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UC3578DPG4 датащи(PDF) 3 Page - Texas Instruments |
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UC3578DPG4 датащи(HTML) 3 Page - Texas Instruments |
3 / 11 page 3 UC2578 UC3578 ELECTRICAL CHARACTERISTICS: Unless otherwise specified VCC = 14V, VGG = 14V, TA =TJ. PARAMETER TEST CONDITIONS MIN TYP MAX UNITS VGG Regulator Section VGG – SRC VCC = 72V, SRC = 0V, IVGG = –7mA 14.5 15.25 17 V VCC = 50V, SRC = 0V, IVGG = –7mA 14 14.75 16 V VCC = 15V, SRC = 0V, IVGG = –7mA 13 13.75 14.5 V VCC = 11V, SRC = 0V, IVGG = –7mA 9.5 10 10.5 V Soft Start Ramp Section Soft Start Ramp Current –30 –45 µA Supply Current Section IVCC EAINV ≥ 2.1V, SRC = 0V 10 14 mA IVGG EAINV ≥ 2.1V, SRC = 0V 7 10.5 mA CS: Peak current limit sense pin. Senses the current across a current sense resistor placed between VCC and the drain of the NMOS buck switch. OUT will be held low (NMOS buck switch off) if VCC – CS exceeds 0.5V. DIODE: An external small signal diode (1N4148 typical) is connected here, anode to VCC and cathode to DIODE, to implement the VGG regulator function. EAINV: Inverting input to error amplifier. VOUT sense feedback is connected to this pin. The non-inverting input of the error amplifier is internally connected to 2V. EAOUT: Output of the error amplifier. Use EAOUT and EAINV for loop compensation components. GND: Circuit Ground. The four ground pins are internally connected together by the fused leadframe of the package. They provide the primary thermal conduction path for dissipating junction heat. OUT: Gate drive for the external NMOS switch connected between VCC and the buck inductor. SRC: This pin is connected to the junction of the external NMOS switch source, the floating voltage source capacitor, the free-wheeling diode cathode, and buck inductor. SS: The external soft start capacitor is connected to this pin. VGG: An external capacitor connected from VGG to SRC completes the floating voltage source for the floating gate driver. A 1 µF capacitor is recommended. VCC: Input supply voltage. This pin supplies an internal ground referenced voltage regulator that supplies the IC and an on-chip regulated floating voltage source (VGG – SRC) used by the floating driver to drive the external NMOS buck switch. This pin should be bypassed with a high quality ceramic capacitor. PIN DESCRIPTIONS The UC3578 Floating Buck Controller is a high frequency switching regulator with a floating driver which provides PWM control for non-isolated buck converters. The con- troller operates at a fixed 100 kHz switching frequency, and in voltage mode control. The duty cycle range of the PWM output is 0% to 90% allowing for a wide range of input voltages (14V minimum with transients to 72V). The regulator features an undervoltage lockout threshold of 11V with approximately 2V hysterisis as well as soft start capability. The typical application circuit shown is for a 15V to 40V input and a 12V at 3A output. To ensure proper operation of the floating driver, an ex- ternal capacitor (1 µF ceramic) must be connected from VGG to SRC, and to the source of the external MOSFET through a small resistor, as shown in the typical applica- tion diagram and in Fig 2. This capacitor provides the en- ergy for the high side driver. The gate drive voltage to the MOSFET is internally regulated to 14V. A diode (1N4148) is required from the input voltage to DIODE. This allows the floating drive capacitor to charge during conduction of the output rectifier but prevents its dis- charge back into the supply rail. A 1 µF ceramic capacitor is recommended from VCC to ground to provide high fre- quency decoupling. Additional decoupling of this pin could be accomplished by a low value resistor between VCC and VIN anda1µF capacitor from VCC to GND as shown in the schematic. APPLICATION INFORMATION Not Recommended for New Designs |
Аналогичный номер детали - UC3578DPG4 |
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Аналогичное описание - UC3578DPG4 |
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