SC4525A Semtech Corporation, SC4525A Datasheet - Page 15

• Manufacturer Part Number: SC4525A
• Description: 28V 3A Step-Down Switching Regulator
• Manufacturer: Semtech Corporation

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Applications Information (Cont.)
PCB Layout Considerations
In a step-down switching regulator, the input bypass
capacitor, the main power switch and the freewheeling
diode carry pulse current (Figure 9). For jitter-free
operation, the size of the loop formed by these components
should be minimized. Since the power switch is already
integrated within the SC4525A, connecting the anode of
the freewheeling diode close to the negative terminal of
the input bypass capacitor minimizes size of the switched
current loop. The input bypass capacitor should be placed
close to the IN pin. Shortening the traces of the SW and
BST nodes reduces the parasitic trace inductance at these
nodes. This not only reduces EMI but also decreases
switching voltage spikes at these nodes.
The exposed pad should be soldered to a large ground
plane as the ground copper acts as a heat sink for the
device. To ensure proper adhesion to the ground plane,
avoid using vias directly under the device.
V
V
Figure 9. Heavy lines indicate the critical pulse
IN
IN
current loop. The inductance of this
loop should be minimized.
Vin
Vin
Z
Z
L
L
V
V
OUT
OUT
Curre nts in Power Section
Curre nts in Power Section
SC4525A
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