Analog Devices LINEAR LTM 8005 Manual page 18

LTM8005
APPLICATIONS INFORMATION
5. Connect all of the GND connections to as large a cop-
per pour or plane area as possible on the top layer.
Avoid breaking the ground connection between the
external components and the LTM8005.
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 con-
nection and thermal path to the internal planes of the
printed circuit board. Pay attention to the location and
TO LED STRING
CATHODE (BOOST)
C
LED
Figure 10. Layout Showing Suggested External Components, GND Plane and Thermal Vias for a Buck-Boost Mode Application
18
GND
V
OUT
SW
V
IN
For more information
density of the thermal vias in Figures 9 and 10. The
LTM8005 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.
TO LED
STRING
(OPTIONAL
DIODE)
C
OUT
GND
ISN LED
IVINN IVINP
OVLO
V EN/UVLO
IN
C
IN
GND/THERMAL VIAS
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GND
RAMP
PWM
CTRL2
V
CTRL1
REF
RT
SS
VC
FB
AUX
GND
GND
8005 F10
Rev. B