LM2671LD-12 NSC [National Semiconductor], LM2671LD-12 Datasheet - Page 22

• Manufacturer Part Number: LM2671LD-12
• Description: SIMPLE SWITCHER Power Converter High Efficiency 500mA Step-Down Voltage Regulator with Features
• Manufacturer: NSC [National Semiconductor]

www.national.com
Application Information
TYPICAL SURFACE MOUNT PC BOARD LAYOUT,
FIXED OUTPUT (4X SIZE)
C
C
D1 - 1A, 40V Schottky Rectifier, Surface Mount
L1 - 47 µH, L13, Coilcraft DO3308
C
TYPICAL SURFACE MOUNT PC BOARD LAYOUT,
ADJUSTABLE OUTPUT (4X SIZE)
C
C
D1 - 1A, 40V Schottky Rectifier, Surface Mount
L1 - 100 µH, L20, Coilcraft DO3316
C
R1 - 1k, 1%
R2 - Use formula in Design Procedure
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
IN
OUT
B
IN
OUT
B
- 0.01 µF, 50V, Ceramic
- 0.01 µF, 50V, Ceramic
- 15 µF, 25V, Solid Tantalum Sprague, “594D series”
- 15 µF, 50V, Solid Tantalum Sprague, “594D series”
- 68 µF, 10V, Solid Tantalum Sprague, “594D series”
- 33 µF, 25V, Solid Tantalum Sprague, “594D series”
FIGURE 18. PC Board Layout
22
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.
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