Liteon Semiconductor Corporation LSP3131 PWM Control 3A Step-Down Converter FEATURES GENERAL DESCRIPTION Input voltage: 3.6V to 23V. Output voltage: 0.8V to VCC. Duty ratio: 0% to 100% PWM control Oscillation frequency: 300KHz typ. Soft-start, Current limit, Enable function Thermal Shutdown function Built-in internal SW P-channel MOSFET SOP8L Package. LSP3131 consists of step-down switching regulator with PWM control. These devices include a reference voltage source, oscillation circuit, error amplifier and internal PMOS. LSP3131 provides low-ripple power, high efficiency, and excellent transient characteristics. The PWM control circuit is able to vary the duty ratio linearly from 0 up to 100%. This converter also contains an error amplifier circuit as well as a soft-start circuir that prevents overshoot at startup. An enable function, an over current protect function and a short circuit protect function are built inside, and when OCP or SCP happens, the operation frequency will be reduced from 300KHz to 50KHz. Also, an internal compensation block is built in to minimum external component count. With the addition of an internal P-channel Power MOS, a coil, capacitors, and a diode connected externally, these ICs can function as step-down switching regulators. They serve as ideal power supply units for portable devices when coupled with the SOP8L mini-package, providing such outstanding features as low current consumption. Since this converter can accommodate an input voltage up to 23V, it is also suitable for the operation via an AC adapter. TYPICAL APPLICATION Cellular Phones PC Motherboard LCD Monitor Graphic Card DVD-Video Player Telecom Equipment ADSL Modem Printer and other Peripheral Equipment Microprocessor core supply Networking power supply PIN ASSIGNMENT (Top View) FB 1 8 VSS EN 2 7 VSS OCSET 3 6 VCC 4 OUTPUT 5 OUTPUT PIN DESCRIPTION Pin Number Pin Name Pin Description 1 FB Feedback Pin 2 EN Enable Input Pin H: Normal operation(Step-down operation) L: Step-down operation stopped(All circuits deactivated) 3 OCSET 4 VCC 5,6 OUTPUT 7,8 VSS Add an external resistor to set max output current IC power supply pin Switch pin. Connect external inductor/diode here. Minimize trace area at this pin to reduce EMI. GND pin 1/7 Rev1.0 Liteon Semiconductor Corporation LSP3131 PWM Control 3A Step-Down Converter ABSOLUTE MAXIMUM RATINGS(NOTE) Parameter VCC Pin Voltage, VCC Value VSS-0.3 to VSS+25 Unit V Feedback Pin Voltage, VFB VSS-0.3 to VCC V EN Pin Voltage, VEN Switch Pin Voltage, VOUTPUT Power Dissipation, PD VSS-0.3 to VIN + 0.3 VSS-0.3 to VIN + 0.3 Internally limited V V mW Operating Temperature Range, TOPR -20 to +125 C Storage Temperature Range, TSTG -40 to +150 C Note: Do not exceed these limits to prevent damage to the device. Exposure to absolute maximum rating conditions for long periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VIN = 12V, TA= 25C, unless otherwise specified.) Parameter Symbol Input Voltage VIN Feedback Voltage VFB Feedback Bias Current Switch Current Current Consumption During Power Off Line Regulation Load Regulation Oscillation Frequency Frequency of Current Limit or Short Circuit Protect IFB ISW Enable Pin Input Voltage Test Conditions IIOUT= 0.1A IIOUT= 0.1A VSH OCSET Pin Bias Current IOCSET Soft-Start Time TSS Internal MOSFET Rdson Rdson Efficiency EFFI 0.784 VEN = 0 fosc1 ISH ISL Max. Unit 23 V 0.8 0.816 V 0.1 0.5 A A 3.5 VOUT /VOUT VIN =5V~23V, IIOUT= 0.2A IIOUT= 0.1A~3A VOUT /VOUT Measure waveform at SW pin fosc Enable Pin Input Leakage Current Typ. 3.6 ISSS VSL Min. 10 A 240 1 0.2 300 2 0.5 360 % % KHz Measure waveform at SW pin 30 50 70 KHz Evaluate oscillation at SW pin Evaluate oscillation stop at SW pin 2.0 VIN =5V, VFB = 0 VIN =12V, VFB = 0 VIN =12V, VOUT =5V, IIOUT= 3A 0.8 V 75 20 -10 90 105 A 0.3 2 5 ms 80 50 90 65 m A 91 % JA 65 C/W JC 20 C/W Over temperature shutdown TSD 150 C Over temperature shutdown Hysteresis THYS 25 C Thermal Resistance Junction to Ambient Thermal Resistance Junction to Case 2/7 Rev1.0 Liteon Semiconductor Corporation LSP3131 PWM Control 3A Step-Down Converter FUNCTIONAL BLOCK DIAGRAM FUNCTIONAL DESCROPTION PWM Control The LSP3131 consists of DC/DC converters that employ a pulse-width modulation (PWM) system. In converters of the LSP3131, the pulse width varies in a range from 0 to 100%, 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. Under Voltage Lockout The under voltage lockout circuit of the LSP3131 assures that the high-side MOSFET driver outputs remain in the off state whenever the supply voltage drops below 3.3V. Normal operation resumes once VCC rises above 3.5V. RDS(ON) Current Limiting The current limit threshold is setting by the external resistor connecting from VCC supply to OCSET. The internal 100uA sink current crossing the resistor sets the voltage at the pin of OCSET. When the PWM voltage is less than the voltage at OCSET, an over-current condition is triggered. I PEAK xR DS(ON) =I OCSET x R OCSET See above formula for setting the current limit value 3/7 Rev1.0 Liteon Semiconductor Corporation LSP3131 PWM Control 3A Step-Down Converter TYPICAL APPLICATION CIRCUIT Note1:CIN/COUT can be Electro capacitor or Tan capacitor; The typical CIN Electro capacitor is 470uF/35V,the typical CIN Tan capacitor is 100uF/35V; The typical COUT Electro capacitor is 470uF/16V,the typical COUT Tan capacitor is 22uF/16V; Note2: VOUT=VFB*(1+RA/RB) RB=0.7K~5K VIN=12V, IMAX=3A VOUT L1 Value 2.5V 15uH 3.3V 18uH 5V 22uH TEST CIRCUITS 1) Enable Function Test 2) Feedback Function Test 3) Operation Function Test 4/7 Rev1.0 Liteon Semiconductor Corporation LSP3131 PWM Control 3A Step-Down Converter TYPICAL CHARACTERISTICS 5/7 Rev1.0 Liteon Semiconductor Corporation LSP3131 PWM Control 3A Step-Down Converter TYPICAL CHARACTERISTICS (CONTINUED) ORDERING INFORMATION MARKING INFORMATION 6/7 Rev1.0 Liteon Semiconductor Corporation LSP3131 PWM Control 3A Step-Down Converter H L E PACKAGE INFORMATION VIEW "A" D 7(4) B Symbol A A1 A2 B C D E e H L A C e 0.015 45 A1 A2 7 (4) Dimensions In Millimeters Nom. Max. 1.60 1.75 0.25 1.45 1.50 0.41 0.51 0.20 0.25 5.05 5.30 3.90 4.10 1.27TYP. 5.80 5.99 6.20 0.38 0.71 1.27 0 8 Min. 1.40 0.10 1.30 0.33 0.19 4.80 3.70 7/7 VIEW "A" Dimensions In Inches Min. Nom. 0.055 0.063 0..004 0.051 0.057 0.013 0.016 0.0075 0.008 0.189 0.199 0.146 0.154 0.050TYP. 0.228 0.236 0.015 0.028 0 Max. 0.069 0.010 0.059 0.020 0.010 0.209 0.161 0.244 0.050 8 Rev1.0