LM2671N-5.0 National Semiconductor, LM2671N-5.0 Datasheet - Page 20

• Manufacturer Part Number: LM2671N-5.0
• Description: DC/DC Converter IC
• Manufacturer: National Semiconductor

Specifications of LM2671N-5.0

• Input Voltage: 40V
• Output Current: 500mA
• Output Voltage: 5V
• No. Of Pins: 8
• Mounting Type: Through Hole
• Voltage Regulator Type: Buck Switching
• Output Current Max: 0.5A
• Peak Reflow Compatible (260 C): No
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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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
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
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”
OUT
wiring can cause problems.
FIGURE 18. PC Board Layout
20
When using the adjustable version, special care must be
taken as to the location of the feedback resistors and the as-
sociated wiring. Physically locate both resistors near the IC,
and route the wiring away from the inductor, especially an
open core type of inductor.
DS100042-39
DS100042-40