EUP2538
Inductor Selection
The recommended value of inductor for 2 to 10 WLEDs
applications are 4.7µH to 47µH. Small size and better
efficiency are the major concerns for portable device,
such as EUP2538 used for mobile phone. The inductor
should have low core loss at 1MHz and low DCR for
better efficiency. To avoid inductor saturation current
rating should be considered.
Schottky Diode Selection
The current rating of the Schottky diode must exceed the
peak current flowing through it. The Schottky diode
performance is rated in terms of its forward voltage at a
given current. In order to achieve the best efficiency, this
forward voltage should be as low as possible. The
response time is also critical since the driver is operating
at 1MHz.
Board Layout
Careful PC board layout is required due to fast switching.
All components must be placed as close to the device as
possible. Keep the path between the inductor L1, diode D1,
and output capacitor COUT extremely short for minimal
noise and ringing. The feedback components such as the
sense resistor RFB must be kept close to the FB pin to
prevent noise injection on the FB pin trace. The ground
return of CIN and COUT should be tied close to the GND pin.
See the EUP2538 demo board layout for reference.
DS2538 Ver1.3 Nov. 2008
10
EUTECH [ EUTECH MICROELECTRONICS INC ]
