Rainbow-electronics MAX8884Z Instrukcja Użytkownika Pobierz pdf (Strona 13)

MAX8884Y/MAX8884Z

700mA DC-DC Step-Down Converters

with Dual 300mA LDO in 2mm x 2mm CSP

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The maximum allowed power dissipation, P

MAX

, is:

where (T

JMAX

- T

) is the temperature difference

between the MAX8884Y/MAX8884Z die junction and

the surrounding air, and θ

is the thermal resistance of

the junction through the PCB, copper traces, and other

materials to the surrounding air.

PCB Layout

High switching frequencies and relatively large peak

currents make the PCB layout a very important part of

design. Good design minimizes excessive EMI on the

feedback paths and voltage gradients in the ground

plane, resulting in a stable and well regulated output.

Minimize the ground loop formed by C

IN1

, C

BUCK

, and

PGND. To do this, connect C

IN1

close to IN1A/IN1B

and PGND. Connect the inductor and output capacitor

as close as possible to the IC and keep their traces

short, direct, and wide. Keep noisy traces, such as the

LX node, as short as possible. Connect AGND and

PGND to the common ground plane. Figure 1 illustrates

an example PCB layout and routing scheme.

MAX

J MAX A

−

()

A1 A2 A3 A4

B1 B2 B4

C1 C2 C3 C4

D1 D3 D4

BUCK

LDO1

4.0mm

3.8mm

LDO2

GND

SEL

LDO2_EN

BUCK_EN

LDO1_EN

PGND

IN1A

FBNC2

IN1B

LDO1_ENLDO1

IN2

LDO2 BUCK_EN

SEL

LDO2_EN

NC1AGND

REFBP

LDO2

LDO1

IN2

IN1

BUCK

Figure 1. Recommended PCB Layout

1 2 ... 8 9 10 11 12 13 14 15

MAX8884Y/MAX8884Z 1

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