YB1303 Datasheet, PDF (6/8 Pages) YOBON TECHNOLOGIES,INC. – Low Dropout LED Driver

YB1303
Low Dropout LED Driver
Example 1:
Drive low V_F white or blue LEDs directly
from single cell Li-Ion battery
When using white or blue low V_F LEDs,
and utilizing the driver’s low voltage drop,
only 3.4V in V_IN is needed for the full 20mA
LED current. At 3.2V, there is still 5mA
typical current available for the LEDs. The
single cell Li-Ion battery is utilized in many
applications like cell-phones and digital still
cameras. In most cases, the Li-Ion battery
voltage level only goes down to 3V, and not
down to the full discharged level (2.7V)
before requesting the charger.
Example 2:
Drive high VF white or blue LEDs from
exiting bus from 4.0V to 6V
High V_F white or blue LEDs have forward
voltage drop in the range of 3.2V to 4.0V.
To drive these LEDs with the maximum
current of 20mA for maximum brightness,
usually requires a boost circuit for a single
cell Li-Ion voltage range. In some cases,
there is already a voltage bus in the system,
which can be utilized. Due to the ultra-low
voltage drop of the YB1303 to drive high V_F
white or blue LEDs, the V_IN needs to be
only 300mV higher than the highest V_F in
the circuit.
-V_DROP < 0.3V
-V_F (@20mA) < 3.1V (Low V_F)
-V_IN (@20mA) = -V_DROP+V_F=3.4V
-V_IN (@5mA typical) ~3.1V
Where V_IN = Single cell Li-Ion Voltage
Key advantages:
y No boost circuit needed for the LCD or
keyboard backlight.
y Drivers directly connected to a Li-Ion
battery.
y No EMI, no switching noise, no boost
efficiency lost, no capacitor and no
inductor.
-V_DROP < 0.3V
-V_F (@20mA) < 3.3V to 4.0V (High V_F)
-V_IN (@20mA) = -V_DROP+V_F=3.6V to 4.3V
-V_IN (@5mA typical) ~3.3V
Where V_IN = Existing bus = 3.3V to 4.3V
Key advantages:
y No boost circuit needed for the LCD or
keyboard backlight.
y Driver utilizes the existing bus.
y Ultra-low voltage drop provides the full
20mA LED current at the lowest possible
voltage level.
YB1303 Rev.1.0
www.yobon.com.tw
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