LTC3108EGN-1#PBF Linear Technology, LTC3108EGN-1#PBF Datasheet - Page 12

• Manufacturer Part Number: LTC3108EGN-1#PBF
• Description: IC VOLTAGE CONVERTER 16-SSOP
• Manufacturer: Linear Technology

Specifications of LTC3108EGN-1#PBF

• Applications: Energy Harvesting
• Current - Supply: 3mA
• Voltage - Supply: 20mV ~ 500mV
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

applicaTions inForMaTion
LTC3108-1
Introduction
The LTC3108-1 is designed to gather energy from very
low input voltage sources and convert it to usable output
voltages to power microprocessors, wireless transmitters
and analog sensors. Such applications typically require
much more peak power, and at higher voltages, than
the input voltage source can produce. The LTC3108-1 is
designed to accumulate and manage energy over a long
period of time to enable short power bursts for acquiring
and transmitting data. The bursts must occur at a low
enough duty cycle such that the total output energy dur-
ing the burst does not exceed the average source power
integrated over the accumulation time between bursts.
For many applications, this time between bursts could
be seconds, minutes or hours.
The PGD signal can be used to enable a sleeping micro-
processor or other circuitry when V
indicating that enough energy is available for a burst.
Input Voltage Sources
The LTC3108-1 can operate from a number of low input
voltage sources, such as Peltier cells, photovoltaic cells or
thermopile generators. The minimum input voltage required
for a given application will depend on the transformer
turns ratio, the load power required, and the internal DC
resistance (ESR) of the voltage source. Lower ESR will
allow the use of lower input voltages, and provide higher
output power capability.

Figure 2. Typical Performance of a Peltier Cell Acting as a Thermoelectric Generator
OUT
reaches regulation,
1000
100
10
1
1
TEG: 30mm
127 COUPLES
R = 2
MAX P
(IDEAL)
dT (°C)
V
10
OC
OUT
Refer to the I
Characteristics section to see what input current is required
for the source for a given input voltage.
For a given transformer turns ratio, there is a maximum
recommended input voltage to avoid excessively high
secondary voltages and power dissipation in the shunt
regulator. It is recommended that the maximum input
voltage times the turns ratio be less than 50.
Note that a low ESR bulk decoupling capacitor will usually
be required across the input source to prevent large voltage
droop and ripple caused by the source’s ESR and the peak
primary switching current (which can reach hundreds of
milliamps). The time constant of the filter capacitor and
the ESR of the voltage source should be much longer than
the period of the resonant switching frequency.
Peltier Cell (Thermoelectric Generator)
A Peltier cell (also known as a thermoelectric cooler) is
made up of a large number of series-connected P-N junc-
tions, sandwiched between two parallel ceramic plates.
Although Peltier cells are often used as coolers by apply-
ing a DC voltage to their inputs, they will also generate
a DC output voltage, using the Seebeck effect, when the
two plates are at different temperatures. The polarity of
the output voltage will depend on the polarity of the tem-
perature differential between the plates. The magnitude of
the output voltage is proportional to the magnitude of the
temperature differential between the plates. When used in
100
31081 F02
100
10
1
0.1
IN
vs V
IN
curves in the Typical Performance
31081f