MT3608

MT3608 High Efficiency 1.2MHz Current Mode Step-Up Converter FEATURES GENERAL DESCRIPTION Integrated 80mΩ Power MOSFET 2.5V to 24V Input Voltage 1.2MHz Fixed Switching Frequency Internal 4A Switch Current Limit Adjustable Output Voltage Internal Compensation Up to 28V Output Voltage Automatic Pulse Frequency Modulation Mode at Light Loads up to 93% Efficiency Available in a 6-Pin SOT23-6 Package ⚫ ⚫ ⚫ ⚫ ⚫ ⚫ ⚫ ⚫ ⚫ ⚫ APPLICATIONS ⚫ ⚫ ⚫ ⚫ ⚫ Battery-Powered Equipment Set-Top Boxed LCD Bais Supply DSL and Cable Modems and Routers Networking cards powered from PCI or PCI express slots The MT3608 is a constant frequency, 6-pin SOT23 current mode step-up converter intended for small, low power applications. The MT3608 switches at 1.2MHz and allows the use of tiny, low cost capacitors and inductors 2mm or less in height. Internal soft-start results in small inrush current and extends battery life. The MT3608 features automatic shifting to pulse frequency modulation mode at light loads. The MT3608 includes under-voltage lockout, current limiting, and thermal overload protection to prevent damage in the event of an output overload. The MT3608 is available in a small 6pin SOT-23 package. TYPICAL APPLICATION VIN CIN 22μF SW MT3608 EN GND FB D 100 VOUT=5V VOUT=5V 95 R1 110k 1% R2 15k 1% COUT 22μF 90 Efficiency(%) L 4.7μH VIN 85 80 VIN=3V VIN=3.7V 75 VIN=4.2V 70 Figure 1. Basic Application Circuit MT3608 Rev 3.1 0 200 400 600 800 1000 Load Current(mA) www.aerosemi.com Aerosemi Proprietary Information.Unauthorized Photocopy and Duplication Prohibited. All Rights Reserved. 1 MT3608 ABSOLUTE MAXIMUM RATINGS (Note 1) VIN,EN voltages……………………-0.3V to 26V FB Voltages………………................-0.3V to 6V SW Voltage…………………….…...-0.3V to 30V Power Dissipation…………………………...0.6W Thermal Resistance θJC………………..130°C/W Thermal Resistance θJA………………..250°C/W Junction Temperature(Note2)…….............160°C Operating Temperature Range…..-40°C to 85°C Lead Temperature(Soldering,10s)……......260°C Storage Temperature Range…...-65°C to 150°C ESD HBM(Human Body Mode)……………...2kV ESD MM(Machine Mode)……………..…….200V PACKAGE/ORDER INFORMATION Order Part Number Package Top Marking MT3608 SOT23-6 A28YNN TOP VIEW SW 1 6 NC GND 2 5 VIN FB 3 4 EN 6-LEAD PLASTIC SOT-23 TJMAX = 160°C, θJA = 250°C/ W, θJC = 130°C/W Y:Year, NN: Internal Code PIN DESCRIPTION Pin Name Pin Number SW 1 GND 2 FB 3 EN 4 VIN NC 5 6 MT3608 Rev 3.1 Description Power Switch Output. SW is the drain of the internal MOSFET switch. Connect the power inductor and output rectifier to SW. Ground Pin Feedback Input. The FB voltage is 0.6V. Connect a resistor divider to FB. Regulator On/Off Control Input. A high input at EN turns on the converter, and a low input turns it off. When not used, connect EN to the input supply for automatic startup. Input Supply Pin. Must be locally bypassed. No Connect www.aerosemi.com Aerosemi Proprietary Information.Unauthorized Photocopy and Duplication Prohibited. All Rights Reserved. 2 MT3608 ELECTRICAL CHARACTERISTICS (Note 3) (VIN=VEN=5V,TA = 25°C, unless otherwise noted.) PARAMETER CONDITIONS Operating Input Voltage Under Voltage Lockout Under Voltage Lockout Hysteresis Current (Shutdown) VEN= 0V Quiescent Current VFB=0.7V，No switch (PFM) Quiescent Current VFB=0.5V，switch (PWM) Switching Frequency Maximum Duty Cycle VFB = 0V EN Input High Voltage EN Input Low Voltage FB Voltage SW On Resistance SW Current Limit VIN= 5V, Duty cycle=50% SW Leakage VSW = 20V Thermal Shutdown MIN 2.5 TYP MAX 24 2.4 100 mV 0.1 1 µA 70 150 µA 1.0 2.0 mA 0.4 0.612 150 MHz % V V V mΩ A μA ℃ 1.2 90 1.5 0.588 UNIT V V 0.6 80 4 1 155 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 (250°C/W). Note 3: 100% production test at 25°C. Specifications over the temperature range are guaranteed by design and characterization. MT3608 Rev 3.1 www.aerosemi.com Aerosemi Proprietary Information.Unauthorized Photocopy and Duplication Prohibited. All Rights Reserved. 3 MT3608 TYPICAL PERFORMANCE CHARACTERISTICS Efficiency vs. Load Current VOUT=5V 100 95 95 90 90 Efficiency(%) Efficiency(%) 100 85 VIN=3V 80 85 70 200 400 VIN=12V 75 VIN=4.2V 0 VIN=5V 80 VIN=3.7V 75 Efficiency vs. Load Current VOUT=18V 600 800 VIN=16V 70 1000 0 100 Load Current(mA) Line/Load Regulation VOUT=5V 5 400 500 VIN=3V 18 VIN=5V VIN=3.7V VIN=12V VIN=4.2V VIN=16V 4.5 17 0 200 400 600 800 1000 0 100 Load Current(mA) 200 300 400 500 Load Current(mA) Operation Frequency vs. Input Voltage VOUT=5V 1.3 Operation Frequency vs. Input Voltage VOUT=18V 1.3 1.2 Frequency(MHz) 1.2 Frequency(MHz) 300 Line/Load Regulation VOUT=18V 19 Output Voltage(V) Output Voltage(V) 5.5 200 Load Current(mA) 1.1 1 1.1 1 0.9 0.9 3 3.2 3.4 3.6 3.8 Input Voltage(V) MT3608 Rev 3.1 4 4.2 4 6 8 10 12 14 16 Input Voltage(V) www.aerosemi.com Aerosemi Proprietary Information.Unauthorized Photocopy and Duplication Prohibited. All Rights Reserved. 4 MT3608 FUNCTIONAL BLOCK DIAGRAM EN SW Shutdown Circuitry FB Error Amplifier PWM Compartor + M1 Control Logic + VREF Current Sense Compartor + + VIN UVLO OSC GND Figure 2. MT3608 Block Diagram FUNCTIONAL DESCRIPTION The MT3608 uses a fixed frequency, peak current mode boost regulator architecture to regulate voltage at the feedback pin. The operation of the MT3608 can be understood by referring to the block diagram of Figure 2. At the start of each oscillator cycle the MOSFET is turned on through the control circuitry. To prevent sub-harmonic oscillations at duty cycles greater 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 the PWM comparator. When this voltage equals The output voltage of the error amplifier the power MOSFET is MT3608 Rev 3.1 turned off. The voltage at the output of the error amplifier is an amplified version of the difference between the 0.6V bandgap reference voltage and the feedback voltage. In this way the peak current level keeps the output in regulation. If the feedback voltage starts to drop, the output of the error amplifier increases. These results in more current to flow through the power MOSFET, thus increasing the power delivered to the output. The MT3608 has internal soft start to limit the amount of input current at startup and to also limit the amount of overshoot on the output. www.aerosemi.com Aerosemi Proprietary Information.Unauthorized Photocopy and Duplication Prohibited. All Rights Reserved. 5 MT3608 APPLICATIONS INFORMATION Setting the Output Voltage The internal reference VREF is 0.6V (Typical).The output voltage is divided by a resistor divider,R1 and R2 to the FB pin. The output voltage is given by  R  VOUT = VREF   1 + 1   R2  Inductor Selection The recommended values of inductor are 4.7 to 22μH. Small size and better efficiency are the major concerns for portable device, such as MT3608 used for mobile phone. The inductor should have low core loss at 1.2MHz and low DCR for better efficiency. To avoid inductor saturation current rating should be considered. Capacitor Selection Input and output ceramic capacitors of 22μF are recommended for MT3608 applications. For better voltage filtering, ceramic capacitors with low ESR are recommended. X5R and X7R types are suitable because of their wider voltage and temperature ranges. Layout Consideration For best performance of the MT3608, the following guidelines must be strictly followed. ➢ Input and Output capacitors should be placed close to the IC and connected to ground plane to reduce noise coupling. ➢ The GND should be connected to a strong ground plane for heat sinking and noise protection. ➢ Keep the main current traces as possible as short and wide. ➢ SW node of DC-DC converter is with high frequency voltage swing. It should be kept at a small area. ➢ Place the feedback components as close as possible to the IC and keep away from the noisy devices. VOUT D VIN L COUT PIN1 GND MT3608(K) R2 VIA TO VOUT CIN R1 Diode Selection Schottky diode is a good choice for MT3608 because of its low forward voltage drop and fast reverses recovery. Using Schottky diode can get better efficiency. The high speed rectification is also a good characteristic of Schottky diode for high switching frequency. Current rating of the diode must meet the root mean square of the peak current and output average current multiplication as following Red Trace should be as short as possible Figure 3. MT3608 Suggested Layout ID (RMS)  IOUT  IPEAK The diode’ s reverse breakdown voltage should be larger than the output voltage. MT3608 Rev 3.1 www.aerosemi.com Aerosemi Proprietary Information.Unauthorized Photocopy and Duplication Prohibited. All Rights Reserved. 6 MT3608 PACKAGE DESCRIPTION SOT23-6 2.80 3.00 0.95 BSC 0.60 TYP 1.20 TYP EXAMPLE TOP MARK AAAA . 1.50 1.70 2.60 TYP 2.60 3.00 PIN 1 TOP VIEW RECOMMENDED SOLDER PAD LAYOUT GAUGE PLANE 0.25 BSC 0.90 1.30 1.45 MAX SEATING PLANE 0.30 0.50 0.95 BSC 0.00 0.15 FRONT VIEW 0°~8° 0.30 0.55 0.09 0.20 SIDE VIEW NOTE: 1.DIMENSIONS ARE IN MILLIMETERS. 2.DRAWING NOT TO SCALE. 3.DIMENSIONS ARE INCLUSIVE OF PLATING. 4.DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR. MT3608 Rev 3.1 www.aerosemi.com Aerosemi Proprietary Information.Unauthorized Photocopy and Duplication Prohibited. All Rights Reserved. 7 MT3608 IMPORTANT NOTICE Xi’an Aerosemi Technology Co.,Ltd reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services. Xi’an Aerosemi Technology Co.,Ltd is not responsible or liable for such altered documentation. Information of third parties may be subject to additional restrictions. Xi’an Aerosemi Technology Co.,Ltd does not assume any responsibility for use of any its products for any particular purpose, nor does Xi’an Aerosemi Technology Co.,Ltd assume any liability arising out of the application or use of any its products or circuits. Copyright © 2011, Xi’an Aerosemi Technology Co.,Ltd Http://www.aerosemi.com MT3608 Rev 3.1 www.aerosemi.com Aerosemi Proprietary Information.Unauthorized Photocopy and Duplication Prohibited. All Rights Reserved. 8