150KHZ，2A PWM BUCK DC/DC CONVERTER FSP3125 FEATURES z Output voltage: 3.3V, 5V, 12V and adjustable output version z Adjustable version output voltage range, 1.23V to 18V ± 4% z 150KHz ±15% fixed switching frequency z Voltage mode non-synchronous PWM control z Thermal-shutdown and current-limit protection z ON/OFF shutdown control input z Operating voltage can be up to 22V z Output load current: 2A z SOP8L packages z Low power standby mode z Built-in switching transistor on chip Typical Application z z z Simple High-efficiency step-down regulator On-card switching regulators Positive to negative converter GENERAL DESCRIPTION The FSP3125 series are monolithic IC designed for a step-down DC/DC converter, and own the ability of driving a 2A load without additional transistor. It saves board space. The external shutdown function can be controlled by logic level and then come into standby mode. The internal compensation makes feedback control having good line and load regulation without external design. Regarding protected function, thermal shutdown is to prevent over temperature operating from damage, and current limit is against over current operating of the output switch. If current limit function occurs and FB is down below 0.5V, the switching frequency will be reduced. The FSP3125 series operates at a switching frequency of 150KHz thus allow smaller sized filter components than what would be needed with lower frequency switching regulators. Other features include a guaranteed ± 4% tolerance on output voltage under specified input voltage and output load conditions, and ± 15% on the oscillator frequency. The output version included fixed 3.3V, 5V, 12V, and an adjustable type. The chips are available in a standard SOP8L package. PIN ASSIGNMENT (Top View) VIN 1 8 GND OUTPUT 2 FB 3 SD 4 7 GND FSP3125 6 GND 5 GND PIN DESCRIPTION Name VIN OUTPUT FB SD GND GND GND GND 1/9 No. 1 2 3 4 5 6 7 8 Description Operating Voltage Input Switching Output Output Voltage Feedback Control On/Off Shutdown Ground Ground Ground Ground 2007-3-27 150KHZ，2A PWM BUCK DC/DC CONVERTER FSP3125 ABSOLUTE MAXIMUM RATINGS Parameter Supply Voltage On/Off Pin Input Voltage Feedback Pin Voltage Output Voltage to Ground Power Dissipation Storage Temperature Operating Temperature Operating Voltage Value +24 -0.3 to +18 -0.3 to +18 -1 Internally Limited -65 to +150 -40 to +125 +4.5 to +22 Unit V V V V W ℃ ℃ V ELECTRICAL CHARACTERISTICS (Unless otherwise specified, VIN=12V for 3.3V, 5V and adjustable version and VIN=18V for the 12V version. ILOAD = 0.5A) Parameter Symbol Feedback Bias Current IFB Oscillator Frequency Fosc Short Circuit Oscillator Frequency FCSP Saturation Voltage VSAT Maximum Duty Cycle(On) Minimum Duty Cycle(Off) DC Current Limit ICL Output Leakage Current Output=-1 Quiescent Current IQ When Current Limit Occur and VFB ＜ 0.5V, TA=25°C IOUT= 2A, No Outside Circuit , VFB = 0V force drive on VFB = 0V force drive on VFB =12V force drive off Peak Current No Outside Circuit , VFB = 0V force drive on No Outside Circuit , VFB = 12V force drive off VIN = 22V VFB = 12V force drive off Standby Quiescent Current ISTBY ON/OFF Pin=5V,VIN = 22V ON/OFF Pin Logic Input Threshold Voltage ON/OFF Pin Input Current ON/OFF Pin Logic Input Current Thermal Resistance Thermal Resistance with Copper Area of Approximately 3 in2 VIL VIH IL Low (Regulator ON) High (Regulator OFF) VLOGIC=0.5V(ON) IH VLOGIC=2.5V(OFF) Output=0 2/9 Test Conditions VFB = 1.3V (Adjustable Version Only) IL Min. Typ. -10 127 110 150 10 30 1.25 Max. -50 -100 173 173 Unit 50 kHz 1.4 1.5 100 0 3.6 6.9 3.4 7.5 5 70 2.0 1.3 nA kHz V % A -50 µA -30 10 200 250 0.6 mA mA µA V -5 -15 θJC SOP8L Junction to Case 15 θJA SOP8L Junction to Ambient 70 2007-3-27 µA ℃/W 150KHZ，2A PWM BUCK DC/DC CONVERTER FSP3125 ELECTRICAL CHARACTERISTICS(CONTINUED) (Unless otherwise specified, VIN=12V for 3.3V, 5V and adjustable version and VIN=18V for the 12V version. ILOAD = 0.5A) Parameter Output Feedback Symbol VFB FSP3125-ADJ Test Conditions 4.5V ≤VIN ≤22V 0.2A ≤ILOAD ≤2A VOUT Programmed for 3V Min. 1.193 1.18 Efficiency η VIN =12V, ILOAD= 2A 75 Output Feedback VOUT 4.5V ≤VIN ≤22V 0.2A ≤ILOAD ≤2A 3.168 3.135 η VIN =12V, ILOAD= 2A 78 7V ≤VIN ≤22V 0.2A ≤ILOAD ≤2A VIN =12V, ILOAD= 2A 4.8 4.75 83 15V ≤VIN ≤22V 0.2A ≤ILOAD ≤2A 11.52 FSP3125-3.3V Efficiency Output Feedback Efficiency Output Feedback FSP3125-5.0V VOUT η FSP3125-12V VOUT Typ. 1.23 Max. 1.267 1.28 3/9 V % 3.3 3.432 3.465 V % 5.2 5.25 5 12 12.48 11.4 12.6 Efficiency η VIN =15V, ILOAD= 2A 90 Specifications with boldface are for full operating temperature range, the other type are for TJ=25°C Unit FUNCTIONAL BLOCK DIAGRAM 2007-3-27 V % V % 150KHZ，2A PWM BUCK DC/DC CONVERTER FSP3125 Function Description Pin Description +VIN This is the positive input supply for the IC switching regulator. A suitable input bypass capacitor must be presented at this pin to minimize voltage transients and to supply the switching currents needed by the regulator. Ground Circuit Ground Output Internal Switch. The voltage at this pin switches between (+VIN-VSAT) and approximately -0.5V, with a duty cycle of approximately VOUT/VIN. To minimize coupling to sensitive circuitry, the PC board copper area connected to this pin should be minimized. Feedback Sense the regulated output voltage to complete the feedback loop. SD Allows the switching regulator circuit to be shutdown using logic level signals thus dropping the total input supply current to approximately 150uA. Pulling this pin below a threshold voltage of approximately 1.3V turns the regulator on, and pulling this pin above 1.3V (up to a maximum of 18V) shuts the regulator down. If this shutdown feature is not needed, the SD pin can be wired to the ground pin. Thermal Considerations The SOP8L package needs a heat sink under most conditions. The size of the heatsink depends on the input voltage, the output voltage, the load current and the ambient temperature. The FSP3125 junction temperature rises above ambient temperature for a 2A load and different input and output voltages. The data for these curves was taken with the FSP3125(SOP8L package) operating as a buck-switching regulator in an ambient temperature 25℃ (still air). These temperature increments are all approximate and are affected by many factors. Higher ambient temperatures requires more heat sinker. For the best thermal performance, wide copper traces and generous amounts of printed circuit board copper should be used in the board layout. (One exception is the output (switch) pin, which should not have large areas of copper.) Large areas of copper provide the best transfer of heat (lower thermal resistance) to the surrounding air, and moving air lowers the thermal resistance even further. Package thermal resistance and junction temperature increments are all approximate. The increments are affected by a lot of factors. Some of these factors include board size, shape, thickness, position, location, and even board temperature. Other factors are, trace width, total printed circuit copper area, copper thickness, single or double-sided, multi-layer board and the amount of solder on the board. The effectiveness of the PC board to dissipate heat also depends on the size, quantity and spacing of other components on the board, as well as whether the surrounding air is still or moving. Furthermore, some of these components such as the catch diode will add heat to the PC board and the heat can vary as the input voltage changes. For the inductor, depending on the physical size, type of core material and the DC resistance, it could either act as a heat sink taking heat away from the board, or it could add heat to the board. 4/9 2007-3-27 150KHZ，2A PWM BUCK DC/DC CONVERTER FSP3125 Typical Application Circuit (1) Fixed Output Version Circuit (2) Adjustable Version Circuit 5/9 2007-3-27 150KHZ，2A PWM BUCK DC/DC CONVERTER FSP3125 TYPICAL CHARACTERISTICS 6/9 2007-3-27 150KHZ，2A PWM BUCK DC/DC CONVERTER FSP3125 TYPICAL CHARACTERISTICS(CONTINUED) 7/9 2007-3-27 150KHZ，2A PWM BUCK DC/DC CONVERTER FSP3125 ORDER INFORMATION FSP3125XXXX Package: S: SOP8L Temperature Grade: Output Voltage: Packing: Blank: Tube or Bulk E: -40~125℃ Blank: ADJ A: Tape & Reel 33: 3.3V 50: 5.0V 12: 12V MARKING INFORMATION Logo 3125-VV YYWWXX Part number: 3125-ADJ: ADJ 3125-33: 3.3V 3125-50: 5.0V 3125-12: 12V Internal code Date code: YY: Year (01=2001) WW: Nth week (01~52) 8/9 2007-3-27 150KHZ，2A PWM BUCK DC/DC CONVERTER FSP3125 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 9/9 Dimensions In Millimeters Nom. Max. 1.60 1.75 0.25 1.45 1.55 0.41 0.51 0.20 0.25 4.90 5.00 3.90 4.00 1.27TYP. 5.80 5.99 6.30 0.38 0.71 1.27 0ο 8ο Min. 1.35 0.10 1.35 0.33 0.19 4.80 3.80 Dimensions In Inches Min. Nom. 0.053 0.063 0..004 0.053 0.057 0.013 0.016 0.0075 0.008 0.192 0.196 0.148 0.154 0.050TYP. 0.228 0.236 0.015 0.028 0ο 2007-3-27 Max. 0.069 0.010 0.061 0.020 0.010 0.200 0.160 0.248 0.050 8ο