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YB1509 データシート(PDF) 6 Page - YOBON TECHNOLOGIES,INC. |
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YB1509 データシート(HTML) 6 Page - YOBON TECHNOLOGIES,INC. |
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6 / 7 page  YB1509 High-Power White LED Driver YB1509 MRev.1.1 www.yobon.com.tw 6 and going through the ISET resistor to ground. The higher the ISET pin voltage, the larger the peak inductor current is built up. 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: OFF SET D MIN IN, OUT T I V V V L ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ + − = Where VD is the schottky diode voltage, ISET is the setting for inductor current, and TOFF is the switch off time designed for 1µs. When using this equation be sure to use the minimum input voltage for the 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 ISET which lower the peak switch current. Layout consideration The input capacitor CIN must be placed close to the IC. This will reduce copper trace resistance which effect input voltage ripple of the IC. The output capacitor, COUT, should also be placed close to the IC. Any copper trace connections for the COUT 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 |
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