LTC3109_15 Datasheet, PDF (13/24 Pages) Linear Technology – Auto-Polarity, Ultralow Voltage Step-Up Converter and Power Manager

LTC3109
Applications Information
TEG Load Matching
The LTC3109 was designed to present an input resistance
(load) in the range of 2Ω to 10Ω, depending on input volt-
age, transformer turns ratio and the C1A and C2A capacitor
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.
Table 3. Peltier Cell Manufacturers
CUI Inc
www.cui.com
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
www.kryotherm
Laird Technologies
www.lairdtech.com
Micropelt
www.micropelt.com
Nextreme
www.nextreme.com
TE Technology
www.tetech.com/Peltier-Thermoelectric-Cooler-Modules.html
Tellurex
www.tellurex.com/
Unipolar Applications
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
harvested from either or both sources simultaneously. See
the Typical Applications for an example.
The LTC3109 can also be configured to operate from a
single unipolar source, using a single step-up transformer,
by ganging its V_IN and SW pins together. In this manner,
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.
Peltier Cell (TEG) Suppliers
Peltier cells are available in a wide range of sizes and power
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.
COMPONENT SELECTION
Step-Up Transformer
The turns ratio of the step-up transformers will determine
how low the input voltage can be for the converter to start.
Due to the auto-polarity architecture, two identical step-up
transformers should be used, unless the temperature drop
across the TEG is significantly different in one polarity, in
which case the ratios may be different.
Table 4. Recommended TEG Part Numbers by Size
MANUFACTURER
15mm
CUI Inc. (Distributor)
CP60133
Ferrotec
9501/031/030 B
Fujitaka
FPH13106NC
Kryotherm
Laird Technology
Marlow Industries
Tellurex
C2-15-0405
TE Technology
TE-31-1.0-1.3
20mm
CP60233
9501/071/040 B
FPH17106NC
RC3-8-01
C2-20-0409
TE-31-1.4-1.15
30mm
CP60333
9500/097/090 B
FPH17108AC
TGM-127-1.0-0.8
PT6.7.F2.3030.W6
RC6-6-01
C2-30-1505
TE-71-1.4-1.15
40mm
CP85438
9500/127/100 B
FPH112708AC
LCB-127-1.4-1.15
PT8.12.F2.4040.TA.W6
RC12-8-01LS
C2-40-1509
TE-127-1.4-1.05
For more information www.linear.com/LTC3109
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