SC4524FEVB datasheet(17/23 Pages) SEMTECH

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SC4524F

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,thesizeoftheloopformedbythesecomponents

should be minimized. Since the power switch is already

integrated within the SC4524F, 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 large vias directly under the device.

O UT

Figure 9 — Pulse current Loop

Note: Heavy lines indicate the critical pulse current loop. The stray

inductance of this loop should be minimized

SC4524FEVB Datasheet(PDF) 17 Page - Semtech Corporation