ISL854102DEMO2Z datasheet(18/21 Pages) RENESAS

18 / 21 page

ISL854102

FN8870 Rev.1.00

Page 18 of 21

Mar 15, 2019

Layout Considerations

Proper layout of the power converter minimizes EMI and noise,

and ensures first pass success of the design. Printed Circuit

Board (PCB) layouts are provided in multiple formats on the

Renesas website. In addition, Figure 39 illustrates the important

points in PCB layout. In reality, PCB layout of the ISL854102 is

quite simple.

A multilayer PCB with GND plane is recommended. Figure 39

shows the connections of the critical components in the

converter. Note that capacitors CIN and COUT can each represent

multiple physical capacitors. The most critical connections are to

tie the PGND pin to the package GND pad and then use vias to

directly connect the GND pad to the system GND plane. This

connection of the GND pad to system plane ensures a low

impedance path for all return current and an excellent thermal

path to dissipate heat. With this connection made, place the high

frequency MLCC input capacitor near the VIN pin and use vias

directly at the capacitor pad to tie the capacitor to the system

GND plane.

The boot capacitor is easily placed on the PCB side opposite the

controller IC and two vias directly connect the capacitor to BOOT

and PHASE.

Place a 1µF MLCC near the VCC pin and directly connect its

return with a via to the system GND plane.

Place the feedback divider close to the FB pin and do not route

any feedback components near PHASE or BOOT. If external

components are used for SS, COMP, or FS, the same advice

applies.

FIGURE 38. SIMULATED LOOP GAIN

-15

-30

100

10k

100k

FREQUENCY (Hz)

180

150

120

100

10k

100k

FREQUENCY (Hz)

COUT

CVIN

CSS

RFS

FIGURE 39. PRINTED CIRCUIT BOARD POWER PLANES AND ISLANDS

RFS

CSS

CVIN

COUT

0.47”

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