Datasheet

LT3507
21
3507fa
Figure 12. Subtracting the Current When the Switch is ON (12a) From the Current When the Switch is OFF (12b) Reveals the Path of
the High Frequency Switching Current (12c) Keep this Loop Small. The Voltage on the SW and Boost Nodes Will Also be Switched;
Keep These Nodes as Small as Possible. Finally, Make Sure the Circuit is Shielded with a Local Ground Plane
APPLICATIONS INFORMATION
Figure 13. Power Path Components and Topside Layout
V
IN
SW
GND
(12a)
V
IN
V
SW
C1 D1 C2
3507 F12
L1
SW
GND
(12c)
V
IN
SW
GND
(12b)
I
C1
THERMAL CONSIDERATIONS
The high output current capability of the LT3507 will require
careful attention to power dissipation of all the components
to insure a safe thermal design. The PCB must provide
heat sinking to keep the LT3507 cool. The Exposed Pad on
the bottom of the package must be soldered to a ground
plane. This ground should be tied to other copper layers
below with thermal vias; these layers will spread the heat
dissipated by the LT3507. Place additional vias near the
catch diodes. Adding more copper to the top and bottom
layers and tying this copper to the internal planes with vias
can reduce thermal resistance further. With these steps, the
thermal resistance from die (or junction) to ambient can be
reduced to θ
JA
= 34°C/W or less. With 100 LFPM airfl ow,
this resistance can fall by another 25%. Further increases
in airfl ow will lead to lower thermal resistance.