SNVS129E – MAY 2004 – REVISED JUNE 2005
APPLICATION INFORMATION
TYPICAL SURFACE MOUNT PC BOARD LAYOUT, FIXED OUTPUT (4X SIZE)
C
IN
- 15
μF,
50V, Solid Tantalum Sprague, “594D series”
C
OUT
- 68
μF,
16V, Solid Tantalum Sprague, “594D series”
D1 - 1A, 40V Schottky Rectifier, Surface Mount
L1 - 33
μH,
L23, Coilcraft DO3316
C
B
- 0.01
μF,
50V, Ceramic
TYPICAL SURFACE MOUNT PC BOARD LAYOUT, ADJUSTABLE OUTPUT (4X SIZE)
C
IN
- 15
μF,
50V, Solid Tantalum Sprague, “594D series”
C
OUT
- 33
μF,
25V, Solid Tantalum Sprague, “594D series”
D1 - 1A, 40V Schottky Rectifier, Surface Mount
L1 - 68
μH,
L30, Coilcraft DO3316
C
B
- 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
and
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 C
OUT
wiring can cause
problems.
20
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