Post on 05-May-2022
Public Information
Ultra-Low-Power Circuits for Wearables
Philippe Bourban
30.11.2016
Public Information 2 11/30/2016
Outline
• ON Semiconductor quick facts
• Power budget of some wearable devices
• Things to think about to make ULP circuits
• A few circuit examples
3 Public Information
• Headquarters: Phoenix, AZ
• Employees: ~30,000 globally
• Revenue: ~$5Bn(1)
• Market Capitalization: ~$4.9Bn(2)
• Ticker: ON
• Founded: Spun-off from Motorola 1999, IPO 2000
(1) Estimated Fiscal 2017 Revenue per Factset 11/8/2016; (2) As of October 24, 2016; Sector % based on 3Q16
ON Semiconductor Today
4 Public Information
Proven Leadership Growth Drivers
Industrial ASIC #1
Notebook Adapters (ACDC) #1
Adaptive Front Lighting #1
Automotive Image Sensors #1
Linear VREG #1
Security Image Sensors #1
Audiology DSP Systems #1
PC Core Power (DCDC) #1
White Goods IPM #2
Protection #1
GP Op Amps #2
Automotive
Sources: iSuppli, IMS Research, Strategy Analytics, Fuji Chimera Research, ON Semiconductor Business Units and Corporate Marketing
Power Conversion & Motor Control
Image Sensors
Industrial IoT Wireless Devices
Public Information 5 11/30/2016
Typical elements in wearable devices
Sensor(s)
Data
acquisition
chain(s)
Data
processing
Wireless
connectivity
• Signal conditioning
(amplify, filter…)
• A/D conversion
• μC
• DSP
• ASIP
• Dedicated HW
• NFC
• RFID
• Bluetooth Classic
• Bluetooth Low-Energy
• ANT
• Wifi
Power management unit
Driver Actuator /
Display
• Accelerometer
• Gyroscope
• Magnetometer
• Altimeter
• Barometric pressure
• Heart rate
• ECG
• Oximetry
• Respiration
• Infrared
• Skin conductance
• Skin temperature
• Ambient temperature
• Ambient light
• UV
Public Information 6 11/30/2016
Power budget of some wearables (1) AR glasses Sportswatch Fitness tracker Fitness tracker
Recon Instruments Snow2 HUD Samsung Gear S2 Tomtom Spark Cardio+Music Garmin Vivosmart HR+
1200 mAh @ 3.7V 250 mAh @ 3.8V 230 mAh @ 3.8V 80 mAh @ 3.8V
6 hours 36 hours (display on)
72 hours (display off)
5 /11 hours (music/GPS)
3 weeks (activity tracking)
8 hours (use)
120 hours (standby)
740 mW 26 mW (display on)
13 mW (display off)
175/80 mW (music/GPS)
1.7 mW (activity tracking)
38 mW (use)
2.5 mW (standby)
• Wifi, BT, GPS
• 9-axis accel. & gyroscope
• Compass sensor
• Pressure sensor
• Temperature sensor
• 0.2” TFT-AMLCD display
• Wifi, BLE, NFC
• 6-axis accel. & gyroscope
• Heart Rate sensor
• Pressure sensor
• Ambient light sensor
• 1.2” Super Amoled display
• GPS, BT
• 6-axis accel & gyroscope
• Heart Rate monitor
• Bio-sensor
• 3-axis magnetometer
• 1.3” LCD display
• GPS, BLE, ANT
• 3-axis accelerometer
• Heart Rate sensor
• Pressure sensor
• 1.6” TFT-LCD display
• 1 GHz dual-core OMAP4430
• Graphics processor
• 1 GHz dual-core Exynos
3250
• ARM Cortex M7
• Atmel 8-bit MCU
• 120 MHz ARM Cortex M4
Data from www.techinsights.com
Public Information 7 11/30/2016
Power budget of some wearables (2) Bluetooth earbuds Bluetooth earbuds Bluetooth earbuds Hearing Aid
Bragi Dash Earin
Motorola moto hint 89765N
100 mAh @ 3.7V 60 mAh @ 3.7V 120 mA @ 3.7V 160 mAh @ 1.2V
(disposable)
4 hours 3 hours 10 hours 100 hours
92 mW 74 mW 44 mW 2 mW
• BT audio streaming
• 3-axis accelerometer
• Gyropscope
• Magnetometer
• Dual pulse oxymeter
sensor
• BT audio streaming • BT audio streaming • Audio processing
• Audio streaming
Public Information 8 11/30/2016
A few power consumption numbers
Circuit Power consumption
BLE radio 10 mW (peak)
GPS 70 mW
Wifi 240 mW
ARM Cortex M3 0.1 mW/MHz
Exynos 7420 0.25 mW/MHz (14nm FinFET)
12-bit ADC @ 1 Msps 0.2 mW
3-axis digital accelerometer 3 mW (peak)
1 to 30 uW (average @ 1 Hz)
Public Information 9 11/30/2016
System
Software / algorithm
Architecture
Circuit
How to make ULP circuits?
Technology
• Main power contributors?
• HW/SW partitioning
• Power-down
• Complexity
• Concurrency
• Regularity
• Processor architecture
• Analog vs digital
• Parallelism/Pipelining/Encoding
Digital:
• Voltage reduction
• Activity reduction
• Power gating
• State retention
• Flavors (LP, etc…)
• Multi-threshold devices
• FDSOI / DDC / back-biasing
Analog:
• Weak inversion
• Transistor sizing
High
Low
Typ
ica
l P
ow
er
Sa
vin
g
Public Information 10 11/30/2016
Analog
Digital
Radio
Audio streaming
Analog
Digital
Radio
Consumer monitoring
Analog
Digital
Radio
Medical implantable
Understand the power breakdown
• Sleep 96% of the time
• Wake up every 100 ms
to send 20 bytes
• Dynamic power is
dominant
• Avg power: 50 mW
• Sleep 99.9% of the time
• Wake up every 10 s to
send 20 bytes
• Memory leakage power
is dominant
• Avg power: 1.5 mW
• Radio active 7.6% of the
time
• Receive data @ 48 kbps,
10 ms frames
• Dynamic power dominant
(audio decompression)
• Avg power: 1.5 mW
Public Information 11 11/30/2016
Select the right processor architecture
Dedicated
Hardware
DSP
ASIP
General
Purpose
Processor
Energy
Efficiency
Flexibility
Public Information 12 11/30/2016
• Pdyn = a* f * C * Vdd^2
• Pstat = Ioff * Vdd
Reduce the supply voltage: yes but…
• Trade-off power versus performance (operating frequency)
• Process variability at low voltage Vt mismatch FD-SOI, DDC
Public Information 13 11/30/2016
Cost • Development
• Production
Which process technology?
Today’s popular choices for a wearable SoC Low-cost : 180 nm
Mainstream : 65 nm / 55 nm
Advanced : 40 nm / 28 nm
Performance • Analog (noise)
• Computing
Power • Static
• Dynamic
Flash
availability
Die area
Memory needs
RF technology System
partitioning
Technology
selection
Public Information 14 11/30/2016
ULP circuit examples
Public Information 15 11/30/2016
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
1.E-06 1.E-04 1.E-02 1.E+00 1.E+02
Effi
cie
ncy
[%
]
Load Current [mA]
Buck efficiency vs load (mA) @ Vout=1.2V
Vin=3.3V
Vin=1.8V
Efficient DC-DC converter
LTC3549 (high efficiency buck converter) ON Semiconductor
High efficiency step-down conversion at low load currents (100 nA to 100 mA) is important
for ULP circuits or for use cases where the system is often idle (e.g. vital signs sensing)
Buck efficiency vs load (mA) @ Vout = 1.5V
42% @ 100 mA load
85% @ 1 mA load
Public Information 16 11/30/2016
ADC energy efficiency
PCM4220 (TI)
MAX98091 (Maxim)
WM8786 (Wolfson)
AD1974 (AD)
ISL26102 (Intersil)
LTC2440 (Linear)
TLV320 (TI)
State-of-the-art in 2013
Public Information 17 11/30/2016
ADC energy efficiency
ON – 2007
(audio)
ON – 2010
(ECG)
ON – 2014
(audio)
ON – 2002
(monitoring)
PCM4220 (TI)
MAX98091 (Maxim)
WM8786 (Wolfson)
AD1974 (AD)
ISL26102 (Intersil)
LTC2440 (Linear)
TLV320 (TI)
State-of-the-art in 2013
Public Information 18 11/30/2016
• More sensors
• More wireless, with multi-standard radios
• Lower power consumption of individual
functions
• Smaller technology nodes (40nm & 28 nm)
• SoC integration (AFE + mC + radio)
• Security
Trends in wearables
Public Information 19 11/30/2016
• ULP circuits are at the heart of wearables
• Low-power is in the DNA of local companies
due to the watch industry heritage
• Neuchâtel and Western Switzerland are well
equipped to solve most low-power
challenges in wearables devices
Conclusion
Public Information 20 11/30/2016
Questions?