LM2596
Test Circuit and Layout Guidelines
(Continued)
Adjustable Output Voltage Versions
01258323
where V
REF
= 1.23V
Select R
1
to be approximately 1 kΩ, use a 1% resistor for best stability.
C
IN
— 470 µF, 50V, Aluminum Electrolytic Nichicon “PL Series”
C
OUT
D1
L1
R1
C
FF
— 220 µF, 35V Aluminum Electrolytic, Nichicon “PL Series”
— 5A, 40V Schottky Rectifier, 1N5825
— 68 µH, L38
— 1 kΩ, 1%
— See Application Information Section
FIGURE 1. Standard Test Circuits and Layout Guides
As in any switching regulator, layout is very important. 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 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 lC 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,
lC groundpath and C
OUT
wiring can cause problems.
When using the adjustable version, special care must be
taken as to the location of the feedback resistors and the
associated wiring. Physically locate both resistors near the
IC, and route the wiring away from the inductor, especially an
open core type of inductor. (See application section for more
information.)
9
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