AX5523CA

AX5523 High Efficiency 1.2MHz 2A Step Up Converter  GENERAL DESCRIPTION The AX5523 is a constant frequency, 6-pin SOT23 current mode step-up converter intended for small, low power applications. The AX5523 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 AX5523 features automatic shifting to pulse frequency modulation mode at light loads. The AX5523 includes under-voltage lockout, current limiting, and thermal overload protection to prevent damage in the event of an output overload. The AX5523 is available in a small 6-pin SOT-23 package.  FEATURES - Integrated 80mΩ Power MOSFET 2.6V to 12V 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 97% Efficiency Available in a 6-Pin SOT23-6 package 1/9 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Nov.24, 2015 AX5523  BLOCK DIAGRAM  PIN ASSIGNMENT The package of AX5523 is SOT-23-6L; the pin assignment is given by: Name SW NC VIN EN 6 5 4 ( Top View) SOT-23-6L 1 2 3 SW GND FB GND FB EN VIN NC Description Power Switch Output. SW is the drain of the internal MOSFET switch. Connect the power inductor and output rectifier to SW. SW can swing between GND and 28V. Analog 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. NC 2/9 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Nov.24, 2015 AX5523  ORDER/MARKING INFORMATION Order Information W 2Y WX AX5523 XX X Package Type C: SOT23-6L Top Marking Packing Blank : Tube A : Taping WW:01~26 (A~Z) 27~52 (a~z) Year: 2=2012 3=2013 : : 9=2019 AX5523  ABSOLUTE MAXIMUM RATINGS Characteristics IN, EN voltages SW Voltage Operating Temperature Storage Temperature Range FB Voltages Peak SW Sink and Source Current Junction Temperature Lead Temperature (Soldering, 10s) Rating -0.3 to 12 -0.3 to 30 -40 to +85 -65 to +150 -0.3 to 6 4 130 250  ELECTRICAL CHARACTERISTICS (VIN=VEN=5V, TA = 25°C, unless otherwise noted.) Characteristics Conditions Operating Input Voltage Under Voltage Lockout Under Voltage Lockout Hysteresis Shutdown Current Quiescent Current Switching Frequency Maximum Duty Cycle EN Input High Voltage VEN= 0V VFB=0.7V，No switch VFB = 0V EN Input Low Voltage FB Voltage FB Input Bias Current SW On Resistance (1) SW Current Limit (1) SW Leakage Thermal Shutdown ID code:internal VFB = 0.6V VIN= 5V, Duty cycle=50% VSW = 20V Unit V V °C °C V A °C °C Min Typ Max Units 2.6 12 V 2.6 V - 100 mV 0.1 1 µA - 100 200 µA 0.8 1.2 1.6 MHz 90 % 1.5 V 0.4 V 0.588 0.6 0.612 V -50 -10 nA 80 150 mΩ 3 4 A 1 μA - 155 °C Note: Guaranteed by design, not tested. 3/9 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Nov.24, 2015 AX5523  APPLICATION CIRCUIT L1 4.7uH D1 VCC (3V~16V) VOUT < 28V R3 100KΩ C1 22uF VIN SW R1 EN GND FB AX5523 C2 22uF R2 Basic Application Circuit  FUNCTION DESCRIPTION The AX5523 uses a fixed frequency, peak current mode boost regulator architecture to regulate voltage at the feedback pin. The operation of the AX5523 can be understood by referring to the block diagram of Block Diagram item. 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 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 AX5523 has internal soft start to limit the amount of input current at startup and to also limit the amount of overshoot on the output. 4/9 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Nov.24, 2015 AX5523  APPLICATION 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 4.7μH to 22μH. Small size and better efficiency are the major concerns for portable device, such as AX5523 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 AX5523 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. Diode Selection Schottky diode is a good choice for AX5523 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: I D ( RMS )  I OUT  I PEAK The diode’s reverse breakdown voltage should be larger than the output voltage. 5/9 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Nov.24, 2015 AX5523 PCB Layout Recommendations When laying out the printed circuit board, the following checking should be used to ensure proper operation of the AX5523. Check the following in your layout: 1. The power traces, consisting of the GND trace, the SW trace and the V IN trace should be kept short, direct and wide. 2. Does the (+) plates of CIN connect to VIN as closely as possible. This capacitor provides the AC current to the internal power MOSFETs. 3. Keep the switching node SW away from the sensitive V OUT node. 4. Keep the (-) plates of CIN and COUT as close as possible. R3 VIN C1 NC VIN EN 6 5 4 1 2 3 SW GND FB AX5523 L1 D1 C2 R2 GND VOUT R1 6/9 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Nov.24, 2015 AX5523  TYPICAL CHARACTERISTICS (CONTINUOUS) 7/9 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Nov.24, 2015 AX5523  TYPICAL CHARACTERISTICS (CONTINUOUS) 8/9 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Nov.24, 2015 AX5523  PACKAGE OUTLINES D E E1 C GAUGE PLANE L θ L1 e DETAL A A1 A A2 e1 DETAL A b Dimensions in Millimeters Min. Nom. Max. A 1.45 A1 0.00 0.15 A2 0.90 1.10 1.30 b 0.30 0.40 0.50 C 0.08 0.22 D 2.70 2.90 3.10 E1 1.40 1.60 1.80 E 2.60 2.80 3.00 L 0.30 0.45 0.60 L1 0.50 0.60 0.70 e1 1.9 BSC e 0.95 BSC θ 0o 4o 8o JEDEC outline: MO-178 AB Symbol Dimensions in Inches Min. Nom. Max. 0.057 0 0.003 0.006 0.035 0.043 0.051 0.012 0.016 0.020 0.003 0.006 0.009 0.106 0.114 0.122 0.055 0.063 0.071 0.102 0.110 0.118 0.012 0.018 0.024 0.020 0.024 0.028 0.075 BSC 0.037 BSC 0o 4o 8o 9/9 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Nov.24, 2015