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Moteur de recherche de fiches techniques de composants électroniques |
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SI9124 Datasheet(Fiches technique) 11 Page - Vishay Siliconix |
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11 page 
Si9124 Vishay Siliconix New Product Document Number: 72099 S-03638—Rev. B, 20-Mar-03 www.vishay.com 11 Hiccup Operation Current limiting is achieved by monitoring the differential voltage between CS1 and CS2 pins which are connected across a primary sense resistor. Once the differential voltage exceeds the 150-mV trigger point, Hiccup operation is started. The soft-start voltage on the SS pin is pulled to ground and switching stops until the SS pin charges up to 2 Vbe whereupon a duty cycle limited soft start is initiated. The upper and lower switching points of the current limit have 50 mV of hysteresis. VINEXT Voltage Monitor – VINDET The Si9124 provides a means of sensing the voltage on VINEXT to control the operating mode and provides the feed-forward control voltage to the PWM controller. This is achieved by choosing an appropriate resistive tap between VINEXT and ground. When the VINDET voltage is greater than 720 mV but less than VREF and VCC is greater than VUVLO, all internal circuitry is enabled, but switching is stopped. VINDET also provides the input to the voltage feed-forward function by adjusting the amplitude of the PWM ramp to the PWM comparator. Shutdown Mode If VINDET pin is forced below 470 mV the device will enter SHUTDOWN mode. This powers down all unnecessary functions of the controller, ensures that the primary switches are off and results in a low level current demand of 150 mA from the VINEXT or VCC supplies. TYPICAL CHARACTERISTICS 7.5 8.0 8.5 9.0 9.5 10.0 - 50 - 25 0 25 50 75 100 125 150 7.90 7.95 8.00 8.05 8.10 8.15 8.20 - 50 - 25 0 25 50 75 100 125 150 VREG vs. Temperature, VIN = 48 V Temperature ( _C) VINDET u VREF TC = - 11 mV/C VSS vs. Temperature, VCC = 12 V Temperature ( _C) TC = +1.25 mV/C VINDET u VREF 15 17 19 21 23 25 - 50 - 25 0 25 50 75 100 125 ISS1 vs. VCC vs. Temperature Temperature ( _C) VCC = 13 V 80 90 100 110 120 130 140 - 50 - 25 0 25 50 75 100 125 ISS2 vs. VCC vs. Temperature Temperature ( _C) VCC = 10 V VCC = 12 V VCC = 13 V VCC = 10 V VCC = 12 V |
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