ltm8062 Linear Technology Corporation, ltm8062 Datasheet - Page 15

• Manufacturer Part Number: ltm8062
• Description: Ltm8062 32vin, 2a ?module Power Tracking Battery Charger Features
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
PCB Layout
Most of the headaches associated with PCB layout have
been alleviated or even eliminated by the high level of
LTM8062 integration. The LTM8062 is nevertheless
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 7
for a suggested layout. Ensure that the grounding and
heat sinking are acceptable.
1. Place the C
2. If used, place the C
3. Place the C
4. Connect all of the GND connections to as large a copper
5. For good heat sinking, use vias to connect the GND cop-
and GND connection of the LTM8062.
to the BAT and GND connection of the LTM8062.
ground current flows directly adjacent or underneath
the LTM8062.
pour or plane area as possible on the top layer. Avoid
breaking the ground connection between the external
components and the LTM8062.
per area to the board’s internal ground planes. Liberally
distribute these GND vias to provide both a good ground
connection and thermal path to the internal planes of the
IN
IN
and C
capacitor as close as possible to the V
BAT
BAT
(if used) capacitors such that their
capacitor as close as possible
(OPTIONAL)
THERMAL VIAS
C
BAT
BAT
Figure 7. Suggested Layout and Via Placement
GND
IN
Hot-Plugging Safely
The small size, robustness and low impedance of ceramic
capacitors make them an attractive option for the input
bypass capacitor of LTM8062. However, these capacitors
can cause problems if the LTM8062 is plugged into a
live input supply (see Application Note 88 for a complete
discussion). The low loss ceramic capacitor combined
with stray inductance in series with the power source
forms an underdamped tank circuit, and the voltage at the
V
nominal input voltage, possibly exceeding the LTM8062’s
rating and damage the part. If the input supply is poorly
controlled or the user will be plugging the LTM8062 into
an energized supply, the input network should be designed
to prevent this overshoot. This can be accomplished by
installing a small resistor in series with V
popular method of controlling input voltage overshoot is
IN
printed circuit board. Pay attention to the location and
density of the thermal vias in Figure 5. The LTM8062
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.
ADJ
pin of the LTM8062 can ring to more than twice the
C
IN
RUN V
V
IN
INREG
GND
V
INA
8062 F07
LTM8062
IN
, but the most
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