LM2672 datasheet(21/25 Pages) NSC

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Application Information

TYPICAL SURFACE MOUNT PC BOARD LAYOUT, FIXD OUTPUT (4X SIZE)

01293439

CIN - 15 µF, 50V, Solid Tantalum Sprague, “594D series”

COUT - 68 µF, 16V, Solid Tantalum Sprague, “594D series”

D1 - 1A, 40V Schottky Rectifier, Surface Mount

L1 - 33 µH, L23, Coilcraft DO3316

CB - 0.01 µF, 50V, Ceramic

TYPICAL SURFACE MOUNT PC BOARD LAYOUT, ADJUSTABLE OUTPUT (4X SIZE)

Layout is very important in switching regulator designs. Rap-

idly switching currents associated with wiring inductance can

generate voltage transients which can cause problems. For

minimal inductance and ground loops, the wires indicated by

heavy lines (in

Figure 2 and Figure 3) should be wide

printed circuit traces and should be kept as short as

possible. For best results, external components should be

located as close to the switcher IC as possible using ground

plane construction or single point grounding.

If open core inductors are used, special care must be

taken as to the location and positioning of this type of induc-

tor. Allowing the inductor flux to intersect sensitive feedback,

IC ground path, and C

OUT wiring can cause problems.

When using the adjustable version, special care must be

taken as to the location of the feedback resistors and the

associated wiring. Physically locate both resistors near the

IC, and route the wiring away from the inductor, especially an

open core type of inductor.

01293440

CIN - 15 µF, 50V, Solid Tantalum Sprague, “594D series”

COUT - 33 µF, 25V, Solid Tantalum Sprague, “594D series”

D1 - 1A, 40V Schottky Rectifier, Surface Mount

L1 - 68 µH, L30, Coilcraft DO3316

CB - 0.01 µF, 50V, Ceramic

R1 - 1k, 1%

R2 - Use formula in Design Procedure

FIGURE 18. PC Board Layout

LM2672 数据表(PDF) 21 Page - National Semiconductor (TI)

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