AN3352 datasheet(13/26 Pages) STMICROELECTRONICS

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AN3352

Component selection guidelines

Doc ID 018526 Rev 3

13/26

VUPmax = VOUTmax + VDROP = 19.2 V + 0.75 V = 19.95 V

IOUTmax = 500 mA

Eff = 90% (worst-case in these conditions)

Based on Equation 1 and the preceding application conditions, IPEAK is:

Equation 2

Then, in this example, an inductor with saturation current > 1.52 A should be recommended.

Several inductors suitable for the LNBH24L are listed in Table 5, although there are many

other manufacturers and devices that can be used. Consult each manufacturer for more

detailed information and for their entire selection of related parts, as many different shapes

and sizes are available. Ferrite core inductors should be used to obtain the best efficiency.

Choose an inductor that can handle at least the IPEAK current without saturating, and ensure

that the inductor has a low DCR (copper wire resistance) to minimize power losses and,

consequently, to maximize the total efficiency.

2.2

Output current limit selection (R2-RSEL)

The linear regulator current limit threshold can be set through an external resistor connected

to the ISEL pin. The resistor value defines the typical output current threshold limit by the

equation:

Equation 3

220

Ipeak

⎟

⎠

⎞

⎜

⎝

⎛ −

∗

−

Table 5.

Recommended Inductors

Vendor

Part number

ISAT (A)

DRC (m?)

Mounting type

Sumida

CD104-220MC

RHC110-220M

1.6

2.4

SMD

Through-hole

Toko

822LY-220K

824LY-220K

A671HN-220L

A814LY-220M

1.3

1.72

2.44

2.0

Through-hole

SMD

Panasonic

ELC08D220E

ELC10D220E

1.8

3.2

Through-hole

Coilcraft

DC1012-223

PVC-0-223-03

DO3316P-223

2.5

2.6

Through-hole

SMD

Rsel

10000

)

(

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