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MAP3242 データシート(PDF) 17 Page - MagnaChip Semiconductor. |
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MAP3242 データシート(HTML) 17 Page - MagnaChip Semiconductor. |
17 / 22 page Confidential Datasheet Version 1.1 Jun 13 th 2013 17 Output Rectifying Diode Schottky diodes are the ideal choice for MAP3242 due to their low forward voltage drop and fast switching speed. Make sure that the diode has a voltage rating greater that the possible maximum output voltage. The diode conducts current only when the power switch is turned off. Input Capacitor In boost converter, input current flows continuously into the inductor; AC ripple component is only proportional to the rate of the inductor charging, thus, smaller value input capacitors may be used. Ensure the voltage rating of the input capacitor is suitable to handle the full supply range. A capacitor with low ESR should be chosen to minimize heating effects and improve system efficiency. Output Capacitor The output capacitor acts to smooth the output voltage and supplies load current directly during the conduction phase of the power switch. Output ripple voltage consists of the discharge of the output capacitor during the FET ton period and the voltage drop due to load current flowing through the ESR of the output capacitor. The ripple voltage is shown in following equation. ESR I f C D I V OUT SW OUT OUT OUT × + × × = ∆ Assume a ceramic capacitor is used. The minimum capacitance needed for a given ripple can be estimated by following equation. OUT SW OUT OUT OUT IN OUT V f V I V V C ∆ × × × − = ) ( Loop Compensation The MAP3242 controls in current mode. Current mode easily achieves compensation by consisting simple single pole from double pole that LC filer makes at voltage mode. In general, crossover frequency is selected from 1/3 ~ 1/6 range of the switching frequency. If fc is large, there is possibility of oscillation to occur, although time response gets better. On the other hand, if fc is small, time response will be bad, while it has improved stability, which may cause over shoot or under shoot in abnormal condition. Layout Consideration A gate drive signal output from GATE pin becomes noise source, which may cause malfunction of IC due to cross talk if placed by the side of an analog line. It is recommended to avoid placing the output line especially by the side of CS, ADIM, ISET, FSW, OVP, COMP, VLS pins as far as possible. All the GND of MAP3242, AGND, PGND and LGND(HSOP), are totally seperated internally. For GND layout, it is the best that all the GNDs are seperated to improve noise immunity and avoid unstability. If layout difficulty is high, the second best is tying PGND and LGND(HSOP) and seperating AGND. Followings are GND layout rules for each package. (1) HSOP - Tie PGND/LGND and seperate AGND - Heak sink pins(HS1, HS2) shoud be tied to AGND (2) SOIC - Separate AGND and PGND (3) ETSSOP - Separate AGND and PGND - Exposed pad shoud be tied to AGND with multiple vias |
同様の部品番号 - MAP3242 |
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同様の説明 - MAP3242 |
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