Anantha P. Chandrakasan Joseph F. and Nancy P. Keithley Professor of Electrical Engineering, Department Head, MIT Electrical Engineering and Computer Science

1. Energy-Efficient System Design
for Wearable Platforms
Anantha Chandrakasan
Department Head, EECS
Acknowledgements: Ishwarya Ananthabhotla, Laura
Giarré, Nathan Ickes, Dongsuk Jeon, Priyanka
Raina, Daniela Rus, Nick Wang

2. 2
Wearable Systems
Finger-mounted reading device
for the blind [P. Maes, Media Lab]
Body Worn Health Monitoring
[IMEC and Partners]
Navigation Device
[D. Rus, CSAIL]
Virtual Touch Screen
[D. Katabi, CSAIL]

3. 3
Battery
Processor (Bottom) Sensors (Bottom)
Processor Board
Sensor Board
Accelerometers
ADC
Processor (Top)
CPU/Radio
Solar Cell
Antenna
Low-Power Sensor System

4. 4
Power Button
ToF Camera
Navigation Device Concept
Obstacle
Ground Plane
Interface
Processor
Wireless
Battery
(inside)

5. 5
Use of Hardware Accelerator
Low-light Enhancement
LLE outputFlash
No-Flash
• More than 100x reduction in energy consumption using an
accelerator for computational photography
• Parallel architectures allows low-voltage operation
[R. Rithe, ISSCC 2013]

6. 6
Combine Processor (CPU) with
Accelerators
 Overall energy reduction >10x in complete applications
compared to CPU-only approach (for EEG and ECG
applications)
64kb
SRAM 1
µC CORE
FFT
MEDIANGPIO FIR
MISC
64kb
SRAM 2
MU
LT
JT
AG
COR
DIC
TIM
ER
SER
IAL
3mm
4mm
RTC
Joyce Kwong
[ESSCIRC ’10]

7. 7
System-Level Energy Savings
Accelerometer
Power
Management
Processor
Acceleration
Data
Status
Decision
Standing/Sitting
Walking
Low Power Mode
(Slow Frame Rate)
High Speed Mode
(Fast Frame Rate)

8. 8
Energy Harvesting Techniques
Piezoelectric
Micro-Power
Generator
Sang-Gook Kim (MIT)
Thermal
Harvesting
Wearable Systems Can be Powered from Energy
Harvesting
Chris Van Hoof (IMEC)
Wireless
Power
Nachiket Desai (MIT)

9. 9
Endoelectronics chip:
EP harvester architecture
*
VIN
VEP
The endocochlear potential (EP) was
discovered 60 years ago by Georg von Békésy
Mercier, P. P., A. C. Lysaght, S. Bandyopadhyay, A. P. Chandrakasan, K. M. Stankovic, "Energy
extraction from the biologic battery in the inner ear," Nature Biotechnology, Nov. 2012.
Maximum
Extractable
Power:
1.1 to 6.25nW

10. 10
Fully-Implantable Cochlear Implant
Conventional CI
External microphone,
processor, coil
Fully-Implantable Solution
• Charge in 2 minutes for typical day use
Yip, M., R. Jin, H. H. Nakajima, K. M. Stankovic, A. P. Chandrakasan, "A Fully-Implantable Cochlear Implant SoC
with Piezoelectric Middle-Ear Sensor and Energy-Efficient Stimulation in 0.18µm HVCMOS," ISSCC 2014.

11. 11
Principles and Practice of Assistive
Technology (PPAT) and AT Hack @ MIT
Blicycle (PPAT 2011) : Steven Levine and Emily Obert
Touch and Sign (PPAT 2014): Jeffrey Drucker, Yi Tong, David Ke, Jodie Chen
Accessible Oven design (PPAT 2013): Abigail Klein, Jose Marcon, Jakub Sanak
AT Hack: Ishwarya Ananthabhotla, Jaya Narain, Jennifer Tylock
Courtesy Ishwarya Ananthabhotla

12. 12
We acknowledge the generous support of the following
organizations :
Energy efficient design is critical in enabling
practical wearable devices for the visually-
impaired. A system-level design approach is
needed to reduce energy.
Summary