Datasheet
LT3507
22
3507fb
For more information www.linear.com/LT3507
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
PCB LAYOUT
For proper operation and minimum EMI, care must be
taken during printed circuit board (PCB) layout. Figure 12
shows the high current paths in the step-down regula-
tor circuit. Note that in the step-down regulators large,
switched currents flow in the power switch, the catch
diode and the input capacitor. The loop formed by these
components should be as small as possible. Place these
components, along with the inductor and output capacitor
,
on the same side of the circuit board and connect them
on that layer. Place a local, unbroken ground plane below
these components and tie this ground plane to system
ground at one location, ideally at the ground terminal of
the output capacitor C2. Additionally, keep the SW and
BOOST nodes as small as possible. Figure 13 shows an
example of proper PCB layout.
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