LTC3109
APPLICATIONS INFORMATION
TEG LOꢃD MꢃTCꢄIꢁG
UꢁIPOLꢃR ꢃPPLICꢃTIOꢁS
The LTC3109 was designed to present an input resistance
(load) in the range of 2Ω to 10Ω, depending on input volt-
age,transformerturnsratioandtheC1AandC2Acapacitor
values (as shown in the Typical Performance curves). For
a given turns ratio, as the input voltage drops, the input
resistance increases. This feature allows the LTC3109 to
optimize power transfer from sources with a few Ohms
of source resistance, such as a typical TEG. Note that a
lower source resistance will always provide more output
current capability by providing a higher input voltage
under load.
The LTC3109 can also be configured to operate from two
independent unipolar voltage sources, such as two TEGs
in different locations. In this configuration, energy can be
harvestedfromeitherorbothsourcessimultaneously.See
the Typical Applications for an example.
The LTC3109 can also be configured to operate from a
singleunipolarsource,usingasinglestep-uptransformer,
by ganging its V and SW pins together. In this manner,
IN
it can extract the most energy from very low resistance
sources. See Figure 3 for an example of this configuration,
along with the performance curves.
Table ±. Peltier Cell ManufaAturers
PELTIER CELL (TEG) SUPPLIERS
CUI Inc
www.cui.com
Peltiercellsareavailableinawiderangeofsizesandpower
capabilities, from less than 10mm square to over 50mm
square. They are typically 2mm to 5mm in height. A list
of some Peltier cell manufacturers is given in Table 3 and
some recommended part numbers in Table 4.
Ferrotec
www.ferrotec.com/products/thermal/modules/
Fujitaka
www.fujitaka.com/pub/peltier/english/thermoelectric_power.html
Hi-Z Technology
www.hi-z.com
Kryotherm
COMPOꢁEꢁT SELECTIOꢁ
Step-Up Transformer
www.kryotherm
Laird Technologies
www.lairdtech.com
Micropelt
www.micropelt.com
The turns ratio of the step-up transformers will determine
how low the input voltage can be for the converter to start.
Duetotheauto-polarityarchitecture,twoidenticalstep-up
transformersshouldbeused,unlessthetemperaturedrop
across the TEG is significantly different in one polarity, in
which case the ratios may be different.
Nextreme
www.nextreme.com
TE Technology
www.tetech.com/Peltier-Thermoelectric-Cooler-Modules.html
Tellurex
www.tellurex.com/
Table 4. ReAommenꢂeꢂ TEG Part ꢁumbers by Size
MꢃꢁUFꢃCTURER
CUI Inc. (Distributor)
Ferrotec
ꢀ5mm
23mm
±3mm
43mm
CP85438
CP60133
CP60233
CP60333
9501/031/030 B
FPH13106NC
9501/071/040 B
FPH17106NC
9500/097/090 B
FPH17108AC
TGM-127-1.0-0.8
PT6.7.F2.3030.W6
RC6-6-01
9500/127/100 B
FPH112708AC
LCB-127-1.4-1.15
PT8.12.F2.4040.TA.W6
RC12-8-01LS
Fujitaka
Kryotherm
Laird Technology
Marlow Industries
Tellurex
RC3-8-01
C2-20-0409
C2-15-0405
C2-30-1505
C2-40-1509
TE Technology
TE-31-1.0-1.3
TE-31-1.4-1.15
TE-71-1.4-1.15
TE-127-1.4-1.05
3109fa
13
Linear Systems [ Linear Systems ]
