SC419 datasheet(21/24 Pages) SEMTECH

21 / 24 page

SC419

Applications Information (continued)

Connect the V

OUT sense trace directly to

the output capacitor or a ceramic bypass

capacitor.

Route this trace over to the VOUT pin,

carefully avoiding all switching nets and

power components.

Route this trace in a quiet layer if possible.

Route this trace away from the switch-

ing traces and components, even if the

trace is longer. Avoid shorter trace routing

through the power switching area.

If a bypass capacitor is used at the IC side

of the trace, it should be placed near the

FB resistor divider.

All components connected to the FB pin must

be located near the pin. The FB traces should be

kept small and not routed near any noisy switch-

ing connections or power components.

Place the R

ILIM resistor near the IC. For an accu-

rate I

LIM current sense connection, route the RILIM

trace directly to the drain of the low-side MOSFET

(LX). Use an inner routing layer if needed.

Place the R

TON resistor near the TON pin. Route

this to the TON trace using a short trace and

avoid all switching signals.

Bypass Capacitors

The device requires bypass capacitors for the following

pins.

VDDA pin with respect to AGND. This 100nF

minimum capacitor must be placed and routed

close to the IC pins, on the same layer as the IC.

VDDP with respect to PGND. This 1μF minimum

capacitor must be placed and routed close to

the IC pins and on the same layer as the IC.

BST pin with respect to LX. This 100nF minimum

capacitor must be placed near the IC, on either

side of the PCB. Use short traces for the routing

between the capacitor and the IC.

VIN pin with respect to AGND. This 100nF

minimum capacitor must be placed and routed

close to the IC pins. This capacitor provides

noise filtering for the input to the internal on-

time circuit.



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