SE1482 SEAWARD | Alldatasheet
Document overview
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Technical content
Features
2A Output Current Wide 4.5V to 27V Operating Input Range Output Adjustable from 0.925V to 0.8Vin Up to 96% Efficiency Programmable Soft-Start Stable with Low ESR Ceramic Output Capacitors Fixed 340KHZ Frequency Cycle-by-Cycle Over Current Protection Short Circuit Protection Input Under Voltage Lockout Package： SOP-8/PSOP-8 Pin Configuration
Applications
Distributed Power Systems Green Electronics/ Appliances Notebook Computers Networking Systems FPGA, DSP, ASIC Power Supplies
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com .cn • Page 2 9/4/2012 SE1482 2A 27V Synchron ous Buck Converter Functional Block Diagram
Ordering Information
Part Number Marking Information Package Remarks SE1482-HF SE1482 YYWW-HF SOP8 YYWW means Production batch XX=HF: Halogen Free. PSOP8 Pin Descriptions Pin Num Pin Descriptions 1 BS Bootstrap. This pin acts as the positive rail for the high-side switch’s gate driver. Connect a 0.01uF capacitor between BS and SW.
2 Vin
Input Supply. Bypass this pin to GND with a low ESR capacitor. See Input Capacitor in the Application Information section. 3 SW Switch Output. Connect this pin to the switching end of the inductor. 4 GND Ground. 5 FB Feedback Input. The voltage at this pin is regulated to 0.925V. Connect to the resistor divider between output and ground to set output voltage. 6 COMP Compensation Pin. See Stability Compensation in the Application Information section. 7 EN Enable Input. When higher than 2.7V, this pin turns the IC on. When lower than 1.1V, this pin turns the IC off. Output voltage is discharged when the IC is off. This pin should not be left open. Recommend to put a 100KΩ pull up resistor to Vin for start up. 8 SS Soft-Start Control Input. SS controls the soft-start period. Connect a capacitor from SS to GND to set the soft-start period. A 0.1uF capacitor sets the soft-start period to 15ms. To disable the soft-start feature, leave SS unconnected.
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com .cn • Page 3 9/4/2012 SE1482 2A 27V Synchron ous Buck Converter Absolute Maximum Rating Parameter Maximum Units Input Supply Voltage -0.3 to 30 V SW Voltage -0.3 to VIN + 0.3 V BS Voltage VSW – 0.3 to VSW + 6 V EN, FB, COMP Voltage -0.3 to 5 V Continuous SW Current Internally limited A Junction to Ambient Thermal Resistance (θJA) 87 °C/W PSOP-8 Power Dissipation Internal limit W Maximum Junction Temperature 150 °C Storage Temperature Range -65 to 150 °C Note: Exceeding these limits may damage the device. Even the duration of exceeding is very short. Exposure to absolute maximum rating conditions for long periods may affect device reliability。 Recommended Operating Conditions Parameter Symbol Value Units Supply Input Voltage VIN 4.5 to +27 V Operating Junction Temperature TJ -20 to +125 °C
Electrical Characteristics
VIN = 12V; TJ = 25° C; unless otherwise specified Parameter Symbol Conditions Min Typ Max Unit Feedback Voltage VFB 4.5V ≤ VIN ≤ 27V 0.9 0.925 0.95 V Feedback Overvoltage Threshold 1.1 V High-Side Switch-On Resistance* mΩ Low-Side Switch-On Resistance* mΩ High-Side Switch Leakage VEN = VSW = 0V , 10 uA Upper Switch Current Limit* Min Duty Cycle 2.7 3.5 A COMP to Current Limit Trans conductance GCOMP 3.3 A/V Error Amplifier Trans conductance GEA ΔICOMP = ± 10uA 920 uA/V Error Amplifier DC Gain*A VEA 480 V/V Switching Frequency fSW 340 KHz Short Circuit Switching Frequency VFB = 0V 120 KHz Maximum Duty Cycle DMAX VFB = 0.8V Minimum On Time* 220 nS EN Shutdown Threshold Voltage VEN Rising 1.1 1.4 2 V EN Shutdown Threshold Voltage Hysteresis 180 mV
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com .cn • Page 4 9/4/2012 SE1482 2A 27V Synchron ous Buck Converter EN Lockout Threshold Voltage 2.2 2.5 2.7 V EN Lockout Hysteresis 130 mV Supply Current in Shutdown VEN = 0V 0.3 3 uA IC Supply Current in Operation VEN = 3V, VFB=1.0V 1.3 1.5 mA Input UVLO Threshold Rising UVLO VEN Rising 3.8 4.05 4.4 V Input UVLO Threshold Hysteresis 100 mV Soft-start Current VSS = 0V uA Soft-start Period CSS =0.1uF mS Thermal Shutdown Temperature* Hysteresis =25° C 160 Note: * Guaranteed by design, not tested Typical Application SE1482 Circuit, 3.3V/2A output SE1482 Circuit, 3.3V/2A output with EN function Note: C2 is required for separate EN signal.
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com .cn • Page 5 9/4/2012 SE1482 2A 27V Synchron ous Buck Converter select an inductance value。 L based on the ripple current requirement: Where VIN is the input voltage, VOUT is the output voltage, fSW is the switching frequency, IOUTMAX is the maximum output current, and KRIPPLE is the ripple factor. Typically, choose KRIPPLE =~ 30% to correspond to the peak -to-peak ripple current being ~30% of the maximum output current. With this inductor value, the peak inductor current is IOUT•(1+KRIPPLE/2). Make sure that this peak inductor current is less than the upper switch current limit. Finally, select the inductor core size so that it does not saturate at the current limit. Typical inductor values for various output voltages are shown in Table 2. Table 2. Typical Inductor Values resistors R1 and R2 based on the output voltage. low ESR Electrolytic (EC) capacitor is highly recommended. switching, its ESR also affects efficiency. capacitor is placed right next to the IC.
Rev1.0 Preliminary and all contents are subject to change without prior notice. choose a capacitor with less than 50mΩ ESR. Figure 2. Stability Compensation
- The DC loop gain of the system is determined by the
easy to cause overshoot at power on.
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com .cn • Page 7 9/4/2012 SE1482 2A 27V Synchron ous Buck Converter STEP3. If the output capacitor’s ESR is high enough to cause a zero at lower than 4 times the cros sover frequency, an additional compensation capacitor CCOMP2 is required. The condition for using CCOMP2 is: And the proper value for CCOMP2 is: Though CCOMP2 is unnecessary when the output capacitor has sufficiently low ESR, a small value CCOMP2 such as 100pF may improve stability against PCB layout parasitic effects Table 4－ Component Selection Guide for Stability Compensation Vin Range (V) Vout (V) Cout Rcomp (R3)(kΩ) Ccomp (C4)(nF) Ccomp2 (C5)(pF) Inductor (uH) 5 – 12 1.0 22uFx2 Ceramic 3.3 5.6 none 4.7 5 – 15 1.2 3.9 4.7 none 4.7 5 – 15 1.8 5.6 3.3 none 10 5 – 15 2.5 8.2 2.2 none 10 5 – 15 3.3 10 2 none 10 5 – 15 5 10 3.3 none 10 5 – 12 1.0 470uF/ 6.3V/120mΩ 6.8 680 4.7 5 – 15 1.2 5 – 23 1.8 5 – 27 2.5 5 – 27 3.3 5 – 27 5
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com .cn • Page 8 9/4/2012 SE1482 2A 27V Synchron ous Buck Converter Outline Drawing For SOP8 4 5 H E D A B C MIN MAX MIN MAX A 0.0532 0.0688 1.35 1.75 A1 0.0040 0.0098 0.10 0.25 B 0.0130 0.0200 0.33 0.51 C 0.0075 0.0098 0.19 0.25 D 0.1890 0.1968 4.80 5.00 H 0.2284 0.2440 5.80 6.20 E 0.1497 0.1574 3.80 4.00 DIMENSIONS 0.050 BSC 1.27 BSC DIMN INCHES MM Outline Drawing For PSOP8
Rev1.0 Preliminary and all contents are subject to change without prior notice. © Seaward Electronics, Inc., • www.seawardinc.com .cn • Page 9 9/4/2012 SE1482 2A 27V Synchron ous Buck Converter 联系方式： 北京思旺电子技术有限公司–中国总部 地址：中国北京市海淀区信息路22 号上地科技综合楼B 座二层 邮编：100085 电话:010-82895700/1/5 传真:010-82895706 Seaward Electronics Corporation – 台湾办事处 2F, #181, Sec. 3, Minquan East Rd, Taipei, Taiwan R.O.C 电话: 886-2-2712-0307 传真: 886-2-2712-0191 Seaward Electronics Incorporated – 北美办事处 1512 Centre Pointe Dr. Milpitas, CA95035, USA 电话: 1-408-821-6600