YB1509
High-Power White LED Driver
and going through the I
SET
resistor to
ground. The higher the I
SET
pin voltage, the
larger the peak inductor current is built up.
application, such as for battery-powered
application.
Choosing inductor with low ESR decrease
power losses and increase efficiency.
Diode selection
To maintain high efficiency, the average
current rating of the schottky diode should
be large than the peak inductor current.
Schottky diode with a low forward drop and
fast switching speeds are ideal for increase
efficiency in portable application. Choose a
reverse breakdown of the schottky diode
large than the output voltage.
Thermal Consideration:
When YB1509 is set to handle high switch
current will result in internal power
dissipation and thus generating heat.
Always beware the amount of power
dissipated during operation. To resolve the
thermal built up issue, reduce resistance at
I
SET
which lower the peak switch current.
Layout consideration
The input capacitor C
IN
must be placed
close to the IC. This will reduce copper
trace resistance which effect input voltage
ripple of the IC. The output capacitor, C
OUT
,
should also be placed close to the IC. Any
copper trace connections for the C
OUT
capacitor can increase the series
resistance, which directly effect output
voltage ripple. The feedback resister
should be kept close to the FB pin to
minimize copper trace connections that can
inject noise into the system. The ground
Application Information
Enable/Shutdown
The YB1509 comes with an active-high
enable pin that allows the white LED driver
to be enabled. Forcing the enable pin low
disables the chip and puts it into the
shutdown mode. This pin cannot be left
floating; as it may cause an undetermined
state.
Input/Output Capacitor
It is recommended to use a 10µF capacitor
on the YB1509 input and a 4.7µF capacitor
on the output. Higher capacitance is
allowed to reduce the voltage and current
ripple. Choose low ESR capacitors for the
output to minimize output ripple. Multilayer
ceramic capacitors are good choice for the
input and output capacitor.
Inductor
The appropriate inductor for a given
application is calculated using the following
equation:
⎛
V
−
V
IN,MIN
+
V
D
L
= ⎜
OUT
⎜
I
SET
⎝
⎞
⎟
T
OFF
⎟
⎠
Where VD is the schottky diode voltage,
I
SET
is the setting for inductor current, and
T
OFF
is the switch off time designed for 1µs.
When using this equation be sure to use
the minimum input voltage for the
YB1509 MRev.1.1
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YOBON [ YOBON TECHNOLOGIES,INC. ]
