LT3507

21

3507f

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

SW

GND

(12a)

C1

D1

C2

3507 F12

L1

SW

GND

(12c)

SW

GND

(12b)

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

this resistance can fall by another 25%. Further increases

in airflow will lead to lower thermal resistance.