103 in the external
charger 252, and would eventually be reported to the external
controller 254. As such, the external controller 254 can once again
instigate the fast transmission mode via commands TC1 and TC2 as
described earlier with respect to FIG. 9B.
[0053] FIG. 9D shows control of the external charger 252 when the
external controller 254 needs to communicate data with the IPG 100,
as is its legacy function. This could occur for example if the
patient is trying to change the therapy being provided by the IPG
100. In this circumstance, the external controller 254 may not
necessarily know if the patient is currently operating his external
charger 252 to charge the IPG's battery. As mentioned earlier, the
charging field produced by the external charger 252 may interfere
with FSK communications between the external controller 254 and the
IPG 100. As such, having the charging field activated during
communications between the external controller 254 and the IPG 100
is unadvisable. One way of getting around this problem would be to
alert the user to manually shut off the external charger 252 before
beginning communications between the external controller 254 and
the IPG 100. But this puts additional operational burden on the
user.
[0054] FIG. 9D illustrates a solution in which prior to
communications with the IPG 100, the external controller 254 will
instruct the external charger 252 to shut off, and then to turn
back on if necessary, i.e., if the charger was operating in the
first place. Because the external controller 254 automatically
shuts off operations of external charger 252, it is no longer
necessary for the user to manually discontinue charging before
beginning communications between the external controller 254 and
the IPG 100. This makes operation by the user much simpler while at
the same time ensuring that there is no interference. In a
preferred embodiment, the external controller 254 always sends at
least one command to suspend the external charger 252 before
communicating with the IPG 100, even if it is unnecessary because
the charger 252 is not currently engaged.
[0055] In FIG. 9D, the external controller 254 suspends operation
of the external charger 252 during period 500; communicates with
the IPG 100 during period 501; and recommences charging (if
necessary) in period 502. In period 500, the external charger sends
commands TC5 and TC6 to the external charger to suspend charging,
which occurs in the same manner as commands TC1 and TC2 describes
previously (FIG. 9B). The external charger 252 can confirm that it
has suspended charging in reply 331. If the external charger 252 is
not currently engaged in charging, it may additionally inform the
external controller 254 of that fact in reply 331. If the external
charger 252 is not present at all, e.g., if it is distant from the
patient and out of communication reach, then no acknowledgment AK
327 is received at the external controller 254, which can then
simply begin communications with the IPG 100 during period 501.
[0056] While period 500 in FIG. 9D only shows the external
controller 254 shutting down the charging field 401, it is
understood that similar instructions TC5 and TC6 can be used to
shut down any operation that the external charger 252 is carrying
out with the IPG 100. For example, if the external charger 252 were
in the process of requesting charging information from the IPG 100
(as shown by command TI1 in FIG. 9C), the external controller 254
will automatically shut off any FSK communication between the
external charger 252 and the IPG 100 during the time that the
external controller 254 wants to communicate with the IPG 100.
[0057] In period 501, the external controller 254 communicates with
the IPG 100, using commands TI2 and TI3, and the type of
handshaking procedure already discussed. Alternatively,
communications between the external controller 254 and IPG 100 can
take place in any manner as they occur in legacy systems.
Typically, commands sent from the external controller to the IPG
100 represent some information that the external controller 254
wants to send to the IPG 100. Such information can relate to status
inquiries, wake up messages, power down messages, turning
stimulation on/off, level or amplitude of stimulation pulses,
duration or frequency of stimulation pulses, selection of
electrodes to be activated, etc. The external controller 254 will
compile this information into appropriate commands (such as TI2 and
TI3) that can be understood by the IPG 100. Of course, the exact
format of the commands will correspond to the type of IPG 100.
Communication between the external controller 254 and the IPG 100
can also include information transmitted from the IPG 100 to the
external controller 254. Two examples of such communication are
shown by way of messages AK and RP in period 501.
[0058] Once these communications are complete, the external
controller 254 can once again instruct the external charger 252 to
commence charging during period 502. Once again, this can occur
using commands TC7 and TC8 and the handshaking procedure already
discussed. However, it is not strictly necessary to issue commands
TC7 and TC8 to recommence charging. For example, if the external
charger 252 was not producing a charging field, which would be
evident based on a lack of an acknowledgment 327 or an indication
of no charging in the reply 331, the external controller 254 may
dispense with sending commands to recommence charging during period
502. In fact, this may be preferred to prevent unwanted engagement
of the external charger 252. Alternatively, it may be harmless to
send the commands TC7 and TC8 to recommence charging in any event:
if the external charger 252 is out of range, such commands will
once again simply not be acknowledged (352); if the external
charger 252 was not previously engaged in charging--for example, if
the charger had not been turned on by the user--it can choose to
simply ignore the commands. If the external charger 252 was engaged
in charging, it can confirm recommencement of charging to the
external controller 254 in reply 356, and can continue providing
charging information to the external controller 254 in the manners
previously described.
[0059] Although not shown in FIG. 9D for simplicity, it should be
understood that commands TC7 and TC8 may instruct the external
charger 252 to enter the default fast data transmit mode. This
might be beneficial to ward again the possibility that the external
charger 252 became misaligned while it was suspended during period
501, a problem better handled during the fast mode as described
earlier.
[0060] Although discussed in the context of providing charging
information to the external controller 254, it should be recognized
that the communicative flexibility provided by modifications to the
external charger 252, and the FSK links 251 and 266 it supports,
can be put to other beneficial uses in the system 201. This
disclosure should therefore not be limited in its applicability to
that context.
[0061] Although particular embodiments of the present invention
have been shown and described, it should be understood that the
above discussion is not intended to limit the present invention to
these embodiments. It will be obvious to those skilled in the art
that various changes and modifications may be made without
departing from the spirit and scope of the present invention. Thus,
the present invention is intended to cover alternatives,
modifications, and equivalents that may fall within the spirit and
scope of the present invention as defined by the claims.
* * * * *