LM2671 datasheet(22/26 Pages) NSC

22 / 26 page

Application Information

TYPICAL SURFACE MOUNT PC BOARD LAYOUT,

FIXED OUTPUT (4X SIZE)

10004239

CIN - 15 µF, 25V, Solid Tantalum Sprague, “594D series”

COUT - 68 µF, 10V, Solid Tantalum Sprague, “594D series”

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

L1 - 47 µH, L13, Coilcraft DO3308

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.

10004240

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 - 100 µH, L20, Coilcraft DO3316

CB - 0.01 µF, 50V, Ceramic

R1 - 1k, 1%

R2 - Use formula in Design Procedure

FIGURE 18. PC Board Layout

LM2671 Datasheet(PDF) 22 Page - National Semiconductor (TI)