Rainbow Electronics MAX8884Z - Manual (Page 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 A ) is the temperature difference
between the MAX8884Y/MAX8884Z die junction and
the surrounding air, and
θ
JA 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.
P
T T
MAX
J MAX A
JA
=
−
( )
_
θ
B3
A1 A2 A3 A4
B1 B2 B4
C1 C2 C3 C4
D1 D3 D4
BUCK LDO1
4.0mm
3.8mm
LDO2
IN
GND
SEL
D2
LDO2_EN BUCK_EN LDO1_EN
PGND
LX
IN1A
FB NC2
IN1B
LDO1_EN LDO1
IN2
LDO2 BUCK_EN
SEL
LDO2_EN
NC1 AGND REFBP
C
REFBP
C LDO2
C LDO1
C IN2
C IN1
L BUCK
C BUCK
Figure 1. Recommended PCB Layout