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Moteur de recherche de fiches techniques de composants électroniques |
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Moteur de recherche de fiches techniques de composants électroniques |
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LM2682MMX Fiches technique(PDF) 4 Page - National Semiconductor (TI) |
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LM2682MMX Fiches technique(HTML) 4 Page - National Semiconductor (TI) |
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4 / 7 page  Basic Application Circuits Application Information Voltage Doubling Inverter The main application of the LM2682 is to generate a nega- tive voltage that is twice the positive input voltage. This cir- cuit requires only three external capacitors and is connected as shown in Figure 1. It is important to keep in mind that the efficiency of the circuit is determined by the output resis- tance. A derivation of the output resistance is shown below: R OUT = 2(R SW1+RSW2+ESRC1+RSW3+RSW4+ESRC2)+ 2(R SW1+RSW2+ESRC1+RSW3+RSW4+ESRC2)+ 1/(f OSCxC1) + 1/(fOSCxC2) + ESRC3 Using the assumption that all four switches have the same ON resistance our equation becomes: R OUT = 16R SW + 4ESRC1 + 4ESRC2 + ESRC3 + 1/(f OSCxC1) + 1/(fOSCxC2) Output resistance is typically 90 Ω with an input voltage of +5V, an operating temperature of 25˚C, and using low ESR 3.3 µF capacitors. This equation shows the importance of capacitor selection. Large value, low ESR capacitors will re- duce the output resistance significantly but will also require a larger overall circuit. Smaller capacitors will take up less space but can lower efficiency greatly if the ESR is large. Also to be considered is that C1 must be rated at 6 VDC or greater while C2 and C3 must be rated at 12 VDC or greater. The amount of output voltage ripple is determined by the out- put capacitor C3 and the output current as shown in this equation: V RIPPLE P-P = IOUT x (2xESRC3 + 1/[2x(fOSCxC3)]) Once again a larger capacitor with smaller ESR will give bet- ter results. DS100997-3 FIGURE 1. Doubling Voltage Inverter DS100997-4 FIGURE 2. +5V to −5V Regulated Voltage Converter www.national.com 4 |
Numéro de pièce similaire - LM2682MMX |
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Description similaire - LM2682MMX |
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