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ACE708 Folha de dados(PDF) 3 Page - ACE Technology Co., LTD. |
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ACE708 Folha de dados(HTML) 3 Page - ACE Technology Co., LTD. |
3 / 8 page ACE708 300mA Iout, 0.85V startup, 1.2MHz, Synchronous Boost Converter VER 1.4 3 Detail Description ACE708 is a low input voltage start up, current mode dc- dc step up converter. It’s operation can be best understood by referring to the block diagram. Upon starting up, the low voltage startup circuitry drives SW with on-off cycles, transferring energy from input to OUT by storing energy in the inductor during on-time and releasing it to the output during off-time. When OUT reaches 2V, the startup circuit turns off and the main controller takes over. The main control loop consists of a reference, a GM error amplifier, a PWM controller, a current sense amplifier, an oscillator, a PWM logic control, and it is power stage including its driver. The main control loop is a classic current mode control loop. The GM stage integrates the error between FB and REF, and its output is used to compare with a triangular wave which the summing result of the current sense amplifier output and a slope compensation voltage. The output of the comparator is used to drive the power stage to reach regulation. Application Information Output Voltage selection The output voltages can be set by connecting FB to OUT, to G or to the midpoint of a resistor divider connected to OUT. See below table for details. Inductor selection With switching frequency up to 1MHz, small surface mount inductors can be used with values from 2.2uH to 4.7uH. For a given chosen inductor value and application conditions make sure the peak inductor current does not exceed the maximum current rating of the selected vendor's inductor. Input and output capacitor selection The ACE708's bootstrap architecture allows the use of very small input capacitor. For applications that only need to drive small output load current, the input capacitor is optional, because once output is started up, the IC's is powered by OUT, a quiet power supply. The output capacitor is used to stabilize the loop and provide ac current to the load. A low ESR ceramic cap with values from 2.2uF to 22uF can be used. Smaller value capacitors are generally cheaper with small footprints, while larger capacitor provides lower ripples and better transient load responses. Also, when extreme low startup voltage is needed, larger output capacitors are needed for the part to startup under heavy load condition. FB=G VOUT=5.0V FB=OUT VOUT=3.3V FB to resistor divider VOUT=0.6V(1+R1/R2) |
Nº de peça semelhante - ACE708_12 |
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Descrição semelhante - ACE708_12 |
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