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| YB1509 High-Power White LED Driver Description The YB1509 is a high-power boost converter. An adjustable current limit, wide range of input voltage, and up to 40V of switch voltage are designed to drive white LEDs back-lighting for large LCD panel. It can drive up to 10 LEDs in series or 18 LEDs in parallel/series configuration. The wide application VIN range makes YB1509 suitable for many types of battery applications such as Li-ions, Alkaline, or Sealed Lead Acid batteries. The adjustable inductor current optimizes the performance for different output drive capability by an external resistor. The LED current is set by a resistor connected to FB pin. The On/Of duty with clock frequency from 1K to 100KHz at EN pin can control the LED brightness Features 2V to 16V Input Voltage 40V Maximum Output Voltage Drive up to 18 White LEDs Adjustable Inductor Current 1s Constant Off-time PFM Control 1KHz to 100KHz PWM Dimming Control Applications PDA, Palmtops and Smart Phones LCD Monitor LCD TV Portable DVD player White LED backlighting GPS navigation system Handheld Game Typical Application Circuit VIN= 6 to14V 10uF 16V 22uH SL12 VIN 4.7uF 35V EN Bypass Iset LX YB1509 FB BZV55-B 36 2KOHM 10nF 6.3V GND 1K RFB 60OHM Figure 1. Typical application circuit YB1509 MRev.1.1 www.yobon.com.tw 1 YB1509 High-Power White LED Driver Pin Configuration G ND 1 8 LX VIN 2 7 Iset YB 1509 B ypass 3 6 NC FB 4 5 EN M SO P8 Figure 2. Pin configuration Pin Description Table 1 Pin 1 2 3 4 5 6 7 8 Name GND VIN Bypass FB EN NC ISET LX Signal and power ground. Input supply pin. Description Internal compensation usage. A 10nF bypass capacitor is recommended. Feedback input pin. Enable control input. Active high. No connect. Set inductor current. Switch pin, connect to external inductor. Ordering Information Order Number YB1509 Package Type MSOP-8 Supplied as 2500 units Tape & Reel Package Marking YB1509 YB1509 MRev.1.1 www.yobon.com.tw 2 YB1509 High-Power White LED Driver Absolute Maximum Ratings Supply Voltage......................................... -0.3V to 16V LX Switch Voltage.................................... -0.3V to 40V Junction Temperature Range........................... +150 Storage Temperature Range ............. -65 to +150 Recommended Operating Conditions Input Supply Voltage.............................. 2.2V to 16V Operating Temperature..................... -40 to +85 Lead Temperature............................................ +250 Electrical Characteristics At TA=25 Table 2 , VIN=6V, unless otherwise noted. Function Parameter Input Voltage Range VFB Threshold Voltage VFB Pin Bias Current Quiescent Current Quiescent Current in shutdown Switching Off Time Switching On VCE,SAT LX Leakage Current EN Logic Low Level EN Logic High Level EN Input Bias Current EN Input Bias Current ISET Source Current Inductor Peak Current ISWITCH=300mA VFB=1.23V Conditions Min 2.2 1.21 180 Typ Max 16 Units V V nA A A s 1.23 1.25 250 400 10 VFB=1.5V, not switching VEN=0V 1 220 1 330 10 0.4 mV A V V A A A A VFB=1.5V, VLX=40V EN pin voltage low EN pin voltage high VEN=3V VEN=0V 6 Rlimit=15K, Vin=12V, Vout=30V, Iout = 150mA 1.4 1.8 VIN 4.5 15 1 8 1.5 10 1.6 YB1509 MRev.1.1 www.yobon.com.tw 3 YB1509 High-Power White LED Driver Typical Characteristics . VIN=3 to 6V 10F 16V VIN EN Bypass 33H SL12 VIN=5 to 8V 10F 16V 22H SL12 4.7F 35V LX EN Bypass VIN LX 4.7F 35V YB1509 FB YB1509 FB ISET 10nF 9.1K GND ISET RFB 60OHM 10nF 1K GND RFB 60OHM Figure 3. 8 LEDs in a Series Figure 4. 10 LEDs in a Series 33H VIN=8 to 14V VIN=8 to 14V 10F 16V VIN EN Bypass LX 4.7F 35V 10H SL12 SL12 10F 16V VIN EN Bypass LX 4.7F 35V YB1509 FB YB1509 FB ISET 10nF 1K GND ISET RFB1 60OHM RFB2 60OHM 10nF 1K GND RFB1 60OHM RFB2 60OHM Figure 5. 2 Legs of 6 LEDs in a Series Figure 6. 2 Legs of 9 LEDs in a Series CH1: LX CH2: Inductor Current CH3: VOUT (18 LEDs) Figure 7. Typical Switching Waveform CH1: EN CH2: LX CH3: VOUT (18 LEDs) Figure 8. PWM Brightness Control by EN YB1509 MRev.1.1 www.yobon.com.tw 4 YB1509 High-Power White LED Driver Functional Block Diagram VBAT CIN L1 Charge Enable EN VIN SW Cout Bypass VFB 1.23V VREF D1 Set Q Reset O ff Tim e Control Q1 10nF ISET G ND 60O HM Figure 9. Block Diagram Functional Description The YB1509 is a constant current high-power white LED driver. It can drive up to 10 LEDs in series or 18 LEDs in parallel/series configuration. The IC uses a peak current, 1s off-time PFM scheme. The inductor current ramp up when power NPN is turn on. Once the inductor current reaches the preset value determined by the ISET pin, output power NPN is shut off and the energy stored in inductor is delivered to the output capacitor. Once the discharge cycle is completed, the power NPN is on again. If the FB voltage has not yet reached the designated value of 1.23V, the inductor current will be charged up again. This charging and discharging sequence will repeat itself until the FB voltage gets to the designated value and triggers the on-off YB1509 MRev.1.1 latch to hold off the power NPN regardless the inductor current value. LED Current and Brightness control The LED's current is set by the resistor connected at FB pin to GND using: I LED = 1.23V RFB LED's brightness is accomplished by applying a PWM signal with a frequency range between 100Hz and 50KHz to the EN pin. Inductor Current Set Using a resistor connected from ISET to GND is able to set inductor current. An 8A current source is coming out of the YB1509 5 www.yobon.com.tw YB1509 High-Power White LED Driver and going through the ISET resistor to ground. The higher the ISET pin voltage, the larger the peak inductor current is built up. 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 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 10F capacitor on the YB1509 input and a 4.7F 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: V - VIN,MIN + VD L = OUT I SET TOFF Where VD is the schottky diode voltage, ISET is the setting for inductor current, and TOFF is the switch off time designed for 1s. When using this equation be sure to use the minimum input voltage for the YB1509 MRev.1.1 www.yobon.com.tw 6 YB1509 High-Power White LED Driver connection for the feedback resistor network should connect directly to an analog ground plane. Trace connections made to the inductor and schottky diode should be short and wider for reducing power dissipation and increase overall efficiency. Package Information YB1509 MRev.1.1 www.yobon.com.tw 7 |
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