LTC3108

16

3108p

APPLICATIONS INFORMATION

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 to support the average load must be

calculated, which can be easily done by the following:

II

It

T

CHG

Q

BURST

≥ +

•

ternal circuitry in between bursts (including cap leakage),

duration of the burst and T is the period of the transmit

burst rate (essentially the time between bursts).

T = one hour. The average charge current required from

the LTC3108 would be:

IµA

mA

µA

+=

5

100

0 005

3600

514

•

.

sec

sec

.

Therefore, if the LTC3108 has an input voltage that allows

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

average power required by this application is only 17μW

(not including converter losses).

Note that the charge current available from the LTC3108

assumed that the load current during a burst is much larger

effect on the maximum allowed burst rate.

Peltier-Powered Energy Harvester for Remote Sensor Applications

TEG

3108 TA02

C1

C2

SW

VS2

VS1

COOPER BUSSMAN PB-5ROH104-R

OR KR-5R5H104-R

PGOOD

2.2V

PGD

VLDO

VSTORE

+

LTC3108

VAUX

GND

0.1F

6.3V

5V

3.3V

1μF

1nF

1:100

T1

T1: COILCRAFT LPR6235-752SML

330pF

ΔT = 1°C TO 20°C

SENSORS

XMTR

μP

2.2μF

ON

OFF

3.3V

+

+

+

TYPICAL APPLICATIONS