Description YB1519 is a high power boost converter. An adjustable current limit, wide range of input voltages, and switching voltages up to 40V are designed to drive white LED backlights for large LCD panels. It can drive up to 10 LEDs in series or 18 LEDs in parallel/series. The wide range of applications makes the YB1519 suitable for many types of battery applications such as Li-ion, Alkaline or sealed lead-acid batteries. Adjustable inductor current through an external resistor optimizes performance for different output drive capabilities. The LED current is set by a resistor connected to the FB pin. Typical application circuit characteristics of en-pin with clock frequency of 1k~100khz that can control LED brightness on/off work
2V to 16V Input Voltage 40V Maximum Output Voltage Drive Up to 18 White LEDs Adjustable Inductor Current 1μs Constant Off Time pfm Control 1kHz to 100kHz Pulse Width Modulation Dimming Control Applications High Power WLED Backlight Solutions LCD Display LCD TV Car TV, Portable DVD GPS Navigation System

Typical features

Functional block diagram

Functional Description YB1519 is a constant current high power white LED driver. It can drive up to 10 LEDs in series or 18 LEDs in parallel/series. The IC adopts a peak current, 1μs off-time pfm scheme. When the power npn is turned on, the inductor current rises. Once the inductor current reaches a preset value determined by the ISET pin, the output power NPN is cut off and the energy stored in the inductor is transferred to the output capacitor. After the discharge cycle is complete, the power supply NPN is turned on again. If the fb voltage has not reached the specified value of 1.23v, the inductor current will charge again. This charge-discharge sequence is repeated until the FB voltage reaches the specified value and triggers the switch latch to hold the power npn regardless of the inductor current value. LED Current and Brightness Control The LED current is set by a resistor connected between the FB pin and GND, using:
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The brightness of the LED is achieved by applying a pulse width modulated signal with a frequency range of 100Hz to 50KHz to the EN pin.

Use from ISET to
YB1519 High Power White LED Driver
GND can set the inductor current. An 8µA current source comes out of the YB1519 and is grounded through the ISET resistor. The higher the ISET pin voltage, the larger the inductor current peak.
Application Information Enable/Disable The YB1519 has 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 shutdown mode. This pin cannot be left floating; as it may lead to an undetermined state. Input/Output Capacitor It is recommended to use a 10μF capacitor at the YB1519 input and a 4.7μF capacitor at the output. Higher capacitance reduces voltage and current ripple. Choose low ESR capacitors for the output to minimize output ripple. Multilayer ceramic capacitors are ideal for input and output capacitors. Inductors The appropriate inductor for a given application is calculated using the following formula:

off where vd is the Schottky diode voltage, iset is the inductor current setting, and toff is the off-time designed for 1µs

Minimize copper trace connections that could inject noise into the system. The ground connection of the feedback resistor network should be connected directly to the analog ground plane. Trace connection pair inductors and Schottky diodes should be made short and wide to reduce power dissipation and improve overall efficiency

When using this formula, be sure to use the minimum input voltage, such as in battery-powered applications. Choosing a low esr inductor can reduce power dissipation and improve efficiency. Diode selection To maintain high efficiency, the average current rating of the Schottky diode should be greater than the peak current of the inductor. With low forward voltage drop and fast switching speed, Schottky diodes are ideal for increasing efficiency in portable applications. Choose a Schottky diode with reverse breakdown greater than the output voltage. Thermal Considerations: When the YB1519 is set up to handle high switching currents, internal power dissipation results in heat generation. During operation, be sure to pay attention to the power consumed. To address the heat build-up problem, reduce the resistance at ISET, thereby reducing the peak switch current. Layout Considerations The input capacitor cin must be close to ic. This will reduce the copper trace resistance that affects the IC's input voltage ripple. The output capacitor cout should also be close to ic. Any copper wire connection to the cout capacitor will increase the series resistance and directly affect the output voltage ripple.