1
Sensor Hub
for Smartphones & Tablets
Vijendra Kuroodi
vkuroodi@rohmsemiconductor.com
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Agenda
2
• Sensor Hub for Mobile Handsets
• Market drivers
• Importance of Activity Detection
• Case study & expected evolution
• Sensor Hub for Tablets
• Market drivers
• Gaming & Sensor Fusion
• Expected evolution
• Key features to look for in sensors
• Integration of Sensors
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Customers Seek Product Differentiation
3
Phone manufacturers need something unique
– Features that stand out
– Features that are not power hungry
– If features lead to new services, that would be even better
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Importance of Activity Detection
Phones
Activity Detection
Data Analytics
& Services
4
Revenue Streams
Cloud based
services
(push or pull)
GPS
Activity detection for driving safety : Disabling some features while driving
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Activity Detection Requires Low Power Expertise
5
• Low power devices have been available
• Some claim 10 Years on a single battery!
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Sensor Hub for Smartphones
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Two Ways of Using Sensor Hub Microcontroller
• Inside the phone
– Reference design for some customers
• Outside the phone
– As a Phone Accessory (eg: sports band)
• Bluetooth LE interface
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7
Sensor Hub Low Power Microcontroller
Phones using Sensor Hub can significantly reduce power
consumption when application continuously requires sensors
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8
Case Study: Sensor Hub Microcontroller
9
ML610Q792 is a highly optimized Sensor Hub Microcontroller for
Phones & Smartphones
Dual I2C interface
WCSP48
Host I/F
Accelerometer
Gyroscope
Geomagnetic sensor
Pressure sensor
Ambient light sensor
Proximity sensor
UV sensor
Temperature sensor
Humidity sensor
Etc.
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CPU
U8 (8bit RISC CPU Core)
Power Supply
I/F : 1.65V - 3.6V
Analog/Digital : 2.5V - 3.6V
Operating
Frequency
4MHz
Flash ROM
64kB
CPU RAM
4kB
Logging RAM
8kB
Accelerator
16bit Multiply & Division /
Multiply & Accumulation /
Square Root
Host I/F
SPI (2MHz) / I2C
Sensor I/F
I2C x 1, SPI x 1
IDD
4MHz
900uA
Halt
0.6uA
Package
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0.4mm pitch WCSP
3.1mm x 3.0mm
Case Study: Power Consumption
10
Power consumption of a smartphone using ML610Q792 was 20x lower than a
regular phone running the pedometer/calorie calculation algorithm
Conditions
Power Consumption
•Smartphone CPU: Hummingbird processor Cortex A8
@1GHz
•Setting : Airplane mode: ON
Wi-Fi: OFF
Bluetooth: OFF
Display: OFF
•Conditions : Lapis Semiconductor’s pedometer / calorie
calculation program & algorithm running on main CPU
ML610Q792
+
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•Smartphone CPU: Hummingbird processor Cortex A8
@1GHz
•Setting : Airplane mode: ON
Wi-Fi: OFF
Bluetooth: OFF
Display: OFF
•Conditions : Lapis Semiconductor’s pedometer /
calorie calculation program & algorithm running on
ML610Q792
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41.0mA
1.6mA
Sensor Hub Software Development Kit (SDK)
2) Sample application program
11
: Source code
: Library
HOST I/F application
Software
: Source code
Sensor oriented
application
(ex. Pedometer)
Logging
application
OS I/F
application
Firmware update
application
3) Read/Write sensor driver
Sensor control application
Accelerometer
driver
xxx sensor driver
Serial console
sample
yyy sensor driver
HOST I/F
driver
Sensor control
CPU I/F driver
Operating
System
specific driver
1) Sensor specific drivers
HOST CPU
Hardware
Sensor Hub Microcontroller
Sensors
Accelerometer
Magnetometer
Gyroscope
Ambient light
sensor
Pressure
sensor
Temperature /
Humidity
UV sensor
Proximity
sensor
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Three main components
in SDK
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Sensor Fusion Scenarios
• Examples of applications requiring Sensor Fusion
– Inclinometer: Steering wheel input for game
– Device orientation
• Augmented reality control
• First person style games
• Pointing applications (Remote Control)
• Requires about 20 MIPS on a 32 bit processor
• Applications Processor is awake
• Sensor Fusion requires performance while Activity
Detection requires low power
– Using a 32 bit Sensor Hub to do both would be sub-optimal
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Sensor Hub for Phones & Tablets
Phones
• Low power sensor hub => Activity
Detection
• Sensor Fusion on Apps Processor
Tablets
• Performance sensor hub => Gaming
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13
Benefits of Using an External Sensor Hub
• Time to market
– Software is provided
• Avoids work on low level driver software on multicore processors
• Power savings = Longer battery life between charges
– Small CPU cores in multi core chips are likely to consume more
power than the low power Sensor Hub
• Product differentiation
– New revenue streams open with the ability to provide activity
detection
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14
Sensor Hub & Sensor Fusion for Tablets
SENSOR HUB
• 32 bit MCU HW Solution primarily for tablets & gaming
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Evolution of Sensor Hub for Tablets
• Tablets have larger power budgets than mobile
handsets
– Gaming is the driver & performance is key
– We will see both Hardware (16 / 32 bit MCUs) and
software implementations of Sensor Fusion
• 16 / 32 bit MCUs will likely be absorbed by main
chipset
• Sensor Fusion IP will be available from several
suppliers
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16
Sensor Solutions for Phones & Tablets
Ambient Light
Proximity
Hall Effect
Temperature
MEMS
Accelerometers
& Gyroscopes
Touch Sensors
IR/ Image / PIR
UV –A/B
Sensors
Sensor Hub
Sensor Fusion
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OIS
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17
Choosing an Ambient Light Sensor
Block diagram
VCC
18
Specification Outline
DVI
BH1730FVC
ADC
AMP
PD
AMP
ADC
PD
VCC [V]
ADC Logic
+
I2C Interface
+
INT Interface
POR
OSC
GND
INT
Package Outline
IDD(Operating) [uA]
-/150/200
SDA
IDD(Power Down) [uA]
-/0.85/1.5
I2C ADDR
0101001
I2C Speed
F/S
integration time [ms]
2.7 step to 688
×1,×2,×64,×128
GAIN mode
Measurement resolution
Digital 16bit
0.008 lx step( x128 mode typ.)
0.0011 lx step max.
Package size [mm]
3.0mm
(typ.)
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SCL
Output format
1.6mm(typ.)
0.75mm
(max.)
2.4～3.0～3.6
Operating Temp. [℃]
-40～70
Storage Temp. [℃]
-40～100
Unit:mm
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3.0×1.6×0.75
(WSOF6)
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Ambient Light Sensor Features
19
• Low light sensitivity, dynamic range / adjustable gain
• Measurement of visible light and infrared light eliminates source
dependency ( ex. Incandescent Lamp. Fluorescent Lamp. Halogen Lamp.
White LED, Sun Light )
• I2C Digital output
• Interrupt output with high and low thresholds
• Power down function
• 50Hz / 60Hz noise rejection
• Micro-power operation; 1.8V logic interface
• True Lux calculations with varying optical window characteristics
• Device driver & documentation
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Handling Spectral Sensitivity Variations
Fluorescent Lamp
20
Incandescent Lamp
Each optical source
Has a different
spectrum
Spectral
distribution
Spectral
distribution
The maxima of energy is
displayed as 100%.
Wavelength(nm)
Strong in visible spectral range.
Weak in the infrared range
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Spectral Power (%)
Spectral Power (%)
Sensor outputs
different values even if
brightness appears to be
the same to
human eyes.
Silica Bulb
The maxima of energy is
displayed as 100%.
Wavelength(nm)
The energy of the infrared region is
larger than that of the visible light.
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Sensitivity Ratio for Various Light Sources
Low cost ALS
Good Ambient Light Sensors
Incandescent / Fluorescent Sensitivity Ratio
Rohm Incandescent / Fluorescent Sensitivity Ratio
Clear Bulb
Clear Bulb
Silica Bulb C
Silica Bulb C
Silica Bulb B
Silica Bulb B
Silica Bulb A
Silica Bulb A
Fluorescent Lamp(6700K)
Fluorescent Lamp(6700K)
Fluorescent Lamp(5000K)
Fluorescent Lamp(5000K)
Fluorescent Lamp(2800K)
Fluorescent Lamp(2800K)
Light
Source
Types
0.0
1.0
2.0
3.0
4.0
Output Current Ratio
True Lux readings
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5.0
Light
Source
Types
0.0
1.0
2.0
3.0
4.0
Output Current Ratio
Low cost sensors output different
values for different light sources
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5.0
Optical Window and Glass Related Calculations
Optical window
guide line
( from Rohm )
Product mechanical
data near ALS
(from customer)
Optical simulation
results
Optical window
simulation
If it needs to improve.
Optical
window
Case
Ambient Light Sensor
Optical Window
design guide line
PDA　YZ平面方向
1
0.9
0.8
0.7
相対受光量
ALS IC
0.6
0.5
0.4
0.3
0.2
0.1
0
Optical
simulation
results
-90
-60
-30
0
角度（°）
30
60
90
Optical window simulation and identification of coefficients for a given glass type
are very important for reliable ambient light measurements
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22
Sensor Response Matched to Optical Window
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New Ambient Light + UV Sensor Concept
• True Lux measurements taken to the next level
• UV sensing could be added to phones
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24
Selecting a Proximity + Ambient Light Sensor
• Dual photo diodes for Ambient Light Sensor – Better tunability
• Linear to Log converter block simplifies ADC requirements
• Choose good low light response over dynamic range
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The Logarithm Converter
26
Standard Offerings
Output of competitor’s proximity.sensor
Output of BH1772GLC
180
160
140
120
100
80
60
40
20
0
1
0.9
The output value is
almost in inverse
proportion to the distance.
0.8
(measurement conditions)
Reflecting object: Kodak18% Gray card
ILED=200mA(IrLED:SIM-030)
The output value changes greatly
0.7
出力電圧[V]
Sensor Output [count]
Proximity Sensor output is linearized
0.6
0.5
0.4
The output value changes
very little
0.3
0.2
0.1
0
20
40
60
distance [mm]
80
100
0
0
20
40
60
80
100
distance[mm]
• Identify resolution requirements
• Look for Log to Linear converter
• Look for simulation services (reflections, optical windows, ALS / Proximity
cross talk)
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Hall Effect IC Applications
Hall IC for magnetic switch
27
Bipolar latch Hall IC
899EA
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Expertise, Support and Ecosystem
Sensors Expertise
Analog & Mixed Signal, Microcontrollers, MEMS, Optical Systems
Support
• Technical and Applications
support
• Modeling
• Simulation
• Local or Regional support
• Special Request fulfillment
• Integration Services
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Ecosystem
•
•
•
•
•
•
Software solutions
Driver availability
Fusion implementations
3rd party support
Reference designs
Supported Hardware and
Software
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Summary
29
• Sensor Hub for Mobile Handsets & Tablets have
different requirements
– Sensor Hub for Mobile Handsets
• Low power Activity Detection enables driver safety features
and ability to add new cloud based services
– Sensor Hub for Tablets
• High performance gaming is the driver. Sensor Hub MCU with
Sensor Fusion or SW based sensor fusion are key
• Work with Sensors specialists
– Take advantage of lessons learned and integration/
consultation services
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