2

IN

S

IN

S

V

V -V

L =

×

×

V

Iout_max×f

0.35

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æ

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æ

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(1)

Rectifier Diode Selection

avg

out

I

I

=

TPS61087

Typically, it is recommended that the inductor current ripple is below 20% of the average inductor current. The

following equation can therefore be used to calculate the inductor value:

Table 1. Inductor Selection

L

COMPONENT

SIZE

DCR TYP

SUPPLIER

Isat (A)

CODE

(

µH)

(L×W×H mm)

(m

Ω)

1.2 MHz

4.2

Sumida

CDRH5D28

5.7 × 5.7 × 3

23

2.2

4.7

Würth Elektronik

7447785004

5.9 × 6.2 × 3.3

60

2.5

5

Coilcraft

MSS7341

7.3 × 7.3 × 4.1

24

2.9

5

Sumida

CDRH6D28

7 × 7 × 3

23

2.4

4.6

Sumida

CDR7D28

7.6 × 7.6 × 3

38

3.15

4.7

Würth Elektronik

7447789004

7.3 × 7.3 × 3.2

33

3.9

3.3

Würth Elektronik

7447789003

7.3 × 7.3 × 3.2

30

4.2

650 kHz

10

Würth Elektronik

744778910

7.3 × 7.3 × 3.2

51

2.2

10

Sumida

CDRH8D28

8.3 × 8.3 × 3

36

2.7

6.8

Sumida

CDRH6D26HPNP

7 × 7 × 2.8

52

2.9

6.2

Sumida

CDRH8D58

8.3 × 8.3 × 6

25

3.3

10

Coilcraft

DS3316P

12.95 × 9.40 ×

80

3.5

5.08

10

Sumida

CDRH8D43

8.3 × 8.3 × 4.5

29

4

6.8

Würth Elektronik

74454068

12.7 × 10 × 4.9

55

4.1

To achieve high efficiency a Schottky type should be used for the rectifier diode. The reverse voltage rating

Usually a Schottky diode with 2 A maximum average rectified forward current rating is sufficient for most

applications. The Schottky rectifier can be selected with lower forward current capability depending on the output

current times the diode forward voltage.

Typically the diode should be able to dissipate around 500mW depending on the load current and forward

voltage.

Table 2. Rectifier Diode Selection

CURRENT

Vr

SUPPLIER

COMPONENT CODE

RATING Iavg

2 A

20 V

0.44 V / 2 A

Vishay Semiconductor

SL22

2 A

20 V

0.5 V / 2 A

Fairchild Semiconductor

SS22

10

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