LTC3621 datasheet(11/16 Pages) LINER

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LTC3621/LTC3621-2

3621f

For more information www.linear.com/LTC3621

applicaTions inForMaTion

produce the most improvement. Percent efficiency can

be expressed as:

% Efficiency = 100% – (L1 + L2 + L3 +…)

where L1, L2, etc. are the individual losses as a percent-

age of input power. Although all dissipative elements in

the circuit produce losses, three main sources usually

account for most of the losses in LTC3621 circuits: 1) I2R

losses, 2) switching and biasing losses, 3) other losses.

1. I2R losses are calculated from the DC resistances of

the internal switches, RSW, and external inductor, RL.

In continuous mode, the average output current flows

through inductor L but is “chopped” between the

internal top and bottom power MOSFETs. Thus, the

series resistance looking into the SW pin is a function

of both top and bottom MOSFET RDS(ON) and the duty

cycle (DC) as follows:

RSW = (RDS(ON)TOP)(DC) + (RDS(ON)BOT)(1 – DC)

TheRDS(ON)forboththetopandbottomMOSFETscanbe

obtained from the Typical Performance Characteristics

curves. Thus to obtain I2R losses:

I2R losses = IOUT2(RSW + RL)

Table 1. Inductor Selection Table

INDUCTOR

INDUCTANCE

(µH)

DCR

(mΩ)

MAX CURRENT

(A)

DIMENSIONS

(mm)

HEIGHT

(mm)

MANUFACTURER

IHLP-1616BZ-11 Series

1.0

2.2

4.7

4.5

3.25

1.7

4.3 × 4.7

Vishay

www.vishay.com

IHLP-2020BZ-01 Series

2.2

3.3

4.7

5.6

6.8

18.9

45.6

79.2

108

113

139

4.2

3.3

2.8

2.5

2.4

5.4 × 5.7

FDV0620 Series

2.2

3.3

4.7

5.7

3.2

2.8

6.7 × 7.4

Toko

www.toko.com

MPLC0525L Series

1.5

2.2

6.4

5.2

4.1

6.2 × 5.4

2.5

NEC/Tokin

www.nec-tokin.com

HCP0703 Series

1.5

2.2

3.3

4.7

6.8

8.2

5.5

4.5

7 × 7.3

Cooper Bussmann

www.cooperbussmann.com

RLF7030 Series

1.5

2.2

3.3

4.7

6.8

8.8

9.6

6.4

6.1

5.4

4.1

3.4

2.8

6.9 × 7.3

3.2

TDK

www.tdk.com

WE-TPC 4828 Series

1.2

1.8

2.2

2.7

3.3

3.9

4.7

3.1

2.7

2.5

2.35

2.15

1.72

1.55

4.8 × 4.8

2.8

Würth Elektronik

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