поискавой системы для электроныых деталей |
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3N152 датащи(PDF) 9 Page - RICOH electronics devices division |
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3N152 датащи(HTML) 9 Page - RICOH electronics devices division |
9 / 19 page 12345 Rev. 1.11 - 9 - tonc=T ´VIN/VOUT××× Equation 2 When ton<tonc, the mode is the discontinuous mode, and when ton=tonc, the mode is the continuous mode. n OUTPUT CURRENT AND SELECTION OF EXTERNAL COMPONENTS When LxTr is ON: (Wherein, Ripple Current P-P value is described as IRP, ON resistance of LXTr is described as Rp the direct current of the inductor is described as RL.) VIN=VOUT+(Rp+RL) ´IOUT+L´IRP/ton ×××Equation 3 When LxTr is OFF: L ´IRP/toff = VF+VOUT+RL´IOUT ×××Equation 4 Put Equation 4 to Equation 3 and solve for ON duty, ton/(toff+ton)=DON, DON=(VOUT+VF+RL ´IOUT)/(VIN+VF-Rp´IOUT)×××Equation 5 Ripple Current is as follows; IRP=(VIN-VOUT-Rp ´IOUT-RL´IOUT)´DON/f/L ¼Equation 6 wherein, peak current that flows through L, LxTr, and SD is as follows; ILmax=IOUT+IRP/2 ¼Equation 7 Consider ILmax, condition of input and output and select external components. HThe above explanation is directed to the calculation in an ideal case in continuous mode. n External Components 1. Inductor Select an inductor that peak current does not exceed ILmax. If larger current than allowable current flows, magnetic saturation occurs and make transform efficiency worse. When the load current is same, the smaller value of L, the larger the ripple current. Provided that the allowable current is large in that case and DC current is small, therefore, for large output current, efficiency is better than using an inductor with a large value of L and vice versa. 2. Diode Use a diode with low VF (Schottky type is recommended.) and high switching speed. Reverse voltage rating should be more than VIN and current rating should be equal or more than ILmax. 3. Capacitor As for CIN, use a capacitor with low ESR(Equivalent Series Resistance) and a capacity of at least 10 mF for stable operation. COUT can reduce ripple of Output Voltage, therefore 47 to 100 mF tantalum type is recommended. 4. Lx Transistor Pch Power MOS FET is required for this IC. Its breakdown voltage between gate and source should be a few volt higher than Input Voltage. In the case of Input Voltage is low, to turn on MOS FET completely, select a MOS FET with low threshold voltage. If a large load current is necessary for your application and important, choose a MOS FET with low ON resistance for good efficiency. If a small load current is mainly necessary for your application, choose a MOS FET with low gate capacity for good efficiency. Maximum continuous drain current of MOS FET should be larger than peak current, ILmax. |
Аналогичный номер детали - 3N152 |
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Аналогичное описание - 3N152 |
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