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LTC1434C 数据表(PDF) 6 Page - Linear Technology |
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LTC1434C 数据表(HTML) 6 Page - Linear Technology |
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6 / 20 page  6 LTC1433/LTC1434 FUNCTIONAL DIAGRA OPERATION (Refer to Functional Diagram) Main Control Loop The LTC1433/LTC1434 is a constant frequency, pulse- width modulated current mode switching regulator. Dur- ing normal operation, the internal P-channel power MOSFET is turned on each cycle when the oscillator sets the RS latch FF3, and turned off when the main current compara- tor ICOMP resets the latch. The peak inductor current at which the ICOMP resets the RS latch is controlled by the voltage on the ITHpin , which is the output of error amplifier GM. Pins VPROG and VOSENSE, described in the Pin Func- tions section, allow GM to receive an output feedback voltage VFB from either the internal or external resistive dividers. When the load current increases, it causes a slight decrease in VFB relative to the 1.19V reference, which in turn causes the ITH voltage to increase until the average inductor current matches the new load current. The main control loop is shut down by pulling the RUN/SS pin low. Releasing RUN/SS allows an internal 3 µA current source to charge up the soft start capacitor CSS. When CSS reaches 1.3V, the main control loop is enabled with the ITH voltage clamped at approximately 30% of its maximum value. As CSS continues to charge, ITH is gradually re- leased allowing normal operation to resume. Comparator OVDET guards against transient overshoots > 7.5% by turning off the P-channel power MOSFETs and keeping them off until the fault is removed. Low Current Operation The LTC1433/LTC1434 have two internal P-channel MOSFETs sized for low and high load current conditions. At low load current, only the small MOSFET will be turned on while at high load current both MOSFETs will be on. – + – + – + – + LOBAT – + GM LIDET OVDET POR BSW PWRVIN SSW ITH LBI LBO VREF PLL LPF PLLIN COSC 180k 0.6V SVIN 30k 6V VREF + 89mV VSET IPEAK DET ICOMP 12mV RUN/SS 50k 120k REF AND VCC SHDN VREF (1.19V) VREF PGND SGND VCC SVIN RB SB Q Q FF3 RB SB Q Q FF2 D CK Q Q FF1 POR PLL SHDN SHDN FREQ SHIFT OSC VCO SLOPE COMP RSENSE 0.143 Ω VOLTAGE SELECT 60k 240k 60k VPROG VOSENSE 1433/34 FD |
类似零件编号 - LTC1434C |
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类似说明 - LTC1434C |
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