YB1509 High-Power White LED Driver Description Features 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. 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 PWM Dimming Control 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. Applications PDA, Palmtops and Smart Phones LCD Monitor LCD TV Portable DVD player The LED current is set by a resistor White LED backlighting connected to FB pin. The On/Of duty with clock frequency from 1K to 100KHz at EN pin can control the LED brightness GPS navigation system Handheld Game Typical Application Circuit VIN= 6 to14V 10uF 16V 22uH SL12 VIN 4.7uF 35V LX EN Bypass YB1509 Iset 10nF 6.3V BZV55-B 36 FB 2KOHM RFB 60OHM GND 1K 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 Name Description 1 GND Signal and power ground. 2 VIN Input supply pin. 3 Bypass 4 FB Feedback input pin. 5 EN Enable control input. Active high. 6 NC No connect. 7 ISET Set inductor current. 8 LX Switch pin, connect to external inductor. Internal compensation usage. A 10nF bypass capacitor is recommended. Ordering Information Order Number Package Type Supplied as Package Marking YB1509 MSOP-8 2500 units Tape & Reel YB1509 YB1509 MRev.1.1 www.yobon.com.tw 2 YB1509 High-Power White LED Driver Absolute Maximum Ratings Recommended Operating Conditions Supply Voltage......................................... -0.3V to 16V Input Supply Voltage.............................. 2.2V to 16V LX Switch Voltage.................................... -0.3V to 40V Operating Temperature..................... -40℃ to +85℃ Junction Temperature Range........................... +150℃ Storage Temperature Range ............. -65℃ to +150℃ Lead Temperature............................................ +250℃ Electrical Characteristics At TA=25℃, VIN=6V, unless otherwise noted. Table 2 Function Parameter Conditions Min Input Voltage Range 2.2 VFB Threshold Voltage 1.21 Typ 1.23 180 Max Units 16 V 1.25 V 250 nA VFB Pin Bias Current VFB=1.23V Quiescent Current VFB=1.5V, not switching 400 µA Quiescent Current in shutdown VEN=0V 10 µA Switching Off Time 1 Switching On VCE,SAT ISWITCH=300mA LX Leakage Current VFB=1.5V, VLX=40V EN Logic Low Level EN pin voltage low EN Logic High Level EN pin voltage high EN Input Bias Current VEN=3V EN Input Bias Current VEN=0V Inductor Peak Current YB1509 MRev.1.1 220 330 mV 1 10 µA 0.4 V VIN V 15 µA 1 µA 1.8 4.5 ISET Source Current Rlimit=15K, Vin=12V, Vout=30V, Iout = 150mA www.yobon.com.tw µs 6 8 10 µA 1.4 1.5 1.6 A 3 YB1509 High-Power White LED Driver Typical Characteristics . 33µH VIN=3 to 6V SL12 22µH VIN=5 to 8V 10µF 16V SL12 10µF 16V 4.7µF 35V VIN LX EN YB1509 Bypass 4.7µF 35V VIN LX EN Bypass FB YB1509 FB ISET ISET 10nF RFB 60OHM GND 9.1K 10nF Figure 3. 8 LEDs in a Series Figure 4. 10 LEDs in a Series 33µH VIN=8 to 14V 10µH VIN=8 to 14V SL12 4.7µF 35V VIN 4.7µF 35V VIN Bypass YB1509 RFB1 60OHM 10nF YB1509 ISET FB ISET LX EN LX EN 1K SL12 10µF 16V 10µF 16V Bypass RFB 60OHM GND 1K RFB2 60OHM FB 10nF GND 1K GND RFB1 60OHM Figure 6. 2 Legs of 9 LEDs in a Series Figure 5. 2 Legs of 6 LEDs in a Series CH1: LX CH2: Inductor Current CH3: VOUT (18 LEDs) Figure 7. Typical Switching Waveform YB1509 MRev.1.1 RFB2 60OHM CH1: EN CH2: LX CH3: VOUT (18 LEDs) Figure 8. PWM Brightness Control by EN www.yobon.com.tw 4 YB1509 High-Power White LED Driver Functional Block Diagram VBAT CIN L1 D1 Charge Enable EN SW VIN Cout Bypass 10nF 1.23V VREF Set Q VFB Reset O ff Tim e Control Q1 I SET 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, 1µs 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 8µA current source is coming out of the YB1509 www.yobon.com.tw 5 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 Information 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 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: 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. 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 Inductor The appropriate inductor for a given application is calculated using the following equation: ⎞ ⎟⎟ TOFF ⎠ 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 YB1509 MRev.1.1 Choosing inductor with low ESR decrease power losses and increase efficiency. Diode selection Enable/Shutdown ⎛ V − VIN,MIN + VD L = ⎜⎜ OUT I SET ⎝ application, such as for battery-powered application. 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 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