LM2675 datasheet(20/30 Pages) TI

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LM2675

SNVS129E – MAY 2004 – REVISED JUNE 2005

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APPLICATION INFORMATION

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

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)

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 29. PC Board Layout

Layout is very important in switching regulator designs. Rapidly 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 22 and Figure 23) 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

inductor. Allowing the inductor flux to intersect sensitive feedback, IC ground path, and COUT wiring can cause

problems.

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