Component selection guidelines

AN3352

12/26

Doc ID 018526 Rev 3

2.1

DC-DC converter inductor (L1)

The LNBH24L operates with a standard 22 µH inductor for the entire range of supply

voltages and load current. The inductor saturation current rating (where inductance is

approximately 70% of zero current inductance) must be greater than the switch peak current

–

–

–

In this condition the switch peak current is calculated using the formula in Equation 1:

Equation 1

where:

–

Eff is the efficiency of the DC-DC converter (93% typ. at highest load)

–

L is the inductance (22 µH typ.)

–

F is the PWM frequency (220 kHz typ.)

Example:

Application conditions:

Index

Quantity

Reference

Value / generic part number

Package

11

2

C3A, C3B

220 µF > 25 V ESR = 50 m

Ω − 350 mΩ (see

El.Al. Radial

12

2

L1A, L1B

13

2

D1A, D2B

14

2

D2A, D2B

15

2

D3A, D3B

S1A or equivalent

SMB

16

2

D4A, D4B

BAT54, STPS130A, BAT43, 1N5818, or similar

SOD123

17

1

IC1

To be placed as close as possible to EXTM pin

QFN32

18

2

TR1A, TR1B

BC817

SOT23-3L

19

2

D8A, D8B

LL4148

MINIMELF

20

3

CN3, CN6, CN7

Strip 4p M

HDR1X4

21

9

CN1, CN4, CN5,

JP1-A, JP1-B, JP2-A,

JP2-B, LNBOUT-A,

LNBOUT-B

Strip 2p M

HDR1X2

Table 4.

LNBH24L demonstration board BOM list (continued)

⎟

⎠

⎞

⎜

⎝

⎛ −

+

=

ma x

mi n

1

2

mi n

mi n

*

ma x

ma x *

VU P

VI N

LF

VI N

VI N

Ef f

IO U T

VU P

Ip e a k