PWM CONTROL 3A STEP-DOWN CONVERTER FSP3131 FEATURES z z z z z z z z 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. TYPICAL APPLICATION z z z z z z z z z z 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 FSP3131 consists of step-down switching regulator with PWM control. These devices include a reference voltage source, oscillation circuit, error amplifier and internal PMOS. FSP3131 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 30KHz. 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. OUTPUT 5 OUTPUT PIN DESCRIPTION Pin Number Pin Name 1/7 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 2007-6-6 PWM CONTROL 3A STEP-DOWN CONVERTER FSP3131 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= 25°C, 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 2/7 ISSS Test Conditions Min. IIOUT= 0.1A IIOUT= 0.1A 0.784 VEN = 0 Measure waveform at SW pin 10 VSH Evaluate oscillation at SW pin Evaluate oscillation stop at SW pin 2.0 OCSET Pin Bias Current IOCSET Soft-Start Time TSS Internal MOSFET Rdson Rdson Efficiency EFFI Thermal Resistance Junction to Ambient θJA 23 V 0.8 0.816 V 0.1 0.5 µA A 10 fosc1 ISH ISL Unit 3.5 240 Enable Pin Input Leakage Current Max. 3.6 ΔVOUT /VOUT VIN =5V~23V, IIOUT= 0.2A IIOUT= 0.1A~3A ΔVOUT /VOUT Measure waveform at SW pin fosc VSL Typ. VIN =5V, VFB = 0 VIN =12V, VFB = 0 VIN =12V, VOUT =5V, IIOUT= 3A 1 0.2 300 µA 2 0.5 360 % % KHz KHz 0.8 V 75 20 -10 90 105 µA 0.3 2 5 ms 110 70 150 100 mΩ µA 91 % 65 °C/W 2007-6-6 PWM CONTROL 3A STEP-DOWN CONVERTER FSP3131 FUNCTIONAL BLOCK DIAGRAM FUNCTIONAL DESCROPTION PWM Control The FSP3131 consists of DC/DC converters that employ a pulse-width modulation (PWM) system. In converters of the FSP3131, 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 FSP3131 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 LOAD ×= R DS(ON) I OCSET × R OCSET See above formula for setting the current limit value 3/7 2007-6-6 PWM CONTROL 3A STEP-DOWN CONVERTER FSP3131 TYPICAL APPLICATION CIRCUIT Note: VOUT=VFB*(1+RA/RB) RB=0.7KΩ~5KΩ 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 2007-6-6 PWM CONTROL 3A STEP-DOWN CONVERTER FSP3131 TYPICAL CHARACTERISTICS 5/7 2007-6-6 PWM CONTROL 3A STEP-DOWN CONVERTER FSP3131 TYPICAL CHARACTERISTICS (CONTINUED) ORDER INFORMATION FSP3131XXXX Package: S: SOP8L Output Voltage: Blank: ADJ Temperature Grade: Packing: Blank: Tube or Bulk G: -20~125℃ A: Tape & Reel MARKING INFORMATION Logo FSP3131 Part number: YYWWXX Internal code Date code: YY: Year (01=2001) WW: Nth week (01~52) 6/7 2007-6-6 PWM CONTROL 3A STEP-DOWN CONVERTER FSP3131 θ H PACKAGE INFORMATION E D 7ο(4х) e B A 0.015х45ο A1 A2 7ο(4х) VIEW “A” Symbol A A1 A2 B C D E e H L θ 7/7 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 0ο 8ο Min. 1.40 0.10 1.30 0.33 0.19 4.80 3.70 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 0ο 2007-6-6 Max. 0.069 0.010 0.059 0.020 0.010 0.209 0.161 0.244 0.050 8ο