Datasheet
LTM8052/LTM8052A
20
8052fc
For more information www.linear.com/LTM8052
applicaTions inForMaTion
No Output Current Sharing
The LTM8052/LTM8052A is a two quadrant device, able to
both sink and source current to maintain voltage regulation.
It is therefore not suitable for current sharing.
PCB Layout
Most of the headaches associated with PCB layout have
been alleviated or even eliminated by the high level of
integration of the LTM8052/LTM8052A. The LTM8052/
LTM8052A 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 6 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
ADJ
and R
T
resistors as close as possible to
their respective pins.
2. Place the C
IN
capacitor as close as possible to the V
IN
and GND connection of the LTM8052/LTM8052A.
CTL_T
CTL_I
V
REF
COMP
SS
ADJ
SYNC
V
IN
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V
IN
8052 F06
GND
GND
C
IN
V
OUT
V
OUT
C
OUT
GND
THERMAL AND INTERCONNECT VIAS
RUN
RT
• •
3. Place the C
OUT
capacitor as close as possible to the
V
OUT
and GND connection of the LTM8052/LTM8052A.
4. Place the C
IN
and C
OUT
capacitors such that their
ground currents flow directly adjacent or underneath
the LTM8052/LTM8052A.
5. Connect all of the GND connections to as large a copper
pour or plane area as possible on the top layer. Avoid
breaking the ground connection between the external
components and the LTM8052/LTM8052A.
6. Use vias to connect the GND copper 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 printed circuit
board. Pay attention to the location and density of the
thermal vias in Figure 6. The LTM8052/LTM8052A can
benefit from the heat sinking afforded by vias that con
-
nect 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.
Figure 6. Layout Showing Suggested External Components,
GND Plane and Thermal Vias