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Document overview
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Technical content
Features
Wide Input Range: 2.5-6V Input Up to 1.5A Output Current Maximum 8V Output Voltage 1.2MHz Switching Frequency Low RDS(ON): 70mΩ Up to 90% Efficiency Under-Voltage Lockout Protection Over-Temperature Protection Internal Soft Start 1uA Shutdown Current Accurate Reference: 0.6V VREF Compact package: SOT23-6
Applications
Chargers LCD Displays Digital Cameras Handheld Devices Portable Products
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com.cn • Page 2 9/4/2012 SE3608 2A/1.2Mhz Output Current, Boost C onverter Pin Configuration Pin Description NO. Pin Name Pin Function Description 1 SW Power Switch Output. Connect the inductor and the blocking Schottky diode to SW.
2 GND GND
3 FB Feedback
Enable pin. A high input at EN enables the device and a low input disables the devices. When not used, connect EN to the input source for automatic startup. 5 IN Input Supply Pin. Must be locally bypassed.
6 NC No Internal Connection
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com.cn • Page 3 9/4/2012 SE3608 2A/1.2Mhz Output Current, Boost C onverter Absolute Maximum Ratings Symbol Parameter Maximum Units VIN VIN Supply Voltage -0.3～6.5 V VSW Voltage at SW Pin -0.5～12 V VIO All Other I/O Pins GND-0.3 to VDD+0.3 V PTR1 Thermal Resistance(SOT23-6) ΘJA 220 ℃/W Tstg Storage Temperature -55 to 150 ℃ Tsolder Package Lead Soldering Temperature（10s） 260 ℃ ESD Susceptibility HBM(Human Body Mode) 2 kV Note: Exceeding these ratings may damage the device. Recommended Operating Conditions Symbol Parameter Maximum Units VIN Input Voltage 2.5 to 6 V VSW Output Voltage VIN to 10 V TA Ambient Temperature -40 to +85 ℃ TJ Junction Temperature -40 to +125 ℃ Note: The device is not guaranteed to function outside of its operating rating.
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com.cn • Page 4 9/4/2012 SE3608 2A/1.2Mhz Output Current, Boost C onverter
Electrical Characteristics
（VIN = 3.3V, VOUT=5V, IOUT=100mA, TA = 25°C unless otherwise specified） Symbol Parameter Conditions Min. Typ. Max. Unit VIN Input Voltage 2.5 6 V Feedback VFB Feedback Voltage 588 600 612 mV Ibias FB Pin Input Bias Current 0.05 1 µA UVLO UVLO Under Voltage Lock Out 2.1 V Operating Current Ioff Operating Current（Shutdown） 0.1 1 µA Isby No Switching Vin=3V VFB=0.7V 100 µA Fsw Switching Frequency 1.2 MHz Dmax Maximum Duty Cycle VFB=0V 90 % Chip Enable VEN_H EN Minimum High Level 1.5 V VEN_L EN Maximum Low Level 0.4 V VHYS EN Hysteresis 90 mV IEN EN Input Bias Current 1 µA OTP OTP 120 ℃ OTP Hysteresis 20 ℃ Output Switch RON SW On Resistance (Note 3) 70 mΩ ILIMIT SW Current Limit 5 A ILEAK SW Leakage Current Vsw＝5V 0.01 1 µA Open Circuit Protection VOV SE3608 VOUT×112% V Soft Start tss Soft Start Time (Note 3) VIN Power On 400 µS Note3: Guaranteed by design.
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com.cn • Page 5 9/4/2012 SE3608 2A/1.2Mhz Output Current, Boost C onverter Typical Performance Characteristics I Load / A Efficiency / % Current Load Vs Efficiency Vin=3.6V,Vout=5V Fig 1 Efficiency Vs Light Load 0 0.5 1 1.5 2 2.5 I Load / A Efficiency / % Current Load Vs Efficiency Vin=3.6V,Vout=5V Fig 2 Efficiency Vs Heavy Load Fig 3 Startup with Vin Fig 4 SW Waveform Fig 5 Transient Response (VIN=3.6V, Vout=5V, Iload=0.9A to 0.15A) Fig 6 Transient Response (VIN=3.6V, Vout=5V, Iload=0.15A to 0.9A) Fig 7 Vout Ripple Fig 8 Quiescent Current Vs Temperature
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com.cn • Page 6 9/4/2012 SE3608 2A/1.2Mhz Output Current, Boost C onverter Operation Description The SE3608 adopts a fixed frequency, peak current mode boost regulator architecture to regulate output voltage. The operating principle of the SE3608 can be easily understood by referring to the functional block diagram. At the beginning of each oscillator cycle the MOSFET is turned on by the control circuit. To prevent sub-harmonic oscillations at duty cycle larger than 50 percent, a stabilizing ramp is added to the output of the current sense amplifier and the result is fed into the negative input of t he PWM comparator. When this voltage equals the output voltage of the error amplifier, the power MOSFET is turned off. The voltage at the output of the error amplifier is an amplified result of the difference between the 0.6V reference voltage and the feedback voltage. In this way the peak current level keeps the output voltage in regulation. If the feedback voltage starts to drop, the output of the error amplifier increases, resulting in more current to flow through the power MOSFET, thus increasing the power delivered to the output. The SE3608 has internal soft start to avoid rush input current during the startup and also to avoid overshoot on the output. Applications Information Because of the high integration in the SE3608, the application circuit based on this regulator IC is rather simple. Only input capacitor C IN, output capacitor C OUT1 and COUT2, inductor L, S chottky diode and feedback resistors (R1 and R2) need to be selected for the targeted applications. Feedback Resistor Divider R1 and R2: R1 and R2 should be chosen to program the proper output voltage. To minimize the power consumption under light loads, it is desirable to choose large resistance values for both R1 and R2. A value of between 330KΩ and 5MΩ is recommended for both resistors. If R1=440KΩ is chosen, then R2 can be calculated to be 60 KΩ based on the following equation: R2 = (R1×0.6V)/(VOUT - 0.6V) Feedback Capacitor CFB: In order to enhance response speed of the convertor, feedback capacitor C FB should be added to the loop. Its value should not be less than 22pF. Input Capacitor CIN: To minimize the potential noise problem, place a typical X5R or better grade ceramic capacitor really close to the IN and GND pins. Care should be taken to minimize the loop area formed by CIN, and IN/GND pins. In this case a 10uF low ESR ceramic is recommended.
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com.cn • Page 7 9/4/2012 SE3608 2A/1.2Mhz Output Current, Boost C onverter Output Capacitor COUT1 and COUT2: The output capacitor is selected to meet the output ripple noise requirements. Both steady state ripple and transient requirements must be taken into c onsideration when selecting these capacitors. For the best performance, it is recommended C OUT1 should be X5R or better grade ceramic capacitor with 10V rating and more than two pieces of 22uF Capacitors. Only when COUT1 is big enough, it can absorb the energy of inductor and prevent the Vout to shoot up too high when there is a sudden reduction in the current load. It is recommended COUT2 is 100nF. It can also reduce the ripple of output voltage. Boost Inductor L: The recommended value of inductor is 1u H. Small size and better efficiency are the major concerns for portable devices. The inductor should have low core loss at 1.2MHz and low DCR for better efficiency. To avoid inductor saturation the current rating should be considered. Diode Selection: Schottky diode is a good choice for SE3608 because of its low forward voltage drop and fast reverses recovery in order to get better efficiency. The high speed rectification is also a good characteristic of Schottky diode for high switching frequency. The diode reverse breakdown voltage should be larger than the output voltage, and its forward voltage should be less than 0.6V. Start-up and Inrush Current: The SE3608 has internal soft start to limit the value of current through V IN during the startup and also to avoid overshoot on the output. The soft start is realized by gradually increasing the output of error amplify during start-up. Over Voltage Protection: The SE3608 has integrated over voltage protection function. If the output voltage exceeds the predetermined value of 12%, the internal circuit will shut power MOS, until V OUT voltage falls down.
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com.cn • Page 8 9/4/2012 SE3608 2A/1.2Mhz Output Current, Boost C onverter Outline Drawing For SOT23-6 联系方式： 北京思旺电子技术有限公司–中国总部 地址：中国北京市海淀区信息路 22 号上地科技综合楼 B 座二层 邮编：100085 电话:010-82895700/1/5 传真:010-82895706 Seaward Electronics Corporation – 台湾办事处 2F, #181, Sec. 3, Minquan East Rd, Taipei, Taiwan R.O.C 电话: 886-2-2712-0307 传真: 886-2-2712-0191 Seaward Electronics Incorporated – 北美办事处 1512 Centre Pointe Dr. Milpitas, CA95035, USA 电话: 1-408-821-6600