1. The document discusses the design of integrated circuits for miniature implantable medical devices (MIMDs) that are less than 4cc in size. 2. MIMDs can be implanted at the point of therapy using minimally invasive procedures due to enabling technologies like MEMS, chip-scale packaging, and solid state batteries. 3. Custom IC design takes advantage of opportunities in MIMDs like low/small temperature ranges, low frequency requirements, and moderate precision needs to minimize size and power consumption. Design techniques include complex power management and ultra-low power circuit design.

1. 1
Turn‐Key Analog & Mixed Signal IC Development & Support
60 N. McClintock Drive, Suite 1
Chandler, AZ 85226
1‐480‐497‐4511
http://www.cactussemiconductor.com
Integrated Circuit Design for
Miniature Implantable Medical
Devices
Andrew Kelly
Cactus Semiconductor Inc.
September 1, 2015

2. 2
Integrated Circuit Design for
Miniature Implantable Medical Devices
• Miniature Implantable Medical Devices
• Enabling Technologies
• Design Opportunities
• Design Techniques
• MIMD Example
• Conclusions

3. 3
Miniature Implantable Medical Devices
IMDs
~50 to 15cc
Chest/Abdomen
Long Leads/Catheters
Invasive Surgery
Pacemakers/Defibrillators
Spinal Cord Stimulators
Drug Infusion Pumps
MIMDs
< 4cc
Head/Neck/Limbs
Small Leads/Catheters
Minimally Invasive
ECG/EEG Monitors
Peripheral Nerve Stimulators
Micro Infusion Pumps

4. 4
Miniature Implantable Medical Devices
IMD Implanted in Chest
Leads Routed to Neck
Electrodes Attached to Nerve
Device Volume < 1cc
Small Enough to Implant
at Point of Therapy
• Example: Vagus Nerve Stimulator

5. 5
Enabling Technologies
1mm
• Micro‐Electro‐Mechanical Systems (MEMS)
• Microscopic Sensors, Actuators & Machines
• Manufactured with Integrated Circuit Equipment &
Processes
Medical Examples
Pressure Sensors – Blood Pressure
Accelerometers – Position, Activity
Chemical Sensors – Glucose, pH
Fluid Pumps – Drug Delivery

6. 6
Enabling Technologies
• Chip‐Scale Packaging (CSP)
MIMDs
28-pin MCU
250x Smaller than DIP

7. 7
Enabling Technologies
• Stacked Chip‐Scale Packaging (SCSP)
• Multiple Chips in One Package

8. 8
Enabling Technologies
• Solid State Batteries (SSB)
• Fabricated on Silicon Wafers
• Standard Semiconductor Processes & Equipment
• Functions like Standard Rechargeable Li‐Ion Battery

9. 9
Enabling Technologies
• Battery Capacity vs Volume
‐50
0
50
100
150
200
250
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Capacity (mA‐H)
Volume (cc)
Typical IMDs
MIMDs
Extremely Low Capacity
Extremely Low Volume
SSBs Lower Power Leads to
Device Miniaturization

10. 10
Enabling Technologies
• Application‐Specific ICs (ASICs)
• Eliminate Unnecessary Features & Functions
• Optimize Performance for Single Application
• Optimize Size/Power for MEMS Interfaces
• Optimize Inter‐Connect for SCSP
• Optimize Integration
• Optimize Total Power Consumption
• Enable Battery Volume Reduction
Customize Design to
Minimize Size & Power

11. 11
Design Opportunities
• Low/Small Temperature Range
125
135
145
155
165
175
185
195
205
215
‐60 ‐40 ‐20 0 20 40 60 80 100 120
MOS Drain Current (uA)
Temperature (oC)
Military
(-55 to +125)
Industrial
(-40 to +85)
Commercial
(0 to +70)
Post-Implant
(+35 to +40)
IMD
(+10 to +50)

12. 12
Design Opportunities
• Low Frequency Requirements
• EEG/ECG Bandwidth ~ 200Hz
• Blood Pressure Bandwidth < 100Hz
• Accelerometer Bandwidth < 1KHz
• Stimulation Therapy < 50KHz
• [4G Wireless > 2.5GHz]
Low Frequency
Enables Lower Power
Design

13. 13
Design Opportunities
• Moderate Precision Requirements
• Stimulator DAC Amplitude ~ 8‐bits
• ECG/EEG ADC Resolution ~ 12‐16 bits
• Pressure Sensor ADC Resolution ~ 10‐bits
• Accelerometer ADC Resolution ~ 8‐bits
• [Audio DAC ~ 24‐32 bits]

14. 14
Design Opportunities
• Moderate Precision Requirements
• Data Converter Figure Of Merit
• Common Metric to Measure Overall Performance
FOM )]
Low Precision Enables
Lower Power Design

15. 15
Design Opportunities
• Non‐Volatile Memory (NVM)
• Included in Most MCUs
• Holds Memory When Power is Removed
• MCU Can Be Disabled – Most of the Time
• Calibration for Analog Circuits
• Reduces Analog Performance Requirements
Reduced Performance
Enables Lower Power
Design

16. 16
Design Opportunities
• Battery Recharge
• Required for Most MIMDs
• Use Re‐Charge Session for Communication
• Use Communication to Calibrate Circuits
• Reduces Absolute Accuracy Requirements
• Reduces Accumulation of Timing Errors
Reduced Performance
Enables Lower Power
Design

17. 17
Design Techniques
• Wireless Communication
MICS
Medical Implant
Communication Service
2‐Way Communication
Radio Frequency ~ 400MHz
~ 500Kbps / ~ 2m
Additional RFIC
High Frequency Crystal
RF Antenna
40mW from Battery
Traditional Battery
NFMI
Near Field Magnetic
Induction
2‐Way Communication
Magnetic Induction < 1MHz
< 10Kbps / < 10cm
Integrated in ASIC
No Crystal
Shares Charging Antenna
No Battery Power
Solid State Batteries
Use NFMI for
MIMDs

18. 18
Design Techniques
• Complex Power Management
• Multiple Supply Domains
• Switched‐Mode Power Supplies
• Detailed Enable/Disable Control
• Digital Clock Gating
• Energy Harvesting
Example MIMD
• 4V Battery
• 10V Wireless Antenna
• Inductive Buck for Battery Charging
• Capacitive Buck for 2.5V Digital & LV
Analog
• Linear Regulator for 1.5V
Oscillator/Timekeeping
• Inductive/Capacitive Boost for 20V
MEMS Drive
Effective Power
Management
Minimizes System
Power Consumption

19. 19
Design Techniques
• Ultra‐Low Power Circuit Design
• Example: Ultra Low Power Bandgap Reference
Switched‐Cap
Architecture
Sample/Hold
Output
nA Supply
Current

20. 20
Design Techniques
• Smart Integration
• Assess All Available Components
• Consider Size, Power, Cost, Schedule, Risk
• Partition Design: Only Customize as Needed
• Not Maximum Integration
ASIC + MicroController
Not System‐On‐Chip

21. 21
Design Techniques
• Application Specific
Standard Products (ASSP)
• Basic Features Common to
Multiple MIMDs
• Significant Cost, Schedule,
Risk Reductions
• Fast‐Track to Proof of
Concept Device

22. 22
Design Techniques
• Custom IC Platform
Reduces Cost,
Schedule & Risk

23. 23
MIMD Example
• Neuro‐Stimulator
• 2 Electrodes
• Programmable
Stim Current
• Wireless
Communication
& Recharge
• Integrated Power
Management &
Timekeeping
• Implant at Point
of Therapy

24. 24
MIMD Example
• Neuro‐Stimulator
MCU in
WLCSP
SSB in
SCSP
ASIC in QFN
< 1cc Total
Volume

25. 25
Conclusions
• MIMDs are achievable by capitalizing on Enabling
Technologies and Design Opportunities
• Custom IC Design using unique Design Techniques
allows us to take full advantage of the opportunities
• ASSPs and Platform approaches reduce time, cost,
& risk

26. 26
Contact Information
Cactus Semiconductor Inc. is a fabless semiconductor
company. We offer full turn-key product design and production
as well as integrated circuit design services. Our expertise in
power management and analog circuits find value in products
for medical and portable applications.
Cactus Semiconductor Inc.
60 N. McClintock Drive, Suite #1, Chandler, AZ 85226
www.cactussemiconductor.com
Andrew Kelly
IC/Systems Architect
andy.kelly@cactussemi.com
480-497-4511 x203