LTC3306CACBZ-R7 datasheet(10/16 Pages) AD

10 / 16 page

LTC3306

Rev. 0

For more information www.analog.com

APPLICATIONS INFORMATION

Refer to the Block Diagram for reference.

Inductor Selection and Maximum Output Current

Considerations in choosing an inductor are inductance,

RMS current rating, saturation current rating, DCR, and

core loss.

If the duty cycle of operation is 50% or less choose the

inductor based on Equation 1.

L ≈

VOUT

0.3 •IMAX • fSW

• 1

−

VOUT

VIN(MAX)

⎛

⎝

⎜

⎞

⎠

⎟

(1)

where fSW is the switching frequency and IMAX is 1.75A, the

maximum rated load current for the LTC3306. For opera-

tion at duty cycles higher than 50%, use Equation 2 to

select the inductor.

L ≈

VIN(MAX)

0.3 •IMAX • 4 • fSW

(2)

To avoid overheating of the inductor, choose an inductor

with an RMS current rating that is greater than the maxi-

mum expected output load of the application. Overload

and short-circuit conditions may need to be taken

into consideration.

The saturation current rating (typically labeled ISAT) of

the inductor must be higher than the maximum expected

load current plus half the inductor ripple current (see

Equation 3).

ISAT >ILOAD MAX

(

) +

∆IL

(3)

where ILOAD(MAX) is the maximum output load current for

a given application and ΔIL is the inductor ripple current

calculated using Equation 4.

∆IL =

VOUT

L • fSW

• 1–

VOUT

VIN

⎛

⎝⎜

⎞

⎠⎟

(4)

A more conservative choice would be to use an inductor

with an ISAT rating higher than the maximum current limit

of the LTC3306.

To keep the efficiency high, choose an inductor with low

series resistance (DCR). The core material should be

intended for high frequency applications. Table 1 shows

recommended inductors from several manufacturers.

Table 1. Recommended Inductors

MANUFACTURER

FAMILY

L (nH)

MAX IDC (A)

MAX DCR (mΩ)

SIZE IN mm (L × W × H)

Murata

DFE18SAN_E0

470 to 1000

2 to 3.1

64 to 144

1.6 × 0.8 × 0.8

Murata

DFE18SAN_G0

470 to 1000

2.1 to 3.3

54 to 128

1.6 × 0.8 × 1.0

Murata

DFE201210U

470 to 1000

3.1 to 4.4

42 to 95

2.0 × 1.2 × 1.0

Murata

DFE201612E

470 to 1000

4.0 to 5.5

26 to 48

2.0 × 1.6 × 1.2

TDK

TFM160808ALC

470

2.9

1.6 × 0.8 × 0.8

Taiyo Yuden

MCHK1608

470 to 1000

2.2 to 3.3

43 to 110

1.6 × 0.8 × 0.8

Taiyo Yuden

MCHK2012

470 to 1000

2.26 to 3.21

36 to 111

2.0 × 1.2 × 0.8

Taiyo Yuden

MCKK2012

470 to 1000

3.6 to 4.5

39 to 90

2.0 × 1.2 × 1.0

Littlefuse

LPWI1608

470 to 1000

2.0 to 3.4

45 to 150

1.6 × 0.8 × 0.8

Littlefuse

LPWI201208

470 to 1000

3.4 to 5.0

35 to 65

2.0 × 1.2 × 0.8

Littlefuse

LPWI201210

470 to 1000

3.5 to 5.4

28 to 60

2.0 × 1.2 × 1.0

Wurth Elektronik

74479262147

470

1.5

1.6 × 0.8 × 0.8

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