BL8331 Non-isolated Buck Off Offline LED Driver Features Description The BL8331 is a high precision buck k constant current LED driver. It is suitable for 85Vac~ ~265Vac universal low power offline LED lighting. The BL8331 integrates a 500V power er MOSFET. It doesn’t need the auxiliary windiing for supplying the chip. It can achieve excellent constant current performance with very few exterrnal components, so the system cost and size are miniimized. The BL8331 utilizes patent pending ng current control method. It can achieve ± 3% LED ED output current acccuracy The output current does oes not change with the inductance and LED output voltage. age. Internal 500V Power M MOSFET ± 3% LED Output Curreent Accuracy Ultra Low Operating ng Cu Current No Auxiliary Winding Critical Conduction Mode Operation LED Short Protection Available in SOP-8 Pack ackage Applications LED Candle Light LED Bulb Other LED Lighting The BL8331 offers rich protection functions func to improve the system reliability, includ uding LED open circuit protection, LED short circuit protection, VCC under voltage protection, CS resisstor short circuit protection and thermal regulation func unction. Typical Application BL8331 Datasheet V1.0 1 BL8331 Non-isolated Buck Off Offline LED Driver ORDERING INFORMATION Device Package BL8333S SOP8 Shipping Rail/2500pcs Mark PIN ASSIGNMENT and DESCRIPTION PIN NO SYMBOL 1 2 3 4 5,6 7,8 GND RADJ NC VDD DRN ISEN DESCRIPTION Ground Over Voltage Protection SettingPin.Connect n.Connect a resistor. No Connection. Power Supply Pin. Internal MOSFET Drain. Current Sense Pin.Connect a resistor sistor between this pin and GND. Absolute Maximum Ratin ngs (note1) Symbol Parameters Range Units VDD Power Supply -0.3~20 V Vdrn Drain Voltage -0.3~500 500 V CS Current sense pin input i voltage -0.3~6 V 5 IDDMAX Maximum sink curr rrent VRADNJ Over-voltage setting ng pin p voltage -0.3~6 V Power dissipation 450 mW θJA Thermal resistance ance (Junction to Ambient) 145 ℃/W TJ Operating junction on temperature -40 too 150 ℃ TSTG Storage temperaturre range -55 too 150 ℃ 2000 V PDMAX ESD ESD mV Note 1: Stresses beyond those listed under “absol olute maximum ratings” may cause permanent damage to the device. BL8331 Datasheet V1.0 2 BL8331 Non-isolated Buck Off Offline LED Driver Recommended Operation n Conditions Symbol Para Parameter Range Unit ILED1 Input put LED current Voltage 155@ VOUT =80V mA ILED2 Input LED ED current Voltage 255@ VOUT =36V mA VMIN Minimum LED L Loading Voltage >15 V Electrical Characteristics Symbol VDD_CLP IDD VST Parameter er VCC Clamp Vo oltage VCC Operating Current C VCC Turn On Th hreshold VCC Startup Cu urrent IST VUVLO VCC Turn off Threshold Thre Current Sense Section Threshold Voltage for VISEN Peak Current Lim mit Threshold Voltage age for VISEN-SHT Peak Current Limiit When TLEB TDELAY MOSFET Section BVDSS RSW VRADJ Range 15.8~17.2 Units V ≤135 135 12.8~14.2 2.8~14.2 VDD= VST - 1V ≤195 195 8.1~9.1 uA V uA V 392~408 mV 198 mV 500 ns 150 ns VGS=0V/IDS=250uA 500 V VGS=15V/IDS=0.4A 16 Ω VGS=0V/VDS=500V 0.5 uA 0.55 55 45 255 55 5 V us us us 155 ℃ VCC Falling Output Short Output Shorrt Leading Edge Blanking B Time for Current ent Sense Switch Off Delay ay Time Drain-Source Breakdo akdown Voltage Static Drain-source source Onresistance Power MOSFET ET Drain Leakage eakage Current Internal Time Control Section IDSS Conditions 0.8mA FSYS=65KHz VCC Rising ROVP Pin Voltage age Maximum ON Time T Maximum OFF Time TOFF_MAX Minimum OFF Time TOFF_MIN Thermal Regulation Section TREG Thermal Regulation Temperature TON_MAX BL8331 Datasheet V1.0 3 BL8331 Non-isolated Buck Off Offline LED Driver Application Information The BL8331 is a high performance non-isolated non Buck converter specially designed for LED LE lighting. The device integrates a 500V power MOS SFET. It achieves excellent line regulation lation and load regulation.with regulation.w very MOSFET can be calculated bby the equation: = 400 ; = × − few external components Where, I P is peak currentt of the inductor, L is the inductance value, VIN is the he DC bus voltage after the rectifier bridge,VLED is the vvoltage on the LED. Start Up After the power MOSFET ET is switched off, the current in the inductor decre reases. When the inductor After system powered up, the VDD DD pin capacitor is charged up by the start up resistor. When the VDD pin voltage reaches the turn on thresshold, the internal circuits start operating. Due to the ultra-low operating curreent, the auxiliary winding is not needed to supply the IC. C. Constant Current Control The BL8331 works under CRM mode with a internal 400mV reference voltage and the voltage age on CS pin is compared with the peak inductor current ent The peak inductor current is given by: = 400 2 current reaches zero, the power MOSFET is turned on again by IC internal llogic. The off time of the MOSFET is given by: = × The inductance can be calcu culated by the equation: = × ( × − × ) The F is the system swittching frequency, which is proportional to the input nput voltage. So the minimum switching frequency is seet at lowest input voltage, and the maximum switching ng frequency is set at highest input voltage. The minimum and maximuum off time of BL8331 is set at 50KHZ and 120KHZ, resspectively. Referring to the Where, ILED is driving current, RISEN is the current sense resistor value. Inductor Selection The BL8331 works under CRM mode. m When the power MOFET is switched on, the he current cu in the inductor rises up from zero, the on time of the BL8331 Datasheet V1.0 4 BL8331 Non-isolated Buck Off Offline LED Driver small, the tOFF may be smaller than the he minimum off time, system will operate in n discontinuous conduction mode and the output current cu will be smaller than the designed value. If the he inductance is too large, the tOFF may be larger than han the maximum off time, the system will operate in continuous conduction mode and the output current cu will be higher than the designed value. So itt is important to choose a proper inductance. Over Voltage Protection When the LED is open circuit, the he output voltage increases gradually, and the demagne agnetization time gets shorter. The over voltage pro otection can be programmed by the RADJ resistor ≈ × × 15 × 10 ( ohm) × Where, V is the ISEN turn off threshold (400mV) L is the inductance value RISEN is the current sense resistor value. ue. Vovp is the open circuit protection voltage. voltage Protection Function The BL8331 offers rich protection on functions to improve the system reliability, including LED open/short protection, ISEN resistor short protection, VDD under/over voltage protection, the hermal regulation. When the LED is open circuit, the t system will trigger the over voltage protec ection and stop switching. When the LED short circuit is detec ected, the system works at low frequency (5kHz), So the he system power consumption is very low. At some so catastrophic fault condition, such as ISEN resisstor shorted or inductor saturated, the internal fastt fault detection circuit will be triggered, the system m stops s switching immediately. BL8331 Datasheet V1.0 After the system enters intoo fault condition, the VCC voltage will decrease unti til it reaches the UVLO threshold, then the system will re-start again. If the fault condition is removed, tthe system will recover to normal operation. The BL8331 integrates thermal regulation function. When the system is over temperature, the output current is gradually reduced; th the output power and thermal dissipation are also reduced. The system temperature is regulated and the system reliability is improved. The thermal regulation temperature is set to 155℃ internally. PCB Layout The following rules should be followed in BL8331 PCB layout: The bypass capacitor on VDD pin should be as close as possible to the VDD Pin and GN GND pin. The area of main current loop should be as small as possible to reduce EMI radiation, such as the inductor, the power MOSFET, the output diode and the bus capacitor loop. The power ground path for current sense should be short, and the power ground path should be separated from small signal ground path before connecting to the negative node of the bulk capacitor. The RADJ resistor should bee as close as possible to the RADJ Pin. The NC pin should be conneccted to GND (pin1). To increase the copper area of DRAIN pin for better thermal dissipation. However too large copper area may compromise EMI performance. 5 BL8331 Non-isolated Buck Off Offline LED Driver PACKAGE OUTLINE BL8331: SOP8 L E E1 ? TYPICAL MAX A 1.350 1.10 1.750 A1 0.100 --- 0.250 A2 1.350 1.10 1.550 b 0.330 0.40 0.510 c 0.170 0.125 0.250 D 4.700 2.90 5.100 E 3.800 1.60 4.000 E1 5.800 e --- 1.90(typ) --- L 0.400 --- 1.270 θ 0° 5° 8° 6.200 A A2 A1 e BL8331 Datasheet V1.0 MIN c D b SIZE（ （mm） SYMBOL 6