BL8531 High Efficiency Low Noise PFM Step-up DC/DC Converter DESCRIPTION FEATURES BL8531 series are CMOS-based PFM step-up DCDC Converter. The converter can start up by supply voltage as low as 0.8V, and capable of delivering maximum 200mA output current at 3.3V output with 1.8V input Voltage. Quiescent current drawn from power source is as low as 5.5uA. All of these features make BL8531 series be suitable for the portable devices, which are supplied by a single battery to four-cell batteries. • • • • • • To reduce the noise caused by the switch regulator, BL8531 is well considerate in circuit design and manufacture, so that the interferer to other circuits by the device is reduced greatly. • • BL8531 integrates stable reference circuits and trimming technology, so it can afford high precision and low temperature-drift coefficient of the output voltage. Deliver 200mA at 3.3V Output voltage with 1.8V input Voltage Low start-up voltage (when the output current is 1mA)-----------------------------0.8V Output voltage can be adjusted from 2.5V～ 6.0V (In 0.1V step) Output voltage accuracy ---------------±2％ Low temperature-drift coefficient of the output voltage--------------------±100ppm/℃ Only three external components are necessary: An inductor, a Schottky diode and an output filter capacitor High power conversion efficiency-----85％ Low quiescent current drawn from power source-------------------------------------<5.5uA APPLICATIONS • BL8531 is available in SOT-89-3, SOT-23-3, SOT23-5 and TO-92 packages, which is PB free. And in 5-pin packages, such as SOT-23-5, the device can be switch on or off easily by CE pin, to minimize the standby supply current. • • TYPICAL APPLICATION Power Source for PDA, DSC, MP3 Player, Electronic toy and wireless mouse Power Source for a Single or Dual-cell Battery-Powered Equipments Power Source for LED ELECTRICAL CHARACTERISTICS Output Voltage VS. Output Current (Vout=3.3V) 4.0 3.5 3.0 Vout (V) BL8531 2.5 Vin=0.9V Vin=1.0V Vin=1.2V Vin=1.5V Vin=1.8V Vin=2.0V Vin=2.5V 2.0 1.5 1.0 0.5 0.0 0 www.belling.com.cn 1 0.1 0.2 0.3 Iout (A) 0.4 0.5 BL8531 ORDERING INFORMATION BL8531 □ 1 □ 2 □ 3 □ 4 Code 1 □ □ 2 3 □ 4 □ MARKING INFORMATION Product Classification Description Temperature&Rohs: C: -40~85°C, Pb Free Rohs Std. Package type: B3: SOT-23-3 B5: SOT-23-5 C3: SOT-89-3 H: TO-92 Packing type: TR: Tape&Reel (Standard) BG: Bag (TO-92) Output voltage: e.g. 25=2.5V 33=3.3V 60=6.0V Marking 30:Product Code 30XX XX: Output Voltage Product Classification 30:Product Code 30XX XX: Output Voltage Product Classification LA: Product Code Value XX: Output Voltage LAXX YYBZZ ZZ: Date Code Product Classification Marking LA: Product Code XX: Output Voltage LAXX YYBZZ OUT Output Feedback Pin, Power supply for internal LX Switching Pin NC No Connection www.belling.com.cn YY: LOT NO. B: FAB Code ZZ: Date Code Chip Enable (Active high) Ground YY: LOT NO. B: FAB Code PIN CONFIGURATION GND BL8531CC3TR□□ Marking output Voltage Range -0.3V-12V LX Voltage -0.3V-6.5V CE Pin Voltage -0.3V-(Vout+0.3) Lx Pin Output Current 0.7A Operating Junction 125°C Temperature (Tj) Ambient Temperature (Ta) -40°C -85°C Power SOT-23-3 250mW Dissipation SOT-23-5 250mW SOT-89-3 500mW TO-92 500mW Storage Temperature (Ts) -40°C -150°C Lead Temperature & Time 260°C, 10S Note: Exceed these limits to damage to the device. Exposure to absolute maximum rating conditions may affect device reliability. CE BL8531CB5TR□□ Marking ABSOLUTE MAXIMUM RATING Parameter BL8531CB3TR□□ 2 BL8531CHBG□□ BL8531 RECOMMENDED WORK CONDITIONS Item Min Recommended 0.8 10 0 47 -40 27 ≥10 100 Input Voltage Range Inductor Input Capacitor Output Capacitor Ambient Temperature Max. Unit Vout 100 V μH μF μF °C 220 85 ELECTRICAL CHARACTERISTICS SYMBOL ITEM Vout Output Voltage Vin Input Voltage Iin Input Current Vstart Start-up voltage Vhold Hold-on voltage IDD Rswon ILXleak VCEH VCEL Fosc Maxdty η Quiescent current drawn from power source Switch ON Resistance LX leakage current CE “H” threshold voltage CE “H” threshold voltage Oscillator frequency Oscillator duty cycle Efficiency TEST CONDITIONS 2.45 2.646 2.94 3.234 3.528 3.92 4.9 5.88 Iout=0mA， Vin=Vout*0.6 Iout=1mA， Vin：0→2V Iout=1mA， Vin：2→0V Without external components, Vout =Vout×1.05 0.6 REFERENCE DATA Typ Max 2.5 2.7 3.0 3.3 3.6 4.0 5.0 6.0 V 12 15 uA 0.8 0.9 V 0.7 0.5 VCE：0→2V 7 5 0.3 400 70 75 85 3 uA V VCE： 2→0V On（Vlx“L”）side uA Ω 0.8 LX on “L” side Vout=Vout*0.96 V V 0.5 Vout=Vlx=6.5V UNIT 2.55 2.754 3.06 3.366 3.672 4.08 5.1 6.12 Vout 4 Note： 1. Diode: Schottky type, such as: 1N5817, 1N5819, 1N5822 2. Inductor: 27uH(R<0.5Ω) 3. Capacitor: 100uF(Tantalum type) www.belling.com.cn Min V Khz 80 ％ ％ BL8531 BLOCK DIAGRAM Note: CE pin is only available on 5 pins packages. DETAILED DESCRIPTION The BL8531 series are boost structure, voltagetype Pulse-Frequency Modulation (PFM) step-up DC-DC converter. Only three external components are necessary: an inductor, an output filter capacitor and a schottky diode. And the converter’s low noise and low ripple output voltage can be adjusted from 2.5V to 5.0V, 0.1V step. By using the depletion technics, the quiescent current drawn from power source is lower than 7uA. The high efficiency device consists of resistors for output voltage detection and trimming, a start-up voltage circuit, an oscillator, a reference circuit, a PFM control circuit, a switch protection circuit and a driver transistor. inside BL8531 provides fixed frequency and pulse width wave. The reference circuit provides stable reference voltage to output stable output voltage. Because internal trimming technology is used, The chip output change less than ±2%. At the same time， the problem of temperature-drift coefficient of output voltage is considered in design, so temperature-drift coefficient of output voltage is less than 100ppm/℃。 The PFM control circuit is the core of the BL8531 IC. This block controls power switch on duty cycle to stabilize output voltage by calculating results of other blocks which sense input voltage, output voltage, output current and load conditions. In PFM modulation system, the frequency and pulse width is fixed. The duty cycle is adjusted by skipping pulses, so that switch on-time is changed based on the conditions such as input voltage, output current and load. The oscillate block Though at very low load condition, the quiescent current of chip do effect efficiency certainly. The four main energy loss of Boost structure DC-DC converter in full load are the ESR of inductor, the voltage of Schottky diode, on resistor of internal N-channel MOSFET and its driver. In order to improve the efficiency, BL8531 integrates low onresistor N-channel MOSFET and well design driver circuits. The switch energy loss is limited at very low level. www.belling.com.cn High-gain differential error amplifier guarantees stable output voltage at difference input voltage and load. In order to reduce ripple and noise, the error amplifier is designed with high band-with. 4 BL8531 SELECTION THE EXTERNAL COMPONENTS An inductor value of 3uH to 1mH works well in most applications. If DC-DC converter delivers large output current (for example: output current is great than 50mA), large inductor value is recommended in order to improve efficiency. If DC-DC must output very large current at low input supply voltage, small inductor value is recommended. Thus it can be seen, the inductor and schottky 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 schottky diode, to obtain high efficiency, low ripple and low noise. Before discussion，we define D≡ Vout − Vin . Vout The ESR of inductor will affect efficiency greatly. Suppose ESR value of inductor is rL，Rload is load resistor，then the energy can be calculated by following expression: INDUCTOR SELECTION Above all, we should define the minimum value of the inductor that can ensure the boost DC-DC to operate in the continuous current-mode condition. ∆η ≈ For example: input 1.5V, output is 3.0V, Rload=20Ω, rL=0.5Ω, The energy loss is 10%. Consider all above，inductor value of 47uH、 ESR<0.5Ω is recommended in most applications. Large value is recommended in high efficiency applications and smaller value is recommended. D(1 − D) 2 RL L min ≥ 2f The above expression is got under conditions of continuous current mode, neglect Schottky diode’s voltage, ESR of both inductor and capacitor. The actual value is greater that it. If inductor’s value is less than Lmin，the efficiency of DC-DC converter will drop greatly, and the DCDC circuit will not be stable. CAPACITOR SELECTION Ignore ESR of capacitor，the ripple of output voltage is: r= Secondly, consider the ripple of the output voltage, ∆Vout D = Vout Rload Cf So large value capacitor is needed to reduce ripple. But too large capacitor value will slow down system reaction and cost will improve. So 100uF capacitor is recommended. Larger capacitor value will be used in large output current system. If output current is small (<10mA), small value is needed. D • Vin ∆I = Lf Vin DVin + Im ax = 2 2 Lf (1 − D) R L If inductor value is too small, the current ripple through it will be great. Then the current through diode and power switch will be great. Because the power switch on chip is not ideal switch, the energy of switch will improve. The efficiency will fall. Consider ESR of capacitor，ripple will increase： r' = r + Im ax • R ESR Vout When current is large, ripple caused by ESR will be main factor. It may be greater than 100mV。 The ESR will affects efficiency and increase energy loss. So low-ESR capacitor (for example: tantalum capacitor) is recommend or connect two or more filter capacitors in parallel. Thirdly ， in general, smaller inductor values supply more output current while larger values start up with lower input voltage and acquire high efficiency. www.belling.com.cn rL Rload (1 − D) 2 5 BL8531 DIODE SELECTION INPUT CAPACTITOR Rectifier diode will affects efficiency greatly， Though a common diode (such as 1N4148) will work well for light load，it will reduce about 5%~10% efficiency for heavy load，For optimum performance, a Schottky diode (such as 1N5817、 1N5819、1N5822) is recommended. If supply voltage is stable, the DC-DC circuit can output low ripple, low noise and stable voltage without input capacitor. If voltage source is far away from DC-DC circuit, input capacitor value greater than 10uF is recommended. TEST CIRCUITS Output voltage test circuit (Iload=1mA) Quiescent current test circuit (Vout=Vout_nom*1.05, R=1KΩ, C=0.1uF) BL8531 BL8531 Start-up voltage test circuit (Iload=1mA) Oscillator frequency and duty cycle test circuit (Vin=Vout*0.95，R=1KΩ) BL8531 BL8531 Hold-on voltage test circuit (Iload=1mA) BL8531 www.belling.com.cn 6 BL8531 TYPICAL PERFORMANCE CHARACTERISTICS Recommended operating conditions: Cin=47uF, Cout=47uF, Topt=25°C. unless otherwise noted) Efficiency VS. Output Current Output Voltage VS. Output Current (Vout=2.7V) (Vout=2.7V) 100.00% 3.0 90.00% 2.5 70.00% Vout (V) Efficiency 80.00% 60.00% 50.00% Vin=0.9V Vin=1.0V Vin=1.2V Vin=1.5V Vin=1.8V Vin=2.0V 40.00% 30.00% 20.00% 10.00% 0.00% 0.001 2.0 1.5 Vin=0.9V Vin=1.0V Vin=1.2V Vin=1.5V Vin=1.8V Vin=2.0V 1.0 0.5 0.0 0.01 0.1 1 0 0.1 0.2 Iout (A) Iout (A) 0.3 0.4 Output Voltage VS. Output Current Efficiency VS. Output Current (Vout=3.3V) (Vout=3.3V) 100.00% 4.0 90.00% 3.5 80.00% 3.0 Vout (V) Efficiency 70.00% 60.00% 50.00% Vin=0.9V Vin=1.0V Vin=1.2V Vin=1.5V Vin=1.8V Vin=2.0V Vin=2.5V 40.00% 30.00% 20.00% 10.00% 0.00% 0.001 2.5 Vin=0.9V Vin=1.0V Vin=1.2V Vin=1.5V Vin=1.8V Vin=2.0V Vin=2.5V 2.0 1.5 1.0 0.5 0.0 0 0.01 0.1 0.1 0.2 1 Iout (A) Efficiency VS. Output Current 0.3 Iout (A) 0.4 0.5 Output Voltage VS. Output Current (Vout=5.0V) (Vout=5.0V) 100.00% 6.0 90.00% 5.0 70.00% 4.0 60.00% 50.00% Vin=1.5V 40.00% Vin=1.6V 30.00% Vin=1.8V Vin=1.5V Vin=1.6V Vin=1.8V Vin=2.0V Vin=2.5V Vin=3.0V 2.0 1.0 Vin=2.5V 10.00% Vin=3.0V 0.0 0.01 0.1 1 Iout (A) www.belling.com.cn 3.0 Vin=2.0V 20.00% 0.00% 0.001 Vout (V) Efficiency 80.00% 0 0.1 0.2 Iout (A) 7 0.3 BL8531 Ripple Voltage VS. Output Current Ripple Voltage VS. Output Current (Vout=2.7V) (Vout=3.3V) 180 250 Ripple Voltage(mV) 160 Output Ripple (mV) 140 120 100 Vin=0.9 Vin=1.0 Vin=1.2 Vin=1.5 Vin=1.8 Vin=2.0 80 60 40 20 200 150 Vin=0.9 Vin=1.0 Vin=1.2 Vin=1.5 Vin=1.8 Vin=2.0 Vin=2.5 100 50 0 0 0 0.1 0.2 0.3 0.4 0 0.1 0.2 0.3 Output Current (mA) Output Current (A) Ripple Voltage VS. Output Current 0.4 0.5 Iin (no load) VS. Input Voltage (Vout=5.0V) 160 180 Vin=1.5 Vin=1.6 Vin=1.8 Vin=2.0 Vin=2.5 Vin=3.0 Output Ripple (mV) 140 120 100 120 80 100 80 60 60 40 40 20 20 0 0.00 0 0.05 0.10 0.15 Output Current (A) 0.20 0.25 Output Voltage VS Temperature 5.0 4.0 3.0 2.0 Vout=2.7V Vout=3.3V Vout=5.0V 1.0 0.0 -40 10 60 110 160 Temp (℃ ℃) www.belling.com.cn 0 1 2 Input Voltage （V） ） 6.0 Output Voltage (V) Vout=2.7V Vout=3.3V Vout=5.0V 140 Iin (uA） ） 160 8 3 4 BL8531 PACKAGE OUTLINE Package SOT-23-3 Devices per reel 3000Pcs Unit mm 3000Pcs Unit mm Package dimension： Package SOT-23-5 Devices per reel Package specification： www.belling.com.cn 9 BL8531 Package SOT-89-3 Devices per reel 1000Pcs Unit mm TO-92 Devices per Bag 1000Pcs Unit mm Package Dimension: Package Package Dimension: www.belling.com.cn 10