SC4525AEVB View Datasheet(PDF) - Semtech Corporation

Part Name

Description

MFG CO.

SC4525AEVB

28V 3A Step-Down Switching Regulator

Semtech Corporation 

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 IN

VOUT

ZL

Figure 9. Heavy lines indicate the critical pulse

current loop. The inductance of this

loop should be minimized.

SC4525A

Vin

Curre nts in Power Section

15

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