SNVS124C – NOVEMBER 1999 – REVISED APRIL 2013
Test Circuit and Layout Guidelines
Fixed Output Voltage Versions
C
IN
—470
μF,
50V, Aluminum Electrolytic Nichicon “PL Series”
C
OUT
—220
μF,
25V Aluminum Electrolytic, Nichicon “PL Series”
D1 —5A, 40V Schottky Rectifier, 1N5825
L1 —68
μH,
L38
Adjustable Output Voltage Versions
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
—220
μF,
35V Aluminum Electrolytic, Nichicon “PL Series”
D1 —5A, 40V Schottky Rectifier, 1N5825
L1 —68
μH,
L38
R1 —1 kΩ, 1%
C
FF
—See
Section
Figure 20. Standard Test Circuits and Layout Guides
As in any switching regulator, layout is very important. 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 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
inductor. 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
section for more information.)
Copyright © 1999–2013, Texas Instruments Incorporated
Product Folder Links:
9
TI [ TEXAS INSTRUMENTS ]
