lm2672ldx-adj National Semiconductor Corporation, lm2672ldx-adj Datasheet - Page 21

• Manufacturer Part Number: lm2672ldx-adj
• Description: Simple Switcher Power Converter High Efficiency 1a Step-down Voltage Regulator With Features
• Manufacturer: National Semiconductor Corporation

Application Information
TYPICAL SURFACE MOUNT PC BOARD LAYOUT, FIXD OUTPUT (4X SIZE)
C
C
D1 - 1A, 40V Schottky Rectifier, Surface Mount
L1 - 33 μH, L23, Coilcraft DO3316
C
TYPICAL SURFACE MOUNT PC BOARD LAYOUT, ADJUSTABLE OUTPUT (4X SIZE)
C
C
D1 - 1A, 40V Schottky Rectifier, Surface Mount
L1 - 68 μH, L30, Coilcraft DO3316
C
R1 - 1k, 1%
R2 - Use formula in Design Procedure
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 2 and Figure 3) should be wide
printed circuit traces and should be kept as short as pos-
sible. For best results, external components should be locat-
ed as close to the switcher IC as possible using ground plane
construction or single point grounding.
IN
OUT
B
IN
OUT
B
- 0.01 μF, 50V, Ceramic
- 0.01 μF, 50V, Ceramic
- 15 μF, 50V, Solid Tantalum Sprague, “594D series”
- 15 μF, 50V, Solid Tantalum Sprague, “594D series”
- 68 μF, 16V, Solid Tantalum Sprague, “594D series”
- 33 μF, 25V, Solid Tantalum Sprague, “594D series”
FIGURE 18. PC Board Layout
21
If open core inductors are used, special care must be taken
as to the location and positioning of this type of inductor. Al-
lowing the inductor flux to intersect sensitive feedback, IC
ground path, and C
When using the adjustable version, special care must be tak-
en as to the location of the feedback resistors and the asso-
ciated wiring. Physically locate both resistors near the IC, and
route the wiring away from the inductor, especially an open
core type of inductor.
OUT
wiring can cause problems.
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1293439
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