yb1522 YOBON TECHNOLOGIES,INC., yb1522 Datasheet - Page 11

• Manufacturer Part Number: yb1522
• Description: Step-up Dc-dc Converter White Led Driver
• Manufacturer: YOBON TECHNOLOGIES,INC.

Over Voltage Protection
The YB1522 has an internal over voltage
protection circuit which also acts as an
open-circuit protection. In the cases of
open circuit or the LEDs failure, the LEDs
are disconnected from the circuit, and the
feedback voltage will be zero. The YB1522
will then switch to a high duty cycle
resulting in a high output voltage, which
may cause SW pin voltage to exceed its
maximum 30V rating. The YB1522 will
shutdown automatically until input condition
changes to bring it out of the shutdown
mode.
Inductor Selection
A 33uH inductor is recommended for most
applications to drive more than 3x7 WLEDs.
Although small size and high efficiency are
major concerns, the inductor should have
low core losses at 1MHz and low DCR
(copper wire resistance).
Diode Selection
To maintain high efficiency, the average
current rating of the Schottky diode should
be large than the peak inductor current, I
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.
Capacitor Selection
Choose low ESR capacitors for the output
to minimize output voltage ripple. Multilayer
capacitors are a good choice for this as well.
A 10uF capacitor is sufficient for 3x7
WLEDs
bypassing, a 100nF ceramic capacitor can
YB1522 Rev.1.0
applications.
Step-up DC-DC Converter White LED Driver
For
additional
www.yobon.com.tw
PK
.
be used to shunt high frequency ripple on
the input.
The input bypass capacitor C
in Figure 1, must be placed close to the IC.
This will reduce copper trace resistance
which affects input voltage ripple of the IC.
For additional input voltage filtering, a
100nF bypass capacitor can be placed in
parallel with C
frequency noise to ground. The output
capacitor, C
close
connections for the C
increase the series resistance, which
directly effect output voltage ripple.
The feedback network, resister R2 should
be kept close to the FB pin to minimize
copper trace connections that can inject
noise
connection
network should connect directly to an
analog ground plane. The analog ground
plane should tie directly to the GND pin. If
no analog ground plane is available, the
ground
network should tie directly to the GND pin.
Trace connections made to the inductor
and Schottky diode should be minimized to
reduce power dissipation and increase
overall efficiency.
to
into
connection
the
OUT
for
the
, should also be placed
IN
IC.
the
system.
to shunt any high
Any
for
OUT
feedback
YB1522
the
capacitor can
copper
The
IN
, as shown
feedback
resistor
ground
trace
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