LTC3459ES6TRMPBF Datasheet, PDF (8/12 Pages) Linear Technology – 10V Micropower Synchronous Boost Converter

LTC3459
OPERATION
This is accomplished by varying the t_OFF period by ap-
proximately 1/(V_OUT – V_IN). Due to propagation delays
and a 0.6μA bias current in the timer, the t_OFF time can be
more accurately predicted as follows:
t_OFF
≈
100ns
+
0.8pF • 1.25V
0.6μA + ^{VOUT – VIN}
500k
If V_OUT is less than V_IN, the t_OFF delay is fixed at approxi-
mately 750ns.
APPLICATIONS INFORMATION
Inductor Selection
An inductor with a minimum value of 15μH is recommended
for use with the LTC3459. Values larger than 15μH will
result in lower ripple current and switching frequency.
High frequency ferrite core materials are strongly recom-
mended. Some inductors meeting these requirements are
listed in Table 1.
Table 1. Example Inductors
VENDOR/PART
Chip Inductors
L DCR (Ω)/ DIMENSIONS CONTACT
(μH) I_MAX (mA)
(mm)
INFORMATION
Murata
LQH31C
22
LQH32C-Low Profile 22
www.murata.com
3/160 3.2 × 1.6 × 1.8
0.7/250 3.2 × 2.5 × 1.6
Taiyo Yuden
LB2016
www.t-yuden.com
15 0.7/130 2.0 × 1.6 × 1.6 [phone]
22 1/105
33 1.7/85
Toko
LLB2520
www.tokoam.com
15 1.7/180 2.5 × 2.0 × 1.6 [phone]
22 2.5/160
33 3.8/130
Coilcraft
DO3314
DO1606T
www.coilcraft.com
15 0.86/650 3.3 × 3.3 × 1.4 [phone]
22 1.2/500
15 0.4/700 6.5 × 5.3 × 2.0
22 0.5/500
33 0.74/450
Sumida
CMD4D06
CDRJ2D1BLD
www.sumida.com
15 0.5/400 6.6 × 5.8 × 0.8 [phone]
22 0.8/300
33 1.3/240
15 0.175/350 3.2 × 3.2 × 2.0
22 0.255/300
33 0.37/240
8
Capacitor Selection
The boost converter requires two capacitors. The input
capacitor should be an X5R type of at least 1.0μF. The V_OUT
capacitor should also be an X5R type between 2.2μF and
10μF. A larger capacitor should be used if lower peak-to-
peak output ripple and better line regulation is desired.
Table 2. Capacitor Vendor Information
SUPPLIER
PHONE
AVX
[phone]
Murata
[phone]
Taiyo Yuden
[phone]
TDK
[phone]
WEBSITE
www.avxcorp.com
www.murata.com
www.t-yuden.com
www.component.tdk.com
PCB Layout Guidelines
The high speed operation of the LTC3459 demands care-
ful attention to board layout. You will not get advertised
performance with a careless layout. Figure 4 shows the
recommended component placement for the TSOT ver-
sion of the part. A large ground pin copper area will help
to lower the chip temperature.
RECOMMENDED COMPONENT
PLACEMENT. TRACES CARRYING
CURRENT ARE DIRECT. TRACE
AREA AT FB PIN IS SMALL. LEAD
LENGTH TO BATTERY IS SHORT
V_IN
1 SW V_IN 6
2 GND V_OUT 5
3 FB SHDN 4
SHDN
V_OUT
3459 F04
Figure 4. Recommended Component
Placement for a Single-Layer Board
3459fc