EUP3408
PC Board Layout Checklist
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:
When laying out the printed circuit board, the following
guidelines should be used to ensure proper operation of
the EUP3408.
1. The input capacitor CIN should connect to VIN 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 VIN trace should be kept short,
direct and wide.
TR=(PD)(θJA)
2
Where PD=ILOAD × RDS(ON) is the power dissipated by
3. The VFB pin should connect directly to the feedback
resistors. The resistive divider R1/R2 must be
connected between the COUT and ground.
the regulator ; θJA is the thermal resistance from the
junction of the die to the ambient temperature.
The junction temperature, TJ, is given by:
4. Keep the switching node, SW, away from the
sensitive VFB node.
TJ=TA+TR
Where TA is the ambient temperature.
TJ should be below the maximum junction temperature
of 125°C.
DS3408 Ver1.2 Nov. 2007
9
EUTECH [ EUTECH MICROELECTRONICS INC ]
