AX5201ESA

AX5201 Step-up PWM DC/DC Converter  GENERAL DESCRIPTION The AX5201 is high efficient step-up DC/DC converter. Large output current is possible having a built in internal N channel MOSFET, and using an external coil and diode. The AX5201 can be operated at switching frequencies of 500 kHz allowing for easy filtering and low noise, the size of the external components can be reduced. Output voltage is programmable with 1.0V of standard voltage supply internal, and using externally connected components, output voltage (FB) can be set up at will. The soft-start time can be programmed by outside capacitor; the function prevents overshoot at startup. Build inside Current limit, Thermal Shutdown and enable functions.  FEATURES - Input voltage：3V to 20V - Output voltage：3.3V to 32V - Duty ratio：0% to 85% PWM control - Oscillation frequency：500KHz. - Enable and Thermal Shutdown function. Internal Current limit. Built-in N-channel MOSFET SOP-8L with Exposed pad Pb-Free package.  BLOCK DIAGRAM Vcc Phase Compensation FB Regulator SW + + Buffer Driver Vref=1.0V PWM Controller EN VEN 8uA SS Oscillator Thermal Shutdown 0.06V SGND PGND 1/10 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Jan.25, 2011 AX5201  PIN ASSIGNMET The package of AX5201 is SOP-8L-EP; the pin assignment is given by: Name ( Top View ) EN 1 VCC 2 FB 3 SS 4 SGND Signal Ground pin. Exposed pad 8 SGND 7 PGND 6 SW 5 SW SOP-8L-EP (EP is connect to SW) PGND Power Ground pin Power-off pin H：normal operation(Step-up) EN L：Step-up operation stopped VCC IC power supply pin FB Feedback pin Switch pin. Connect inductor and diode here. Soft-Start Pin. SW SS  Description external ORDER/MARKING INFORMATION Order Information AX5201 XX X Package Type ES: SOP-8L-EP Top Marking Logo 2 01 AXY Y5 WW X Part number ID code:internal Packing Blank : Tube A : Taping WW: 01~52 Year: 10=2010 11=2011  ABSOLUTE MAXIMUM RATINGS (at TA=25°C) Characteristics Symbol Rating Unit VCC Pin Voltage VCC GND - 0.3 to GND + 22 V Feedback Pin Voltage VFB GND - 0.3 to 6 V ON/OFF Pin Voltage VEN GND - 0.3 to VCC V Switch Pin Voltage VSW GND - 0.3 to 34 V SS Pin Voltage VSS GND - 0.3 to 6 V Power Dissipation PD Internally limited mW Storage Temperature Range TST -40 to +150 °C Operating Junction Temperature TOPJ -20 to +125 °C Thermal Resistance from Junction to case θJC 15 °C/W Thermal Resistance from Junction to ambient θJA 40 °C/W Note : θJA is measured with the PCB copper area (connect to exposed pad) of approximately 1 in2(Multi-layer). 2/10 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Jan.25, 2011 AX5201  ELECTRICAL CHARACTERISTICS (VCC = 5V, VOUT=12V, TA=25°C, unless otherwise specified) Characteristics Symbol Conditions Min Typ Max Units Operating Supply Voltage VCC 3 - 20 V Output Voltage Range VOUT 3.3 - 32 V Feedback Voltage VFB IOUT=0.1A Feedback Bias Current Quiescent Current Shutdown Supply Current IFB ICCQ ISD IOUT=0.1A VFB=1.5V force driver off VEN =0V Oscillation Frequency FOSC SW pin 0.98 1.00 1.02 - 0.1 0.5 4 6 1 10 V uA mA uA 400 500 600 KHz Line Regulation VCC =3~0.8*VOUT - 1 - % Load Regulation - 1 - % VSH IOUT=50m~1A High (regulator ON) 2.0 - - VSL Low (regulator OFF) - - 0.8 ISH VEN=2.5V (ON) - 20 - uA ISL VEN=0.3V (OFF) - -1 - uA - 8 - uA - A EN Pin Logic input threshold voltage EN Pin Input Current SS pin Current ISS Switching Current Limit ILIM-sw Internal MOSFET RDSON RDSON Efficiency EFFI Maximum Duty Cycle Minimum Duty Cycle Thermal shutdown Temp 2.8 3.0 VCC=5V - 40 80 VCC=12V - 30 60 - 92 - DCMAX VFB=0V - 85 - DCMIN VFB=1.5V - 0 - - 145 - TSD VCC=5V VOUT=12V IOUT = 0.5A V mΩ % % °C 3/10 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Jan.25, 2011 AX5201  APPLICATION CIRCUIT VCC=5V L1 22uH Vout=12V D1 B340A U1 1 R1 100K 2 3 4 C1 C7 470uF 0.1uF C3 Option EN SGND Vcc PGND FB SS AX5201 SW SW 8 7 6 C4 C5 5 470uF 4.7uF R4 11K C8 0.47uF C2 0.47uF R3 1K VOUT = VFB  (1 + R4 ), VFB = 1.0V, R3 = 1K ~ 3KΩ R3  FUNCTION DESCRIPTIONS PWM Control The AX5201 consists of DC/DC converters that employ a pulse-width modulation (PWM) system. In converters of the AX5201, the pulse width varies in a range from 0 to 85%, according to the load current. The ripple voltage produced by the switching can easily be removed through a filter because the switching frequency remains constant. Therefore, these converters provide a low-ripple power over broad ranges of input voltage and load current. Setting the Output Voltage Application circuit item shows the basic application circuit with AX5201 adjustable output version. The external resistor sets the output voltage according to the following equation: V OUT R4    1.0V  1   R3   4/10 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Jan.25, 2011 AX5201 Table 1 Resistor select for output voltage setting VOUT R3 R4 12V 1K 11K 15V 1.3K 18K 18V 1.3K 22K 24V 1.3K 30K 32V 2.2K 68K Inductor Selection For most designs, Low inductance values are physically smaller but require faster switching, which results in some efficiency loss. The inductor value can be derived from the following equation: L  V IN V  V OUT  V IN  OUT  I L  f LX Where is inductor Ripple Current. Large value inductors lower ripple current and small value inductors result in high ripple currents. Choose inductor ripple current approximately 15% of the maximum input current 2.4A, ΔIL=0.18A. Table 2 Inductor select for output voltage setting (VCC=5V) VOUT 9V 12V 15V 18V L1 Value 18uH 22uH 25uH 33uH 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 (2.4A+0.18A). Input Capacitor Selection 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. A low ESR input capacitor sized for maximum RMS current must be used. The capacitor voltage rating should be at least 1.5 times greater than the input voltage, and often much higher voltage ratings are needed to satisfy. 5/10 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Jan.25, 2011 AX5201 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 frequency. A low ESR capacitor sized for maximum RMS current must be used. The low ESR requirements needed for low output ripple voltage. The capacitor voltage rating should be at least 1.5 times greater than the input voltage, and often much higher voltage ratings are needed to satisfy. Output Voltage Ripple Application circuit item shows the basic application circuit with AX5201. The output voltage ripple (VRIPPLE) very lager at high switch current(ISW=3A, VRIPPLE≒0.7V), external π filters can reduce output voltage ripple. π filters VCC=5V VOUT=12V L1 R1 22uH D1 B340A L2 2.2uH U1 100K C1 C7 EN SGND C4 C5 R4 C9 C10 470uF 0.1uF VCC PGND 470uF 4.7uF 11K 330uF 0.1uF C3 Option C8 FB SW SS SW AX5201 0.47uF R3 1K 6/10 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Jan.25, 2011 AX5201 Layout Guidance (please refer layout picture) When laying out the PC board, the following suggestions should be taken to ensure proper operation of the AX5201. These items are also illustrated graphically in below. 1. The power traces, including the Source trace, the Schottky and the C1 trace should be kept short, direct and wide to allow large current flow. 2. The power ground is keep C4’s ground closed and far away signal ground. 3. The signal ground trance is distant from power ground trance. 4. The exposed pad is connecting to SW trace closely and widely. (Reduce IC temperature) 5. Do not trace signal line under inductor. (AX5201 PCB Layout -Top View) 7/10 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Jan.25, 2011 AX5201  TYPICAL CHARACTERISTICS IOUT VS VOUT Vout (V) Vout (V) VCC VS VOUT 13 12.8 12.6 12.4 12.2 12 11.8 11.6 11.4 11.2 11 IOUT=0.1A 3 4 5 6 7 8 9 13 12.8 12.6 12.4 12.2 12 11.8 11.6 11.4 11.2 11 VCC=5V 0 10 100 400 500 600 Temperature VS Curret Limit 6.0 5.0 Current Limit (A) Current Limit (A) VCC VS Current Limit 4.0 3.0 2.0 1.0 VOUT=24V VCC=5V, Vout=12V 0.0 3 6 9 12 15 18 -50 -25 VCC (V) 0 25 50 Temperature (℃) 75 100 75 100 Temperature VS VFB Temperature VS Frequency 750 1.05 700 1.04 1.03 650 600 VFB (V) Frequency (KHz) 300 IOUT (mA) VCC (V) 6 5.5 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 200 550 500 450 1.02 1.01 1.00 0.99 0.98 400 350 0.97 0.96 VCC=5V, Vout=12V IOUT=100mA 300 250 0.95 -50 -25 0 25 50 Temperature (℃) 75 100 -50 -25 0 25 50 Temperature (℃) 8/10 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Jan.25, 2011 AX5201  TYPICAL CHARACTERISTICS (CONTINUOUS) Power-ON Wave Enable-ON Wave (VCC=5V, VOUT=12V, Load=0.8A, SS=0.47uF) (VCC=5V, VOUT=12V, Load=0.8A, SS=0.47uF) 9/10 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Jan.25, 2011 AX5201  PACKAGE OUTLINES H E Expose Pad Y X θ L DETAIL A b D e y A1 C A A2 7 (4X) Dimensions in Millimeters Min. Nom. Max. A 1.75 A1 0 0.15 A2 1.25 C 0.1 0.2 0.25 D 4.7 4.9 5.1 E 3.7 3.9 4.1 H 5.8 6 6.2 L 0.4 1.27 b 0.31 0.41 0.51 e 1.27 BSC y 0.1 X 2.34 Y 2.34 O θ 0 8O Mold flash shall not exceed 0.25mm per side JEDEC outline: MS-012 BA Symbol DETAIL A Dimensions in Inches Min. Nom. Max. 0.069 0 0.06 0.049 0.0075 0.008 0.01 0.185 0.193 0.2 0.146 0.154 0.161 0.228 0.236 0.244 0.015 0.05 0.012 0.016 0.02 0.050 BSC 0.004 0.092 0.092 O 0 8O 10/10 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.4 Jan.25, 2011