AN2713 datasheet(12/40 Pages) STMICROELECTRONICS

12 / 40 page

Component selection guidelines

AN2713

12/40

Doc ID 14431 Rev 1

3.1

Input capacitors

An electrolytic bypass capacitor (C1 in Figure 5) between 100 µF and 470 µF located close

to the LNBH23 is needed for stable operation. In any case, a ceramic capacitor between 100

nF and 470 nF is recommended to reduce the switching noise at the input voltage pin.

3.2

Ferrite bead

The most important parameter when selecting the ferrite bead is the rated current. Ensure

that the ferrite has a current rating of at least 2 A and impedance higher than 60

Ω at 100

MHz.

3.3

DC-DC converter output capacitors

Two low-cost electrolytic capacitors are needed on the DC-DC converter output stage (C3

and C5 in Figure 5). Moreover, two ceramic capacitors are recommended to reduce high

frequency switching noise. The switching noise is due to the voltage spikes of the fast

switching action of the output switch, and to the parasitic inductance of the output

capacitors. To minimize these voltage spikes, special low-inductance ceramic capacitors

can be used, and their lead lengths must be kept short and as close as possible to the IC

pins (C4 and C6 in Figure 5). To further reduce switching noise, a ferrite bead is

recommended between the capacitors (see Section 3.2 for required rating and impedance).

C8, C10,

C11

0.22 µF 35 V ceramic capacitors

C12

0.01 µF 35 V ceramic capacitor

100

Ω 1/4 W resistor

R2 (RSEL)11 kΩ 1/16 W resistor (see Section 3.6)

10 k

Ω 1/4 W resistor

STPS130A or similar Schottky diode (see Section 3.4)

D2, D4

BAT43 BAT43 (or Schottky diode with IF(AV)>0.2 A, VRRM>25 V) or BAT30, BAT54, TMM BAT43,

1N5818

1N4007

22 µH Inductor with Isat>IPEAK (see Section 3.5)

Ferrite bead filter; recommended part numbers: Panasonic EXCELS A35, Murata BL01RN1-A62 or

equivalent with similar or higher impedance and current rating higher than 2 A (see Section 3.2)

220 µH inductor with current rating higher than rated output current

TVS

LNBTVS22-XX TVS protection diode is recommended. Other solutions can be used depending on

the level of surge protection required (see Section 3.9)

Table 2.

LNBH23 demonstration board BOM list (continued)

Component

Notes

AN2713 Datasheet(PDF) 12 Page - STMicroelectronics

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