поискавой системы для электроныых деталей |
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UC3550-XX-AF5-R датащи(PDF) 7 Page - Unisonic Technologies |
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UC3550-XX-AF5-R датащи(HTML) 7 Page - Unisonic Technologies |
7 / 10 page UC3550 CMOS IC UNISONICTECHNOLOGIESCO.,LTD 7 of 10 www.unisonic.com.tw QW-R502-082,A EXTERNAL COMPONENT SELECTION Inductor Selection An inductor value of 10uH performs well in most application. The UC3550 series also work with inductors in the 4.7uH to 12uH range. An inductor with higher peak inductor current tends a higher output voltage ripple(IPEAK x output filter capacitor ESR). The inductor’s DC resistance significantly affects efficiency. Output Capacitor Selection The output ripple voltage(IPEAK x output filter capacitor ESR)is the product of the peak inductor current and the output capacitor Equivalent Series Resistance (ESR). Best performances are obtained with good high frequency characteristics capacitors and low ESR. The best compromise for the value of the Output Capacitance is 220F Tantalum Capacitor. The output capacitor as close as possible to the device pins. Input Capacitor Selection The Input Capacitor is required to compensate, if present, the series impedance between the Supply Voltage Source and the Input Voltage of the Application. A value of 10 F is enough to guarantee stability for distances less than 2". In any case we suggest to connect both capacitors, The input capacitor as close as possible to the device pins. Diode Selection The Schottky diode with an high switching speed and a very low Forward Voltage (VF) is needed. Higher VF may cause lost power as heat in the diode, with a decrease of the Efficiency. Moreover, since the Output Voltage pin is also used as the device Supply Voltage, the Start-up Voltage (see related plots) is strictly due to the diode Forward Voltage at the rated Forward Current. External Component Selection An enhancement N-channel MOSFET or a bipolar NPN transistor can be used as the external switch transistor. since enhancement N-channel MOSFET is a voltage driven device, it is a more efficient switch than a BJT transistor. However, he MOSFET requires a higher voltage to turn on as compared with BJT transistor For enhancement N-channel MOSFET ( it is especially importance for RDS(ON),typically<0.1Ω, threshold voltage, VGS(TH) must be<VOUT, typically<1.5V. For bipolar NPN transistor, continuous collector current typically 1A to 4A and VCE(SAT)<0.2V. the driving capability is determined by the DC current gain, HFE, of the transistor and the base resistor, Rb. Moreover, a speed-up capacitor, Cb should be connected in paralled with Rb to reduce switch loss and improve efficiency. |
Аналогичный номер детали - UC3550-XX-AF5-R |
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Аналогичное описание - UC3550-XX-AF5-R |
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