LTC3544 datasheet(13/16 Pages) LINER

13 / 16 page

LTC3544

3544fa

PC Board Layout Checklist

When laying out the printed circuit board, the following

checklist should be used to ensure proper operation of

the LTC3544. These items are also illustrated graphically

in Figures 3 and 4. Check the following in your layout:

1. The power traces, consisting of the PGND trace, the

GNDA trace, the SW traces, the PVIN trace and the VCC

trace should be kept short, direct and wide.

2. Does each of the VFBx pins connect directly to the

respective feedback resistors? The resistive dividers

must be connected between the (+) plate of the corre-

sponding output ﬁlter capacitor (e.g., C13) and GNDA.

If the circuit being powered is at such a distance from

the part where voltage drops along circuit traces are

large, consider a Kelvin connection from the powered

circuit back to the resistive dividers.

APPLICATIONS INFORMATION

3. Keep C8 and C9 as close to the part as possible.

4. Keep the switching nodes (SWx) away from the sensi-

tive VFBx nodes.

5. Keep the ground connected plates of the input and

output capacitors as close as possible.

6. Care should be taken to provide enough space between

unshielded inductors in order to minimize any trans-

former coupling.

Design Example

As a design example, consider using the LTC3544 as a

portable application with a Li-Ion battery. The battery

provides VIN ranging from 2.8V to 4.2V. The demand at

2.5V is 250mA necessitating the use of the 300mA output

for this requirement.

VOUT3

C12

R11

C10

VOUT2

VOUT4

3544 F03

SW200B

SW300

PGND

PVIN

SW1000

RUN100

GNDA

C15

R15

R16

RUN100

VFB100

RUN200A

SW200A

VFB200B

VFB200A

VFB200B

VFB300

RUN300

RUN200B

VFB200A

VCC GNDA

PGND

VCC

2.25V TO 5.5V

PVIN

2.25V TO 5.5V

LTC3544

C13

VOUT1

Figure 3. LTC3544 Layout Diagram

Figure 4. LTC3544 Suggested Layout

C10

GND

PGND

3544 F04

VCC

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