LT1376 Просмотр технического описания (PDF) - Linear Technology
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LT1376 Datasheet PDF : 28 Pages
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LT1375/LT1376
APPLICATIONS INFORMATION
5. After making an initial choice, consider the secondary
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.
Table 2
VENDOR/
PART NO.
Coiltronics
CTX5-1
CTX10-1
CTX20-1
CTX15-2
CTX20-3
CTX20-4
CTX5-1P
CTX10-1P
CTX15-1P
CTX20-1P
CTX20-2P
CTX20-4P
Sumida
CDRH64
CDRH74
CDRH73
CDRH73
CD73
CD73
CD104
CD104
Gowanda
SM20-102K
SM20-152K
SM20-222K
Dale
IHSM-4825
IHSM-4825
IHSM-5832
IHSM-5832
IHSM-7832
VALUE DC CORE
(µH) (Amps) TYPE
5 2.3 Tor
10 1.9 Tor
20 1.0 Tor
15 1.8 Tor
20 1.5 Tor
20 2.2 Tor
5 1.8 Tor
10 1.6 Tor
15 1.2 Tor
20 1.0 Tor
20 1.3 Tor
20 1.8 Tor
10 1.7 SC
22 1.2 SC
10 1.7 SC
22 1.1 SC
10 1.4 Open
18 1.1 Open
10 2.4 Open
18 1.7 Open
10 1.3 Open
15 1.3 Open
22 1.3 Open
10 3.1 Open
22 1.7 Open
10 4.3 Open
22 2.8 Open
22 3.8 Open
SERIES CORE
RESIS- MATER- HEIGHT
TANCE(Ω) IAL (mm)
0.027
0.039
0.137
0.058
0.093
0.059
0.021
0.030
0.046
0.081
0.052
0.039
KMµ 4.2
KMµ 4.2
KMµ 4.2
KMµ 6.0
KMµ 4.7
KMµ 6.4
52
4.2
52
4.2
52
4.2
52
4.2
52
6.0
52
6.35
0.084
Fer
4.5
0.077
Fer
4.5
0.055
Fer
3.4
0.15
Fer
3.4
0.062
Fer
3.5
0.085
Fer
3.5
0.041
Fer
4.0
0.062
Fer
4.0
0.038
Fer
7.0
0.049
Fer
7.0
0.059
Fer
7.0
0.071
Fer
5.6
0.152
Fer
5.6
0.053
Fer
7.1
0.12
Fer
7.1
0.054
Fer
7.1
Tor = Toroid
SC = Semi-closed geometry
Fer = Ferrite core material
52 = Type 52 powdered iron core material
KMµ = Kool Mµ
Output Capacitor
The output capacitor is normally chosen by its Effective
Series Resistance (ESR), because this is what determines
output ripple voltage. At 500kHz, any polarized capacitor
is essentially resistive. To get low ESR takes volume, so
physically smaller capacitors have high ESR. The ESR
range for typical LT1376 applications is 0.05Ω to 0.5Ω. A
typical output capacitor is an AVX type TPS, 100µF at 10V,
with a guaranteed ESR less than 0.1Ω. This is a “D” size
surface mount solid tantalum capacitor. TPS capacitors
are specially constructed and tested for low ESR, so they
give the lowest ESR for a given volume. The value in
microfarads is not particularly critical, and values from
22µF to greater than 500µF work well, but you cannot
cheat mother nature on ESR. If you find a tiny 22µF solid
tantalum capacitor, it will have high ESR, and output ripple
voltage will be terrible. Table 3 shows some typical solid
tantalum surface mount capacitors.
Table 3. Surface Mount Solid Tantalum Capacitor ESR
and Ripple Current
E Case Size
ESR (Max., Ω) Ripple Current (A)
AVX TPS, Sprague 593D
0.1 to 0.3
0.7 to 1.1
AVX TAJ
0.7 to 0.9
0.4
D Case Size
AVX TPS, Sprague 593D
0.1 to 0.3
0.7 to 1.1
AVX TAJ
0.9 to 2.0
0.36 to 0.24
C Case Size
AVX TPS
0.2 (typ)
0.5 (typ)
AVX TAJ
1.8 to 3.0
0.22 to 0.17
B Case Size
AVX TAJ
2.5 to 10
0.16 to 0.08
Many engineers have heard that solid tantalum capacitors
are prone to failure if they undergo high surge currents.
This is historically true, and type TPS capacitors are
specially tested for surge capability, but surge ruggedness
is not a critical issue with the output capacitor. Solid
tantalum capacitors fail during very high turn-on surges,
which do not occur at the output of regulators. High
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