ltm8033 Linear Technology Corporation, ltm8033 Datasheet - Page 16

• Manufacturer Part Number: ltm8033
• Description: Ultralow Noise Emc 36vin, 3a Dc/dc
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
LTM8033
PCB Layout
Most of the headaches associated with PCB layout have
been alleviated or even eliminated by the high level of
integration of the LTM8033. The LTM8033 is neverthe-
less a switching power supply, and care must be taken to
minimize EMI and ensure proper operation. Even with the
high level of integration, you may fail to achieve specified
operation with a haphazard or poor layout. See Figure 4
for a suggested layout. Ensure that the grounding and
heat sinking are acceptable.
A few rules to keep in mind are:
1. Place the R
2. Place the C
3. Place the C
16
their respective pins.
to the V
A haphazardly placed C
performance.
V
OUT
and GND connection of the LTM8033.
IN
, FIN and GND connections of the LTM8033.
ADJ
IN
OUT
and C
and R
capacitors as close as possible to the
FIN
T
resistors as close as possible to
capacitors as close as possible
FIN
R
ADJ
R
T
capacitor may impair EMI
GND
SHARE
Figure 4. Layout Showing Suggested External
Components, GND Plane and Thermal Vias
THERMAL VIAS TO GND
PG
V
SYNC
OUT
C
OUT
GND
GND
4. Place the C
5. Connect all of the GND connections to as large a copper
6. Use vias to connect the GND copper area to the board’s
ground currents flow directly adjacent or underneath
the LTM8033.
pour or plane area as possible on the top layer. Avoid
breaking the ground connection between the external
components and the LTM8033.
internal ground planes. Liberally distribute these GND
vias to provide both a good ground connection and
thermal path to the internal planes of the printed circuit
board. Pay attention to the location and density of the
thermal vias in Figure 4. The LTM8033 can benefit from
the heat sinking afforded by vias that connect to internal
GND planes at these locations, due to their proximity
to internal power handling components. The optimum
number of thermal vias depends upon the printed
circuit board design. For example, a board might use
very small via holes. It should employ more thermal
vias than a board that uses larger holes.
RUN/SS
BIAS
AUX
C
IN
LTM8033
IN
V
IN
, C
FIN
FIN
and C
C
FIN
OUT
capacitors such that their
8033f