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Energy Harvesting

Reference Design

Embargo Until May 25, 2011

Sustainable, Ultra-Low-Power Solution for Wireless

Sensor Node Applications

2

Dramatic Growth Ahead in Energy Harvesting

Energy harvesting device market is projected to grow

exponentially this decade

10B+ energy harvesting devices forecast to ship by 2019 – a 20x

increase over ~500 million units that shipped in 2009

(Source: IDTechEx)

No need for conventional batteries in many designs

Batteries are not “green” – must be recycled, often

end up in landfills

Costly and inconvenient to replace

Unreliable under certain operating conditions

Energy harvesting technology is environmentally friendly

Natural energy resources are inexhaustible

Conventional energy generation produces greenhouse gases

We’ve reached a tipping point in energy harvesting and low-

power wireless technologies

Energy harvesters have become cost-effective and efficient

Ultra-low power wireless MCUs can now operate at power levels low

enough to implement wireless sensor nodes using harvested energy

3

Silicon Labs’ Energy Harvesting Wireless Solution

Solar-powered design

Measures temperature,

light level and charge

level

Single-chip Si1012

wireless MCU

Transmits data to

wireless USB adapter

Connects wireless sensor

node to PC

MCU runs HID USB

software as well as

EZMac wireless network

stack

Optimized RF & USB

implementation

Displays data from

wireless sensor node

No special software

drivers required

Wireless sensor node Wireless USB adapter Wireless sensor network GUI

Comprehensive Energy Harvesting Reference Design

4

Turnkey Wireless Sensor Node Design

Complete energy harvesting

wireless sensor solution

Includes all wireless network and

USB software

All circuit design including RF

layout available

Optimized for ultra-low

power consumption

Uses Silicon Labs single-chip Si10xx

wireless MCU for control and

connectivity

• Most power-efficient wireless MCU

available

• 20 nA in deep-sleep mode and 2

microsecond wake-up time

Reduces average system current

through smart power cycling

5

Based on Industry’s Lowest Power Wireless MCU

Si10xx family extends battery life

Lowest active current saves energy when

device is running

Lowest sleep current saves energy when

device is inactive

Industry’s leading RF performance

Up to +20 dBm output power without the need for external PA

-121 dBm receive sensitivity – greatly increases range

Integrated dc-dc switching regulator extends input voltage

range

0.9V to 3.6V operation

6

Sleep

Button

Press

?

RTC on

Wake-up every 1s

Transmit light

level

Send temp &

charge level every

60s

RTC on

for 3

minutes

?

Yes

No

NoYes

In Sleep mode, ENERGY-HARVEST-RD

consumes ~ 3uA

(leakage from battery management chips)

In RTC mode, ENERGY-HARVEST-RD

consumes ~ 3.8uA

(MCU RTC adds 800nA to existing leakage)

In Active mode, ENERGY-HARVEST-RD

consumes ~ 51uA average current

(3uA of this is battery management leakage)

Operating Modes and Power Consumption

LP sleep mode of the wireless

MCU consumes 65 nA and uses

the pin port match to wake up

(2 µs)

The wireless MCU in RTC sleep

and the RF transciever in

standby is 350 nA + 450 nA,

respectively

Voltage regulator and

associated circuitry consumes

3 µA of leakage current

Active mode turns on the MCU

and the RF transceiver

29 mA for transmit current at +13

dBm

19 mA receive current at -121 dBm

sensitivity

7

Charging Times for Thin Film Battery

Time to fully charge an empty battery with no system load

Electric

Light50 – 200 Lux

Direct

Sunlight100K Lux

Office

Window≈ 1000 Lux

USB

ChargingLimited to 3 mA

24 hours 6 hours 2 hrs 30 minutes

8

Alternative Harvested Energy Sources

Solar

cell

Battery

Management

circuit

Thin film

battery

Auxiliary

Input

ENERGY-HARVEST-RD

RF Energy

Vibration

Thermal

The reference design can be powered by different sources of

harvested energy

RF, vibration (piezoelectric) and thermal sources

9

Minimal Bill of Materials = Low System Cost

Wireless Sensor Board Wireless USB Adapter

Front

Back

Solar

Cell

Si1012

Wireless

MCU

Debug

connector

Printed

Antenna

Thin

Film

Battery

Si4431

RF IC Running

EZMac Software

C8051F342

USB MCU

Running HID

Firmware

10

Emerging Energy Harvesting Applications

Wireless sensor nodes

Home and building automation

Industrial control systems

Medical monitoring systems

Infrastructure sensing systems

Security systems

Agricultural monitoring systems

Asset tracking systems

11

Summary

Market interest in energy

harvesting solutions is large

and growing

Silicon Labs’ turnkey energy

harvesting reference design

for wireless sensor nodes

speeds time to market

Wireless networking and USB

software included in design

Low bill of materials (BOM)

Complete circuit design with RF

layout

Schematics and Gerber files

Silicon Labs offers the lowest

power wireless sensor node

solution powered by

harvested energy

www.silabs.com

www.silabs.com/energy-harvesting