
LTC3400/LTC3400B
7
3400f
Table 1. Recommended Inductors
MAX
DCR
m
57
124
105
170
109
182
216
174
60
75
90
84
137
L
HEIGHT
(mm)
2.0
2.0
1.8
1.8
3.5
3.5
0.8
0.8
2.9
2.9
2.9
2.0
2.0
PART
CDRH5D18-4R1
CDRH5D18-100
CDRH3D16-4R7
CDRH3D16-6R8
CR43-4R7
CR43-100
CMD4D06-4R7MC
CMD4D06-3R3MC
DS1608-472
DS1608-103
DO1608C-472
D52LC-4R7M
D52LC-100M
(
μ
H)
4.1
10
4.7
VENDOR
Sumida
(847) 956-0666
www.sumida.com
4.7
10
4.7
3.3
4.7
10
4.7
4.7
10
Coilcraft
(847) 639-6400
www.coilcraft.com
Toko
(408) 432-8282
www.tokoam.com
Murata
www.murata.com
LQH3C4R7M24
4.7
195
2.2
Output and Input Capacitor Selection
Low ESR (equivalent series resistance) capacitors should
be used to minimize the output voltage ripple. Multilayer
ceramic capacitors are an excellent choice as they have
extremely low ESR and are available in small footprints. A
2.2
μ
F to 10
μ
F output capacitor is sufficient for most
applications. Larger values up to 22
μ
F may be used to
obtain extremely low output voltage ripple and improve
transient response. An additional phase lead capacitor
may be required with output capacitors larger than 10
μ
F
APPLICATIOU
W
U
U
to maintain acceptable phase margin. X5R and X7R
dielectric materials are preferred for their ability to main-
tain capacitance over wide voltage and temperature ranges.
Low ESR input capacitors reduce input switching noise
and reduce the peak current drawn from the battery. It
follows that ceramic capacitors are also a good choice for
input decoupling and should be located as close as pos-
sible to the device. A 4.7
μ
F input capacitor is sufficient for
virtually any application. Larger values may be used with-
out limitations. Table 2 shows a list of several ceramic
capacitor manufacturers. Consult the manufacturers di-
rectly for detailed information on their entire selection of
ceramic parts.
Table 2. Capacitor Vendor Information
SUPPLIER
AVX
Murata
Taiyo Yuden
PHONE
(803) 448-9411
(714) 852-2001
(408) 573-4150
WEBSITE
www.avxcorp.com
www.murata.com
www.t-yuden.com
Output Diode
Use a Schottky diode such as an MBR0520L, CMDSH2-3,
1N5817 or equivalent if the converter output voltage is 4.5V
or greater. The Schottky diode carries the output current for
the time it takes for the synchronous rectifier to turn on. Do
not use ordinary rectifier diodes, since the slow recovery
times will compromise efficiency. A Schottky diode is
optional for output voltages below 4.5V, but will increase
converter efficiency by 2% to 3%.