LTC3554 LINER [Linear Technology], LTC3554 Datasheet - Page 24

• Manufacturer Part Number: LTC3554
• Description: Micropower USB Power Manager with Li-Ion Charger and Two Step-Down Regulators
• Manufacturer: LINER [Linear Technology]

LTC3554
OPERATION
Inductor value should be chosen based on the desired
output voltage. See Table 2. Table 3 shows several
inductors that work well with the step-down switching
regulators. These inductors offer a good compromise
in current rating, DCR and physical size. Consult each
manufacturer for detailed information on their entire
selection of inductors.
Larger value inductors reduce ripple current, which
improves output ripple voltage. Lower value inductors
result in higher ripple current and improved transient
response time, but will reduce the available output cur-
rent. To maximize effi ciency, choose an inductor with a
low DC resistance.
Table 1. Ceramic Capacitor Manufacturers
AVX
Murata
Taiyo Yuden
Vishay Siliconix
TDK
Table 3. Recommended Inductors for Step-Down Switching Regulators
INDUCTOR PART NO.
1117AS-4R7M
1117AS-6R8M
1117AS-100M
CDRH2D11BNP-4R7N
CDRH2D11BNP-6R8N
CDRH2D11BNP-100N
SD3112-4R7-R
SD3112-6R8-R
SD3112-100-R
EPL2014-472ML_
EPL2014-682ML_
EPL2014-103ML_
* = Typical DCR
24
www.avxcorp.com
www.murata.com
www.t-yuden.com
www.vishay.com
www.tdk.com
L (μH)
4.7
6.8
4.7
6.8
4.7
6.8
4.7
6.8
10
10
10
10
MAX I
0.64
0.54
0.45
0.48
0.68
0.55
0.88
0.7
0.6
0.8
0.8
0.6
DC
(A)
MAX DCR (Ω)
Choose an inductor with a DC current rating at least 1.5
times larger than the maximum load current to ensure that
the inductor does not saturate during normal operation.
If output short circuit is a possible condition, the induc-
tor should be rated to handle the maximum peak current
specifi ed for the step-down converters.
Different core materials and shapes will change the size/cur-
rent and price/current relationship of an inductor. Toroid
or shielded pot cores in ferrite or permalloy materials
are small and do not radiate much energy, but generally
cost more than powdered iron core inductors with similar
electrical characteristics. Inductors that are very thin or
have a very small volume typically have much higher core
Table 2. Choosing the Inductor Value
DESIRED OUTPUT VOLTAGE
1.8V or Less
1.8V to 2.5V
2.5V to 3.3V
0.250*
0.380*
0.446*
0.246*
0.291*
0.248
0.284
0.428
0.254
0.316
0.416
0.18*
SIZE (L × W × H) (mm) MANUFACTURER
3.0 × 2.8 × 1.0
3.0 × 3.0 × 1.2
3.1 × 3.1 × 1.2
2.0 × 1.8 × 1.4
RECOMMENDED INDUCTOR VALUE
10μH
6.8μH
4.7μH
Toko
www.toko.com
Sumida
www.sumida.com
Cooper
www.cooperet.com
Coilcraft
www.coilcraft.com
3554f