BL8532B White LED PFM Step-Up DC-DC Converter Outline: Features: • • • • • The BL8532B is a PFM Step-up DC/DC driver IC with invariant current, design for LED applications. Thought the external resistance, output current reach 0mA~500mA. A low ripple, high efficiency step-up DC/DC converter can be constructed of BL8532Bxx with only three external components. Also available is a CE (chip enable) function that reduce power consumption Low start voltage：0.8V ( at Iout=1mA)； Output Current range：0~ 500mA； Output Current accuracy：±10%； High Efficiency：82%(Type)； PACKAGE： SOT-89-5. Applications： • • • Power source for white LED Supply constant current Power source for a single or dual-cell battery-powered equipments ： Selection guide： ： Pin configuration： BL8532B-XX X XX □□PSN BL8532BPackage: SN：SOT-89-5 Temperature range: C：standard P：standard （Pb free） Feedback voltage: 10……100mV 20……200mV 25……250mV 30……300mV 35……350mV 40……400mV http://www.belling.com.cn Pin No. Symbol 1 IFB 2 Vout 3 CE 4 Lx 5 GND - 1Total 13 Pages Description Current feedback pin Output pin, power supply for internal circuits Chip enable pin (active high) Switching pin(Nch open drain) Ground pin 2/20/2013 BL8532B Functional block diagram ： Absolute maximum ratings: PARAMETER VIN Input Voltage Lx Pin voltage CE Pin voltage IFB output voltage Lx Pin current Continuous SOT-23-5 Total Power Dissipation SOT-89-5 Maximum Operating Ambient Temperature Operating Ambient Temperature Storage Temperature Soldering temperature and time SYMBAL VIN VLX VCE VIFB ILX RATINGS 0.3~9 0.3~Vout+0.3 0.3~Vout+0.3 0.3~Vout+0.3 1.5 UNITS V V V V mA Pd 300 mW Pd 500 mW Tmax 150 ℃ TOpr Tstg Tsolder -20~+85 -40~+125 260℃, 10s ℃ ℃ Recommended operating conditions: Input voltage range inductor Input capacitor Output capacitor* Operating junction temperature http://www.belling.com.cn MIN 0.8 10 0 47 -20 NOM 15 ≥22 100 - 2Total 13 Pages MAX Vout 100 220 85 UNIT V µH µF µF ℃ 2/20/2013 BL8532B Electrical characteristics: (Vin＝2.5V， VCE=Vout＝3.3V，R＝33Ω，TA=25°C, unless otherwise noted.) Symbol Item Test conditions Min Typ. Max Unit VOUT feedback Voltage IOUT=100mA 90 180 100 200 110 220 mV Vstart Starup Voltage 0.8 0.9 Vhold holding Voltage IDD2 Supply Current ILX ILXleak Ileak Fosc Lx Switching Current Lx Leakage Current CE is “L”, Leakage Current of the chip Oscillation Frequency IOUT=1mA, VIN：0→2V IOUT=1mA, VIN：2→0V LX empty, VCE=VIFB=VOUT=3.3 V VLX=0.4V, VIFB=0 0.6 0.9 V 36 µA 700 mA VOUT=VLX=VIFB=6V VOUT=3.3V, VCE=0, LX, IFB empty <0.1 VIFB=0 300 Maxdty Duty Ratio On(VLX“L”)side η Efficiency IOUT=250mA VCEH CE is “H”,input voltage VCEL CE is “L”,input voltage IOM Maximum output diver power VCE：0→2V (up to work slowly with the chip) VCE：0→2V (down to work off slowly with the chip) VIFB =0, VOUT =3.3V 77 0.6 V 79 1 µA 0.5 µA kHz 82 % 82 % 0.9 V 0.3 500 0.6 V mA Note: 1、 Diode：Schottky diode（forward voltage drop ： 0.3V，0.3A ），such as IN5817 or 1N5819 2、 Inductor：15μH（R<0.5Ω） 3、 Capacitor：100μF （Tantalum type ） 4、 VIFB (SET) is feedback voltage of the chip set up , is the first parameter of the table ,such as 100mV、200mV and so on。 http://www.belling.com.cn - 3Total 13 Pages 2/20/2013 BL8532B Typical applications: Constant output current application (A) Drive only one white LED (B) Drive two white-LED in series and several in parallel connection Suggestions: 1. you can increase the output capacitor properly for improve to the characteristic of the output invariant current ( for example：150uF or 200uF). 2. to avoid the feedback voltage excursion, please wear the ring with static electricity and the electric iron connect to ground when the soldering http://www.belling.com.cn - 4Total 13 Pages 2/20/2013 BL8532B Detailed description: The BL8532B is a DC/DC step-up converter with voltage type , PFM control mode , output invariablenes current. It has only three Peripheral components that is a inductor 、a output capacitor、a schottky diode and a resistor with set-up output current, that can afford to a invariant output current between 0 and 500mA . Rc set-up method： If the output current is Iout，that Rc= V IFB Iout 。 For example, want to the current value of 100mA , select the chip of VIFB=200mV, that Rc=200mV/100mA=2Ω。 Selection of the external components: Thus it can be seen, the inductor and shottky diode affect the conversion efficiency greatly. The inductor and the capacitor also have great influence on the output voltage ripple of the converter. So it is necessary to choose a suitable inductor, a capacitor and a right shottky diode, to obtain high efficiency, low ripple and low noise. D≡ Before discussion，we define: Vout − Vin Vout . （1） ）Inductor Selection Make sure DC-DC can natural work firstly in the model of the minimum continuous current that D (1 − D ) 2 R L . is Lmin，Lmin≧ 2f This formula deduce that ignoring the autoecious resistor and a diode with the forward voltage drop, but the actual value is still big. If the inductance less than Lmin, inductor will reach magnetic saturation, efficiency will greatly drop, and hardly output steady voltage. Secondly , considering the current ripple of the inductor, ignoring the autoecious parameter in the mode of continuous current. ∆I= Vin D • Vin DVin + ， Imax= 2 (1 − D) R L 2 Lf Lf . When “L” is too small, will lead to high current ripple of the inductor , and the maximum current of the inductor , schottky diode , power tube of the chip are excessive . Thirdly, generally speaking, not considering efficiency , small inductor can drive load more then large inductor .But in the same load conditions , large inductor with the current ripple and the maximum current value are small. So the large inductor should be able to start up circuit in the low input voltage. Use inductor with an inductance of 10μH or more ,it’s ensure to normal work . If output port has load with output large current (for example: output current is more than 50mA), for improving to efficiency, suggest to use large inductor. At the same time, in the large load, the resistor is in series with the inductor that will affect the switching efficiency. Supposed , the resistor is rL，Rload，that the power consumption as follow： ∆η ≈ rL Rload（1 − D）2 http://www.belling.com.cn - 5Total 13 Pages 2/20/2013 BL8532B For example, input 1.5V, output 3.0V, load 20 Ω (150mA),rL=0.5Ω,efficiency loss 10% . Considering, suggest to use an inductance of 15 uH , <0.5Ω. （2） ）Capacitor Selection No considering the inductor with equivalent series resistor(ESR), output voltage ripple is： r= D ∆Vout = Vout Rload Cf considering the inductor’s ESR, the output ripple will be increase： r′ = r + Im ax • R ESR Vout Suggest to use Tantalum type with the low ESR or more parallel-resistor. （3） ）Diode Selection It is recommended that the diode have great effect to DC-DC efficiency, we suggest to use schottky diode with the lower positive turn-on voltage and the lower corresponsive time. For example, 1N5817、1N5819 . （4） ）Input Capacitor Power supply is stably, even if no input capacitor, DC-DC can output voltage with the lower ripple and the lower noise. But we suggest to connect with the capacitor of 10uF or more when the power supply was far away DC-DC, for minish the output noise. （5） ）Resistor R1、 、R2 for output voltage detect Application to invariant current , the formula of R1、R2： Vout R1 = +1 V IFB R2 http://www.belling.com.cn - 6Total 13 Pages 2/20/2013 BL8532B Test circuits: (1) Feedback voltage test circuit (2) Start-up voltage test circuit（Iload=1mA） (3) Hold-on voltage test circuit（Iload=1mA） http://www.belling.com.cn - 7Total 13 Pages 2/20/2013 BL8532B (4) Quiescent current test circuit (5) Oscillator frequency and duty cycle test circuit (6) LX switching current test circuit (7) LX leakage current test circuit http://www.belling.com.cn - 8Total 13 Pages 2/20/2013 BL8532B (8) CE “H”voltage test circuit (9) CE “L”voltage test circuit http://www.belling.com.cn - 9Total 13 Pages 2/20/2013 BL8532B Package description: Package SOT-89-5 Number of each volume 1000 Unit mm Brede size： Mode (1) is the standard package; Mode (2) is customized for client. http://www.belling.com.cn - 10Total 13 Pages 2/20/2013 BL8532B http://www.belling.com.cn - 11Total 13 Pages 2/20/2013