LM2614ATLX NSC [National Semiconductor], LM2614ATLX Datasheet - Page 15

• Manufacturer Part Number: LM2614ATLX
• Description: 400mA Sub-Miniature Adjustable DC-DC Converter Optimized for RF Power Amplifiers
• Manufacturer: NSC [National Semiconductor]

Application Information
3. Arrange the components so that the switching current
4. Connect the ground pins of the LM2614, and filter ca-
5. Use wide traces between the power components and for
loops curl in the same direction. During the first half of
each cycle, current flows from the input filter capacitor,
through the LM2614 and inductor to the output filter
capacitor and back through ground, forming a current
loop. In the second half of each cycle, current is pulled
up from ground, through the LM2614 by the inductor, to
the output filter capacitor and then back through ground,
forming a second current loop. Routing these loops so
the current curls in the same direction prevents mag-
netic field reversal between the two half-cycles and re-
duces radiated noise.
pacitors together using generous component-side cop-
per fill as a pseudo-ground plane. Then, connect this to
the ground-plane (if one is used) with several vias. This
reduces ground-plane noise by preventing the switching
currents from circulating through the ground plane. It
also reduces ground bounce at the LM2614 by giving it
a low-impedance ground connection.
power connections to the DC-DC converter circuit. This
(Continued)
15
6. Route noise sensitive traces, such as the voltage feed-
7. Place noise sensitive circuitry, such as radio IF blocks,
In mobile phones, for example, a common practice is to
place the DC-DC converter on one corner of the board,
arrange the CMOS digital circuitry around it (since this also
generates noise), and then place sensitive preamplifiers and
IF stages on the diagonally opposing corner. Often, the
sensitive circuitry is shielded with a metal pan and power to
it is post-regulated to reduce conducted noise, using
low-dropout linear regulators.
reduces voltage errors caused by resistive losses across
the traces.
back path, away from noisy traces between the power
components. The voltage feedback trace must remain
close to the LM2614 circuit and should be routed directly
from V
opposite to noise components. This reduces EMI radi-
ated onto the DC-DC converter’s own voltage feedback
trace.
away from the DC-DC converter, CMOS digital blocks
and
noise-sensitive circuitry in the system can be reduced
through distance.
OUT
other
at the output capacitor and should be routed
noisy
circuitry.
Interference
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