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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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L6599AF Fiches technique(PDF) 5 Page - STMicroelectronics |
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L6599AF Fiches technique(HTML) 5 Page - STMicroelectronics |
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5 / 32 page  DocID028175 Rev 3 5/32 L6599AF Pin connection 32 3 Pin connection Figure 2. Pin connection (top view) Table 2. Pin description Pin no. Type Function 1Css Soft-start. This pin connects an external capacitor to GND and a resistor to RFmin (pin 4) that set both the maximum oscillator frequency and the time constant for the frequency shift that occurs as the chip starts up (soft-start). An internal switch discharges this capacitor every time the chip turns off (Vcc < UVLO, LINE < 1.24 V or > 6 V, DIS > 1.85 V, ISEN > 1.5 V, DELAY > 2 V) to make sure it is soft-started next, and when the voltage on the current sense pin (ISEN) exceeds 0.8 V, as long as it stays above 0.75 V. 2DELAY Delayed shutdown upon overcurrent. A capacitor and a resistor are connected from this pin to GND to set the maximum duration of an overcurrent condition before the IC stops switching and the delay after which the IC restarts switching. Every time the voltage on the ISEN pin exceeds 0.8 V, the capacitor is charged by an internal 150 µA current generator and is slowly discharged by the external resistor. If the voltage on the pin reaches 2 V, the soft-start capacitor is completely discharged so that the switching frequency is pushed to its maximum value and the 150 µA is kept always on. As the voltage on the pin exceeds 3.5 V the IC stops switching and the internal generator is turned off, so that the voltage on the pin decays because of the external resistor. The IC is soft-restarted as the voltage drops below 0.3 V. In this way, under short-circuit conditions, the converter works intermittently with very low input average power. 3CF Timing capacitor. A capacitor connected from this pin to GND is charged and discharged by internal current generators programmed by the external network connected to pin 4 (RFmin) and determines the switching frequency of the converter. 4RFmin Minimum oscillator frequency setting. This pin provides a precise 2 V reference and a resistor connected from this pin to GND defines a current that is used to set the minimum oscillator frequency. To close the feedback loop that regulates the converter output voltage by modulating the oscillator frequency, the phototransistor of an optocoupler is connected to this pin through a resistor. The value of this resistor sets the maximum operating frequency. An R-C series connected from this pin to GND sets frequency shift at startup to prevent excessive energy inrush (soft-start). |
Numéro de pièce similaire - L6599AF |
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Description similaire - L6599AF |
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