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Número de pieza | YB1508 | |
Descripción | Step-up DC-DC Converter | |
Fabricantes | YOBON TECHNOLOGIES | |
Logotipo | ||
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YB1508
Step-up DC-DC Converter , White LED Driver
Description
Features
The YB1508 is a step-up DC-DC converter,
acting as current source to drive up to 8
white LEDs in series. Series connecting of
the LEDs provides identical LED currents
resulting in uniform brightness and
eliminating the need for ballast resistors.
The light intensity of these LEDs is
proportional to the current passing through
them. Additional features include output over
voltage protection to prevent device damage
due to faulty LED or open circuit caused by
abnormal conditions, and one-pin shutdown
and multiple methods of dimming control.
The YB1508 switches at a fixed frequency of
1MHz, allowing the use of tiny external
components and low input noise and ripple.
To control LED brightness, the LED current
can be pulsed by applying a PWM (pulse
width modulated) signal with a frequency
range of 100Hz to 50KHz to the CTRL pin.
The YB1508 is available in a low profile 5-lead
SOT-23 package.
Typical Application Circuit
2.7V to 9V input range
Adjustable output voltage up to 40V
Built in internal switch
Inherently matched LED current
Fixed frequency of 1MHz PWM
operation
Open LED protection
Low profile 5-Lead SOT-23 package
High efficiency: over 80% at 3.6V
input voltage
Drives up to 8 white LEDs
Applications
LCD Display Module
OLED panel/sub-panel
White LED Backlighting
Digital Camera
Cellular Phone
Portable Application
YB1508 MRev1.4
Figure 1:Typical Application Circuit
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YB1508
Step-up DC-DC Converter , White LED Driver
Inrush Current
The maximum switch current is limited to
about 300 mA by the chip. Typically, this
large current will occur for about 40us
during start up. A larger Cout will increase
the duration of high current. However,
when Vin is first connected, an even
larger current can flow into Cout. This
occurs when the SW pin is open circuit
and and the Cout voltage changes from
0V to Vin in a few microseconds. Because
the duration of this large current is short, it
will usually not cause problems.
LED Current and Dimming Control
The LED current can be reduced by pulse
width modulating the CTRL voltage from
0.4V to 1.8V. Using the PWM mode, the
LED current can be controlled from 0% to
100%.
Open Circuit Protection
The YB1508 has an internal open-circuit
protection circuit. When the LEDs are
disconnected from the circuit or fail
open, the YB1508 will then shutdown
until Vin goes low or CTRL goes lower
than 0.4V. Different maximum Vout
can be requested from YoBon.
Board Layout Consideration
To maximize efficiency, rise and fall
times of switch should be made as
short as possible. Proper layout of the
high frequency switching path is
important to prevent electromagnetic
interference (EMI) problems. Place
COUT close to the VOUT pin. A
ground plane under the switching
regulator is needed to minimize
interplane coupling. In addition, the
feedback resistor Rs should be tied
directly to the GND Pin without any
other connection to ensure a clean,
noise-free connection.
Figure 4. Dimming Control Using a DC Voltage
Figure 5. Dimming Control Using a Filtered PWM
Signal
YB1508 MRev1.4
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5 Page |
Páginas | Total 7 Páginas | |
PDF Descargar | [ Datasheet YB1508.PDF ] |
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