SC621 datasheet(16/23 Pages) SEMTECH

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SC621

PCB Layout Considerations

The layout diagram in Figure 1 illustrates a proper

two-layer PCB layout for the SC621 and supporting

components.

Following fundamental layout rules is

critical for achieving the performance specified in the

Electrical Characteristics table. The following guidelines

are recommended when developing a PCB layout:

Place all bypass and decoupling capacitors —

C1, C2, CIN, COUT, CLDO1, CLDO2, and CBYP as

close to the device as possible.

All charge pump current passes through VIN,

VOUT, and the bucket capacitor connection

pins. Ensure that all connections to these pins

make use of wide traces so that the resistive

drop on each connection is minimized.

The thermal pad should be connected to the

ground plane using multiple vias to ensure

proper thermal connection for optimal heat

transfer.

•

Applications Information (continued)

Make all ground connections to a solid

ground plane as shown in the example layout

(Figure 3).

If a ground layer is not feasible, the following

groupings should be connected:

PGND — CIN, COUT

AGND — Ground Pad, CLDO1, CLDO2,

CBYP

If no ground plane is available, PGND and

AGND should be routed back to the negative

battery terminal as separate signals using thick

traces. Joining the two ground returns at the

terminal prevents large pulsed return currents

from mixing with the low-noise return currents

of the LDOs.

Both LDO output traces should be made as

wide as possible to minimize resistive losses.

•

COUT

CIN

CBYP

CLDO2

BL1

BL2

LDO1

LDO2

BYP

C2-

SWIF

SC621

GND

CLDO1

GND

PGND

Figure 1 — Recommended PCB Layout

Figure 2 — Layer 1

Figure 3 — Layer 2

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