EUP3408
Thermal Considerations
To avoid the EUP3408 from exceeding the maximum
junction temperature, the user will need to do a thermal
analysis. The goal of the thermal analysis is to determine
whether the operating conditions exceed the maximum
junction temperature of the part. The temperature rise is
given by:
T
R
=(P
D
)(θ
JA
)
Where P
D
=I
LOAD2
×
R
DS(ON)
is the power dissipated by
the regulator ;
θ
JA
is the thermal resistance from the
junction of the die to the ambient temperature.
The junction temperature, T
J
, is given by:
T
J
=T
A
+T
R
Where T
A
is the ambient temperature.
T
J
should be below the maximum junction temperature
of 125°C.
PC Board Layout Checklist
When laying out the printed circuit board, the following
guidelines should be used to ensure proper operation of
the EUP3408.
1. The input capacitor C
IN
should connect to V
IN
as
closely as possible. This capacitor provides the AC
current to the internal power MOSFETs.
2. The power traces, consisting of the GND trace, the
SW trace and the V
IN
trace should be kept short,
direct and wide.
3. The V
FB
pin should connect directly to the feedback
resistors. The resistive divider R1/R2 must be
connected between the C
OUT
and ground.
4. Keep the switching node, SW, away from the
sensitive V
FB
node.
DS3408 Ver1.2
Nov. 2007
9
EUTECH [ EUTECH MICROELECTRONICS INC ]
