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LINEAR LTC3108 User Guide

Summary

This technical guide explores the implementation of ultralow voltage energy harvesting for battery-free wireless sensor nodes. It details the use of the LTC3108 and LTC3109 power management ICs to convert minute levels of ambient energy from heat, light, and vibration into usable power. Ideal for engineers and system designers, the manual covers power management schemes and design features for industrial, automotive, and building automation applications.

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October 2010 Volume 20 Number 3

Ultralow Voltage Energy Harvester Uses Thermoelectric Generator for

4- and 6-supply monitors Battery-Free Wireless Sensors feature ±1.5% accuracy for

David Salerno

rails down to 1.2V 17

4mm × 7mm IC produces The proliferation of ultralow power wireless sensor nodes for

multiple power rails from a measurement and control, combined with new energy harvesting single Li-ion cell 26

technology, has made it possible to produce completely autonomous systems that are powered by local ambient energy

passive mixers increase instead of batteries. Powering a wireless sensor node from ambient gain and decrease noise in

or “free” energy is attractive because it can supplement or eliminate

downconverter apps 39

the need for batteries or wires. This is a clear benefit when battery replacement or servicing is inconvenient, costly or dangerous.

A complete lack of wires also makes it easy to expand monitor- ing and control systems on a large scale. Energy harvesting wire- less sensor systems simplify installation and maintenance in such diverse areas as building automation, wireless/automated metering and predictive maintenance, as well as numerous other industrial, military, automotive and consumer applications.

CONNECTOR WIRING DROPS CONNECTOR POWER DROPS DROPS

SUPPLY

The benefits of energy harvesting are clear, but an effec- tive energy harvesting system requires a clever power manage-

CONNECTOR WIRING DROPS CONNECTOR DROPS DROPS

ment scheme to convert the miniscule levels of free energy into a form usable by the wireless sensor system.

Figure 1. The simplest model for load regulation over

IT’S ALL ABOUT THE DUTY CYCLE

resistive interconnections.

Many wireless sensor systems consume very low average power, making them prime candidates to be powered by energy harvest- ing techniques. Many sensor nodes are used to monitor physical quantities that change slowly. Measurements can therefore be taken and transmitted infrequently, resulting in a low duty cycle of opera- tion and a correspondingly low average power requirement.

(continued on page 2)

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Page Summary Contents For LINEAR LTC3108 User Guide

Page 1 October 2010 Volume 20 Number 3 Ultralow Voltage Energy Harvester Uses Thermoelectric Generator for 4- and 6-supply monitors Battery-Free Wireless Sensors feature ±1.5% accuracy for David Salerno rail...
Page 2 …continued from the cover The missing link in the energy harvesting system chain In this issue... has been the power converter/power management COVER STORY block that can operate from one or more of t...
Page 3 An ideal power management solution for energy harvesting should be small, easy to apply and perform well from the exceptionally high or low voltages produced by common energy harvesting sources. (LTC3...
Page 4 cover story Figure 4. TEG construction CERAMIC SUBSTRATE P-TYPE CONDUCTOR SEMICONDUCTOR NEGATIVE(–) TABS PELLETS N-TYPE SEMICONDUCTOR power the IC (via the VAUX pin) and charge PELLETS POSITIVE(+) the...
Page 5 A good rule of thumb when selecting a thermoelectric module for power generation purposes is to choose the module with the highest product of (VMAX • IMAX) for a given size. RSOURCE = 1Ω UT (m LOAD OR...
Page 6 cover story IN (m A) The LTC3109 is uniquely suited to the challenge of harvesting energy from sources of either polarity. Using transformers with a step-up ratio of 1:100, it can operate from input v...
Page 7 AMBIENT TEMPERATURE in applications where a relatively small so a 1:50 transformer ratio was chosen for heat sink is used on one side of the TEG, the highest output power in the range of a larger TEG ...
Page 8 cover story UT (m With their unique ability to operate at input voltages as low as 20m V, or from very low voltages of either polarity, the LTC3108 and LTC3109 provide simple, effective power manageme...
Page 9 ZETEX T1 1n F ZC2811E C1 VSTORE TEG 3V CIN LTC3108-1 (THERMOELECTRIC GENERATOR) LITHIUM FERROTEC 9500/127/100B BATTERY VOUT2 200µA MAXPGD µP SW VLDO 2.2µF SENSORS VS2 VOUT VAUX RF LINK Figure 14. Ener...
Page 10 UT (m cover story T1 68n F TEG 1:100 C1A VOUT2 (THERMOELECTRIC GENERATOR) FERROTEC 9500/097/090B CIN 1n F LTC3109 30mm × 30mm 47µF C2A VOUT 330k 5V COUT SWA VLDO 2.2V VINA 2.2µF C1B C2B SWB PG00D PG00...

Manual Details

Brand Linear
Pages 10
File Size 1.67 MB
Published June 16, 2026
2 views

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Frequently Asked Questions

What are common sources used for energy harvesting?

The most common sources include vibration/motion, light, and heat.

How reliable is power from harvested energy sources?

Transducers produce unregulated output that may not provide a continuous or uninterrupted source of power.

What is the technical challenge addressed by these specialized converters?

They convert miniscule levels of free energy into a usable form for wireless sensor systems.

Does the LTC3109 support different operating modes?

It can be configured for unipolar operation, using a single transformer to satisfy various requirements.