BL3406B 1.5 MHz, 800mA Synchronous Buck Converter • FEATURES • • • • • • • • • • • • DESCRIPTION High Efficiency: Up to 96% 1.5MHz Constant Switching Frequency Current Mode Operation for Excellent Line and Load Transient Response No Schottky Diode Required 2.5V to 5.5V Input Voltage Range 1.0V,1.2V,1.5V,1.8V,2.5V and 3.3V Fixed/Adjustable Output Voltage 100% Duty Cycle in Dropout Mode Low Quiescent Current: 180µA Over temperature Protection Short Circuit Protection Shutdown Quiescent Current < 1µA Space Saving 5-Pin Thin SOT23 Package The BL3406B is a constant frequency, 1.5MHz, slope compensated current mode PWM step-down converter working under an input voltage range of 2.5V to 5.5V. This feature makes the BL3406B suitable for single cell Li-ion battery-powered applications. The internal synchronous rectifier is desired to increase efficiency without an external Schottky diode. 100% duty cycle capability extends battery life in portable devices, while the quiescent current is 180µA at no load, and drops to < 1µA in shutdown. Pulse Skipping Mode operation increases efficiency at light loads, further extending battery life. The BL3406B is offered in a low profile (1mm) 5-pin, thin SOT23 package, and is available in an adjustable version and fixed output versions of 1.0V, 1.2V, 1.5V , 1.8V, 2.5V and 3.3V. APPLICATIONS • • • • • • • GPS Receivers Cellular and Smart Phones Wireless Handsets and DSL Modems Microprocessors and DSP Core Supplies PDAs Digital Still and Video Cameras MP3/MP4/MP5 Players Portable Instruments ORDERING INFORMATION TYPICAL APPLICATION BL3406B –XX X XXX Package： TRN: TSOT23-5 RN: SOT23-5 Features: P: Standard (default, lead free) C: Customized Output Voltage： 10: 1.0V 12: 1.2V 15: 1.5V 18: 1.8V 25: 2.5V 33: 3.3V AD: Adjustable PPMIC BU BL3406B Rev 1.5 10/2009 2.7V - 4.2V VIN 4 C1 4.7uF SW VIN 3 BL3406B-ADJ 1 VFB 5 Run GND 2 L1 2.2 µH C3 22pF VOUT 1.8V C2 10uF R2 200k R1 100k Figure 1. BL3406B-ADJ Typical Application Circuit www.belling.com.cn Belling Proprietary Information. Unauthorized Photocopy and Duplication Prohibited ©2009 Belling All Rights Reserved 1 BL3406B 1.5 MHz, 800mA Synchronous Buck Converter Absolute Maximum Rating (Note 1) Input Supply Voltage…………………-0.3V to +6V RUN, VFB Voltages……………………-0.3V to +VIN SW Voltages……………………-0.3V to (VIN+0.3V) P-Channel Switch Source Current (DC) ………1A N-Channel Switch Sink Current (DC) …………1A Peak SW Sink and Source Current……………1.4A Operating Temperature Range……-40°C to +85°C (Note2) Junction Temperature ………………+125°C Storage Temperature Range………-65°C to +150°C Lead Temperature (Soldering, 10s) ………+300°C Package Information Adjustable Output Version RUN SOT23-5 SOT23-5 TOP VIEW TOP VIEW 1 5 Y Year RUN GND 2 3 4 Top Mark (Note3) AJYW SW VIN 3 Part Number BL3406B-1.0V BL3406B-1.2V BL3406B-1.5V BL3406B-1.8V BL3406B-2.5V BL3406B-3.3V Temp Range -40°C to +85°C 9 2009 A 2010 B 2011 C 2012 D 2013 1 A … … 26 Y 27 Z 28 a W Week 1 … … 53 y 5 VOUT 4 VIN MARKING Part Number BL3406B-Adj VFB MARKING GND 2 SW Fixed Output Versions Top Mark AAYW ABYW ACYW ADYW AEYW AFYW Temp Range -40°C to +85°C 54 z Thermal Resistance (Note 4) Package TSOT23-5 SOT23-5 ӨJA 220°C/W 250°C/W ӨJC 110°C/W 130°C/W Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula: TJ = TA + (PD) x (220°C/W). Note 3: Y: Year of wafer manufacturing W: Week of wafer manufacturing Note 4: Thermal Resistance is specified with approximately 1 square of 1 oz copper. PPMIC BU BL3406B Rev 1.5 10/2009 www.belling.com.cn Belling Proprietary Information. Unauthorized Photocopy and Duplication Prohibited ©2009 Belling All Rights Reserved 2 BL3406B 1.5 MHz, 800mA Synchronous Buck Converter Pin Description PIN NAME 1 RUN 2 GND 3 SW 4 VIN 5 VFB/VOUT FUNCTION Regulator Enable Control Input. Drive RUN above 1.5V to turn on the part. Drive RUN below 0.3V to turn it off. In shutdown, all functions are disabled drawing <1µA supply current. Do not leave RUN floating. Ground Power Switch Output. It is the switch node connection to external inductor. This pin connects to the drains of the internal P-Channel and N-Channel MOSFET switches. Supply Input Pin. Must be closely decoupled to GND, Pin 2, with a 2.2µF or greater ceramic capacitor. VFB (BL3406B-Adj): Feedback Input Pin. Connect FB to the center point of the external resistor divider. The regulated voltage on this pin is 0.6V. VOUT (BL3406B-1.2/BL3406B-1.5/BL3406B-1.8): Output Voltage Feedback Pin. An internal resistive divider divides the output voltage down for comparison to the internal reference voltage. Block Diagram PPMIC BU BL3406B Rev 1.5 10/2009 www.belling.com.cn Belling Proprietary Information. Unauthorized Photocopy and Duplication Prohibited ©2009 Belling All Rights Reserved 3 BL3406B 1.5 MHz, 800mA Synchronous Buck Converter Electrical Characteristics (Note 5) (VIN =VRUN= 3.6V, TA = 25°C, unless otherwise noted.) Parameter Conditions Input Voltage Range Input DC Supply Current Active Mode VFB=0.5V or VOUT=90% Shutdown Mode VFB=0V, VIN=4.2V TA = +25°C Regulated Feedback TA= 0°C ≤ TA ≤ 85°C Voltage TA= -40°C ≤ TA ≤ 85°C VFB Input Bias Current VFB = 0.65V Reference Voltage Line Regulation VIN = 2.5V to 5.5V Regulated Output Voltage Output Overvoltage Lockout Output Voltage Line Regulation Output Voltage Load Regulation TYP MAX Unit 5.5 V 300 1.0 0.6120 0.6135 0.6150 µA µA V V V ±30 nA 0.04 0.4 %/V 2.5 0.5880 0.5865 0.5850 180 0.1 0.6000 0.6000 0.6000 BL3406B-1.2, -40°C ≤ TA ≤ 85°C BL3406B-1.8, -40°C ≤ TA ≤ 85°C ∆VOVL = VOVL – VFB, Adjustable Version 1.164 1.746 20 1.200 1.800 50 1.236 1.854 80 V V mV ∆VOVL = VOVL – VOUT, Fixed Version 2.5 7.8 13 % 0.04 0.40 % VIN = 2.5V to 5.5V Oscillator Frequency RDS(ON) of P-CH MOSFET VIN=3V, VFB=0.5V or VOUT=90% Duty Cycle <35% VFB=0.6V or VOUT=100% ISW = 300mA RDS(ON) of N-CH MOSFET Peak Inductor Current MIN 1.2 0.5 % 1.2 A 1.5 0.40 1.8 0.50 MHz Ω ISW = -300mA 0.35 0.45 Ω SW Leakage Current VRUN = 0V, VSW = 0V or 5V, VIN = 5V ±0.01 ±1 µA RUN Threshold RUN Leakage Current -40°C ≤ TA ≤ 85°C 1.1 ±0.01 1.30 ±1 V µA 0.3 Note 5: 100% production test at +25°C. Specifications over the temperature range are guaranteed by design and characterization. PPMIC BU BL3406B Rev 1.5 10/2009 www.belling.com.cn Belling Proprietary Information. Unauthorized Photocopy and Duplication Prohibited ©2009 Belling All Rights Reserved 4 BL3406B 1.5 MHz, 800mA Synchronous Buck Converter Typical Performance Characteristics (Test Figure 1 above unless otherwise specified) Efficiency vs. Output Current Output Voltage vs. Load Current 2.2 90 VOUT=1.8V L=2.2uH 80 2.0 Output Voltage(V) Efficiency(%) VIN=3.6V TA=25°C 2.1 70 60 50 40 20 0.1 1.8 1.7 1.6 1.5 Vin=2.7V Vin=3.6V Vin=4.2V 30 1.9 1.4 1.3 1 10 100 1000 0 200 400 Output Current(mA) 800 1000 1200 Output Voltage vs. Input Voltage Reference Voltage vs. Temperature 0.606 1.820 VIN=3.6V ILOAD=10mA ILOAD=100mA ILOAD=600mA 1.815 0.605 1.810 VOUT(V) Reference Voltage(V) 600 Load Current(mA) 0.604 1.805 1.800 1.795 0.603 1.790 1.785 0.602 -50 -25 0 25 50 75 100 125 1.780 2.7 3.0 3.3 3.6 3.9 4.2 4.5 4.8 5.1 Temperature(°C) VIN(V) Supply Current vs. Supply Voltage Start_up from Shutdown 5.4 5.7 245 VOUT=1.8V ILOAD=0A TA=25°C Dynamic Supply Current(uA) 240 235 230 225 220 215 210 205 200 195 2 3 4 5 6 Supply Voltage(V) PPMIC BU BL3406B Rev 1.5 10/2009 www.belling.com.cn Belling Proprietary Information. Unauthorized Photocopy and Duplication Prohibited ©2009 Belling All Rights Reserved 5 BL3406B 1.5 MHz, 800mA Synchronous Buck Converter Load Step Load Step Load Step Load Step Pulse Skipping Mode PPMIC BU BL3406B Rev 1.5 10/2009 Output Short www.belling.com.cn Belling Proprietary Information. Unauthorized Photocopy and Duplication Prohibited ©2009 Belling All Rights Reserved 6 BL3406B 1.5 MHz, 800mA Synchronous Buck Converter Operation The BL3406B uses a constant frequency, current mode step-down architecture. Both the main switch (P-channel MOSFET) and the synchronous rectifier (N-channel MOSFET) are integrated internally. This Step-Down DC-DC Converter can supply 800mA output current over a wide input voltage range from 2.5V to 5.5V. The over voltage comparator OVDET guards against transient overshoots >7.8% by turning the main switch off and keeping it off until the fault is removed. value of the output voltage, the BL3406B will keep the main switch on for more than one switching cycle and increases the duty cycle (Note 6) until it reaches 100%. The output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. At low input supply voltage, the RDS(ON) of the P-Channel MOSFET increases, and the efficiency of the converter decreases. Caution must be exercised to ensure the heat dissipated not to exceed the maximum junction temperature of the IC. Note 6: The duty cycle D of a step-down converter is defined as: D = TON × f OSC × 100% ≈ Current Mode PWM Control Slope compensated current mode PWM control provides stable switching and cycleby-cycle current limit for excellent load and line responses. During normal operation, the internal main switch is turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and turned off when the peak inductor current reaches the controlled value. When the main switch is off, the synchronous rectifier will be turned on immediately and stay on until either the inductor current starts to reverse, as indicated by the current reversal comparator, IRCMP, or the beginning of the next clock cycle. VOUT × 100% VIN where TON is the main switch on time, and fOSC is the oscillator frequency (1.5MHz). Short Circuit Protection The BL3406B has short circuit protection. When output is shorted to ground, the oscillator frequency is reduced to prevent the inductor current from increasing beyond the PFET current limit. The PFET current limit is also reduced to lower the short circuit current. The frequency and current limit will return to the normal values once the short circuit condition is removed and the feedback voltage reaches 0.6V. Pulse Skipping Mode Operation Maximum Load Current At very light loads, the BL3406B will automatically enter Pulse Skipping Mode to increase efficiency, further extending battery life. In this mode, the control loop skips PWM pulses while maintaining output in regulation, and the switching frequency depends on the load condition. This is a kind of PFM mode operation. The BL3406B will operate with input supply voltage as low as 2.5V, however the maximum load current decreases at lower input voltage due to large IR drop on the main switch and synchronous rectifier. Dropout Operation When the input voltage decreases toward the PPMIC BU BL3406B Rev 1.5 10/2009 www.belling.com.cn Belling Proprietary Information. Unauthorized Photocopy and Duplication Prohibited ©2009 Belling All Rights Reserved 7 BL3406B 1.5 MHz, 800mA Synchronous Buck Converter Application Information Figure 2 below shows the basic application circuit with BL3406B fixed output versions. 2.7V - 4.2V VIN 4 C1 4.7uF SW VIN 3 L1 2.2 µH VOUT 1.8V C2 10uF BL3406B-18 1 VOUT 5 Run GND 2 Figure 2. Basic Application Circuit with fixed output versions Input Capacitor Selection Setting the Output Voltage Figure 1 above shows the basic application circuit with BL3406B adjustable output version. The external resistor sets the output voltage according to the following equation: R2 ) R1 Table 1—Resistor Selection vs. Output Voltage Setting VOUT R1 R2 1.0V 180 kΩ(1%) 120 kΩ(1%) 1.2V 180 kΩ(1%) 180 kΩ(1%) 1.5V 180 kΩ(1%) 270 kΩ(1%) 1.8V 180 kΩ(1%) 360 kΩ(1%) 2.5V 158 kΩ(1%) 499 kΩ(1%) 3.3V 180 kΩ(1%) 810 kΩ(1%) VOUT = 0.6V × (1 + Inductor Selection The output inductor is selected to limit the ripple current to some predetermined value, typically 20%~40% of the full load current at the maximum input voltage. In continuous mode, the ripple current is determined by: ∆I L = V 1 VOUT (1 − OUT ) f ×L VIN A reasonable starting point for setting ripple current is ∆IL=320mA (40% of 800mA). For PPMIC BU BL3406B Rev 1.5 10/2009 output voltages above 2.0V, when efficiency at light load condition is important, the minimum recommended inductor is 2.2µH. For optimum voltage-positioning load transients, choose an inductor with DC series resistance below 150mΩ. For higher efficiency at heavy loads (above 200mA), or minimal load regulation (but some transient overshoot), the resistance should be kept below 100mΩ. The DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation. Thus, a 1120mA rated inductor should be enough for most applications (800mA+320mA). The input capacitor reduces the surge current drawn from the input and switching noise from the device. The input capacitor impedance at the switching frequency shall be less than input source impedance to prevent high frequency switching current passing to the input. In continuous mode, the source current of the main switch is a square wave of duty cycle VOUT/VIN. To prevent large voltage transients, a low ESR input capacitor sized for the maximum RMS current must be used. The maximum RMS capacitor current is given by: I RMS ≈ I OMAX [VOUT (VIN − VOUT )]0.5 VIN This formula has a maximum at VIN =2VOUT, where IRMS = IOUT/2. This simple worst-case condition is commonly used for design because even significant deviations do not offer much relief. Ceramic capacitors with X5R or X7R dielectrics are recommended due to their low ESR and high ripple current. Output Capacitor Selection The output capacitor is required to keep the output voltage ripple small and to ensure regulation loop stability. The output capacitor must have low impedance at the switching www.belling.com.cn Belling Proprietary Information. Unauthorized Photocopy and Duplication Prohibited ©2009 Belling All Rights Reserved 8 BL3406B 1.5 MHz, 800mA Synchronous Buck Converter frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended due to their low ESR and high ripple current. The output ripple ∆VOUT is determined by: ∆VOUT ≤ VOUT×(VIN −VOUT) 1 × ESR+ VIN × fOSC× L 8× fOSC×C2 Layout Considerations When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the BL3406B. These items are also illustrated graphically in Figures 5 and 6. Check the following in your layout: 2.7V - 4.2V VIN 4 C1 4.7uF SW VIN 3 BL3406B-ADJ 1 VFB 5 Run GND 2 L1 2.2 µH VOUT 1.8V C3 22pF 10/2009 VIN 4 C1 4.7uF SW VIN 3 L1 2.2 µH BL3406B-18 1 R2 200k R1 100k VOUT 1.8V C2 10uF VOUT 5 Run GND 2 Figure 4. BL3406B-1.8 Layout Circuit Figure 5. BL3406B-ADJ Suggested Layout BL3406B Rev 1.5 2.7V - 4.2V C2 10uF Figure 3. BL3406B-ADJ Layout Circuit PPMIC BU 1. The power traces, consisting of the GND trace, the SW trace and the VIN trace should be kept short, direct and wide. 2. Does the VFB pin connect directly to the feedback resistors? The resistive divider R1/R2 must be connected between the (+) plate of Cout and ground. 3. Does the (+) plate of CIN connect to VIN as closely as possible? This capacitor provides the AC current to the internal power MOSFETS. 4. Keep the switching node, SW, away from the sensitive VFB node. 5. Keep the (-) plates of CIN and COUT as close as possible. Figure 6. BL3406B-1.8 Suggested Layout www.belling.com.cn Belling Proprietary Information. Unauthorized Photocopy and Duplication Prohibited ©2009 Belling All Rights Reserved 9 BL3406B 1.5 MHz, 800mA Synchronous Buck Converter Package Description Symbol A A1 B b C D e H L Dimensions In Millimeters Min 0.889 0.000 1.397 0.356 2.591 2.692 0.838 0.080 0.300 Max 1.295 0.152 1.803 0.559 2.997 3.099 1.041 0.254 0.610 Dimensions In Inches Min 0.035 0.000 0.055 0.014 0.102 0.106 0.033 0.003 0.012 Max 0.051 0.006 0.071 0.022 0.118 0.122 0.041 0.010 0.024 SOT-23-5 Surface Mount Package PPMIC BU BL3406B Rev 1.5 10/2009 www.belling.com.cn Belling Proprietary Information. Unauthorized Photocopy and Duplication Prohibited ©2009 Belling All Rights Reserved 10 BL3406B 1.5 MHz, 800mA Synchronous Buck Converter TSOT-23-5 Surface Mount Package PPMIC BU BL3406B Rev 1.5 10/2009 www.belling.com.cn Belling Proprietary Information. Unauthorized Photocopy and Duplication Prohibited ©2009 Belling All Rights Reserved 11