Datasheet
LTC3108-1
18
31081fb
For more information www.linear.com/LTC3108-1
Peltier-Powered Energy Harvester for Remote Sensor Applications
31081 TA02
C1
C2
SW
VS2
VS1
COOPER BUSSMAN PB-5ROH104-R
OR KR-5R5H104-R
V
OUT2
V
OUT2
PGOOD
2.2V
499k
C
OUT
*
PGD
VLDO
VSTORE
+
V
OUT
V
OUT2_EN
LTC3108-1
VAUX GND
C
STORE
0.1F
6.3V
5.25V
3V
1µF
1nF
C
IN
1:100
T1
T1: COILCRAFT LPR6235-752SML
*C
OUT
VALUE DEPENDENT ON
THE MAGNITUDE AND DURATION
OF THE LOAD PULSE
330pF
∆T = 1°C TO 20°C
SENSORS
XMTR
µP
2.2µF
ON
OFF
3V
+
+
+
THERMOELECTRIC
GENERATOR
Typical applicaTions
If there were 50µA of charge current available and 5µA of
load on V
OUT
, the time for V
OUT
to reach regulation after
the initial application of power would be 11.35 seconds.
Design Example 2
In many pulsed load applications, the duration, magnitude
and frequency of the load current bursts are known and
fixed. In these cases, the average charge current required
from the LTC3108-1 to support the average load must be
calculated, which can be easily done by the following:
I
CHG
≥ I
Q
+
I
BURST
• t
T
Where I
Q
is the sleep current on V
OUT
required by the ex-
ternal circuitry in between bursts (including cap leakage),
I
BURST
is the total load current during the burst, t is the
duration of the burst and T is the period of the transmit
burst rate (essentially the time between bursts).
In this example, I
Q
= 5µA, I
BURST
= 100mA, t = 5ms and
T = one hour. The average charge current required from
the LTC3108-1 would be:
I
CHG
≥ 5µA +
100mA • 0.005sec
3600sec
= 5.14µA
Therefore, if the LTC3108-1 has an input voltage that al-
lows it to supply a charge current greater than 5.14µA, the
application can support 100mA bursts lasting 5ms every
hour. It can be determined that the sleep current of 5µA is
the dominant factor because the transmit duty cycle is so
small (0.00014%). Note that for a V
OUT
of 3V, the average
power required by this application is only 15.4µW (not
including converter losses).
Note that the charge current available from the LTC3108-1
has no effect on the sizing of the V
OUT
capacitor (if it is
assumed that the load current during a burst is much larger
than the charge current), and the V
OUT
capacitor has no
effect on the maximum allowed burst rate.
applicaTions inForMaTion