eup3412 Eutech Microelectronics Inc, eup3412 Datasheet - Page 9

• Manufacturer Part Number: eup3412
• Description: 1.5a/1.5mhz, Synchronous Step-down Converter With Soft Start
• Manufacturer: Eutech Microelectronics Inc

Output Voltage Programming
The output voltage is set by a resistive divider according
to the following formula:
Choose R1 value 50kΩ for most applications.
The external resistive divider is connected to the output,
allowing remote voltage sensing as shown below.
Thermal Considerations
To avoid the EUP3412 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:
Where P
the regulator ; θ
junction of the die to the ambient temperature.
The junction temperature, T
Where T
T
of 125°C.
DS3412 Ver1.3 Mar. 2009
J
should be below the maximum junction temperature
T
T
A
R
J
D
=T
=(P
=I
is the ambient temperature.
LOAD
A
D
+T
)(θ
R
V
2
JA
JA
OUT
× R
)
is the thermal resistance from the
DS(ON)
=
0.5V
J
, is given by:
is the power dissipated by



1
+
R2
R1



9
PC Board Layout Checklist
For all switching power supplies, the layout is an
important step in the design especially at high peak
currents and switching frequencies. If the layout is not
carefully done, the regulator might show stability
problems as well as EMI problems.
When laying out the printed circuit board, the following
guidelines should be used to ensure proper operation of
the EUP3412.
1. The input capacitor C
2. The power traces, consisting of the GND trace, the
3. The FB pin should connect directly to the feedback
4. Keep the switching node, SW, away from the
closely as possible. This capacitor provides the AC
current to the internal power MOSFETs.
SW trace and the VIN trace should be kept short,
direct and wide.
resistors. The resistive divider R1/R2 must be
connected between the C
sensitive FB node.
IN
OUT
should connect to VIN as
EUP3412
and ground.