LT1374C Linear Technology, LT1374C Datasheet - Page 11

• Manufacturer Part Number: LT1374C
• Description: 4.5A/ 500kHz Step-Down Switching Regulator
• Manufacturer: Linear Technology

APPLICATIONS
3. Decide if the design can tolerate an “open” core geom-
4. Start shopping for an inductor (see representative
5. After making an initial choice, consider the secondary
saturate abruptly. Other core materials fall somewhere
in between. The following formula assumes continu-
ous mode of operation, but it errs only slightly on the
high side for discontinuous mode, so it can be used for
all conditions.
V
f = Switching frequency, 500kHz
etry like a rod or barrel, with high magnetic field
radiation, or whether it needs a closed core like a toroid
to prevent EMI problems. One would not want an open
core next to a magnetic storage media, for instance!
This is a tough decision because the rods or barrels are
temptingly cheap and small and there are no helpful
guidelines to calculate when the magnetic field radia-
tion will be a problem.
surface mount units in Table 2) which meets the
requirements of core shape, peak current (to avoid
saturation), average current (to limit heating), and fault
current (if the inductor gets too hot, wire insulation will
melt and cause turn-to-turn shorts). Keep in mind that
all good things like high efficiency, low profile, and high
temperature operation will increase cost, sometimes
dramatically. Get a quote on the cheapest unit first to
calibrate yourself on price, then ask for what you really
want.
things like output voltage ripple, second sourcing, etc.
Use the experts in the Linear Technology’s applica-
tions department if you feel uncertain about the final
choice. They have experience with a wide range of
inductor types and can tell you about the latest devel-
opments in low profile, surface mounting, etc.
IN
I
PEAK
= Maximum input voltage
I
OUT
U
V
OUT
2
INFORMATION
U
f L V
V
IN
V
IN
OUT
W
U
Table 2
VENDOR/
PART NO.
Coiltronics
CTX2-1
CTX5-4
CTX8-4
CTX2-1P
CTX2-3P
CTX5-4P
Sumida
CDRH125
CDRH125
CDRH125
CDRH125
Coilcraft
DT3316-222
DT3316-332
DT3316-472
Pulse
PE-53650
PE-53651
PE-53652
PE-53653
Dale
IHSM-4825
IHSM-4825
IHSM-5832
IHSM-5832
IHSM-7832
Tor = Toroid
SC = Semi-closed geometry
Fer = Ferrite core material
52 = Type 52 powdered iron core material
KM = Kool M
VALUE
( H)
2.2
3.3
4.7
2.7
4.7
10
12
15
18
16
10
15
22
2
5
8
2
2
5
4
5
9
(Amps)
4.1
4.4
3.5
3.4
4.6
3.3
4.0
3.5
3.3
3.0
4.8
5.4
5.5
5.1
5.1
4.0
4.3
3.5
3.8
DC
5
5
3
CORE
TYPE
Open
Open
Open
Open
Open
Tor
Tor
Tor
Tor
Tor
Tor
Tor
Tor
Tor
Tor
SC
SC
SC
SC
SC
SC
SC
TANCE( )
SERIES
RESIS-
0.011
0.019
0.020
0.014
0.012
0.027
0.025
0.027
0.030
0.034
0.035
0.040
0.045
0.017
0.018
0.022
0.032
0.034
0.047
0.053
0.078
0.054
MATER- HEIGHT
CORE
KM
KM
KM
IAL
Fer
Fer
Fer
Fer
Fer
Fer
Fer
Fer
Fer
Fer
Fer
Fer
Fer
Fer
Fer
Fer
52
52
52
LT1374
11
(mm)
4.2
6.4
6.4
4.2
4.8
6.4
5.1
5.1
5.1
9.1
9.1
5.6
5.6
7.1
7.1
7.1
10
10
6
6
6
6