LTC3108EDE-1#PBF Linear Technology, LTC3108EDE-1#PBF Datasheet - Page 16

• Manufacturer Part Number: LTC3108EDE-1#PBF
• Description: IC VOLTAGE CONVERTER 12-DFN
• Manufacturer: Linear Technology

Specifications of LTC3108EDE-1#PBF

• Applications: Energy Harvesting
• Current - Supply: 3mA
• Voltage - Supply: 20mV ~ 500mV
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 12-DFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

applicaTions inForMaTion
LTC3108-1
at times when the input power may be lost. Note that this
capacitor can charge all the way to 5.25V (regardless of
the settings for V
has a working voltage rating of at least 5.5V at the tem-
perature for which it will be used. The VSTORE capacitor
can be sized using the following:
Where 6µA is the quiescent current of the LTC3108-1, I
is the load on V
the LDO between bursts, I
the burst, t is the duration of the burst, f is the frequency
of the bursts, TSTORE is the storage time required and
V
To minimize losses and capacitor charge time, all capaci-
tors used for V
See Table 6 for recommended storage capacitors.
Table 6. Recommended Storage Capacitors
VENDOR
AVX
www.avx.com
Cap-XX
www.cap-xx.com
Cooper/Bussmann
www.bussmann.com/3/PowerStor.html
Vishay/Sprague
www.vishay.com/capacitors
Storage capacitors requiring voltage balancing are not
recommended due to the current draw of the balancing
resistors.

OUT
C
STORE
is the output voltage required.
≥
 
6
µA I
OUT
OUT
OUT
+
in between bursts, I
and VSTORE should be low leakage.
), so ensure that the holdup capacitor
Q
+
I
LDO
BURST
5
+
. . 25 − V
(
I
BURST
PART NUMBER/SERIES
BestCap Series
TAJ and TPS Series Tantalum
GZ Series
KR Series
P Series
Tantamount 592D
595D Tantalum
150CRZ/153CRV Aluminum
013 RLC (Low Leakage)
is the total load during
OUT
• • ) •
LDO
t f
is the load on
 
TSTORE
Q
PCB Layout Guidelines
Due to the rather low switching frequency of the resonant
converter and the low power levels involved, PCB layout
is not as critical as with many other DC/DC converters.
There are, however, a number of things to consider.
Due to the very low input voltage the circuit may operate
from, the connections to V
and the SW and GND pins of the LTC3108-1 should be
designed to minimize voltage drop from stray resistance
and able to carry currents as high as 500mA. Any small
voltage drop in the primary winding conduction path will
lower efficiency and increase capacitor charge time.
Also, due to the low charge currents available at the outputs
of the LTC3108-1, any sources of leakage current on the
output voltage pins must be minimized. An example board
layout is shown in Figure 3.
V
V
OUT2
OUT
31081 FO3
Figure 3. Example Component Placement for
Two-Layer PC Board (DFN Package)
VLDO
PGOOD
GND
VSTORE
V
VLDO
VAUX
V
OUT2
PGD
OUT
IN
1
2
3
4
5
6
, the primary of the transformer
VIAS TO GROUND PLANE
12
11
10
9
8
7
SW
C2
C1
V
VS1
VS2
OUT2_EN
V
IN
31081f