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LTM4661 Folha de dados(PDF) 9 Page - Linear Technology |
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LTM4661 Folha de dados(HTML) 9 Page - Linear Technology |
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9 / 20 page  LTM4661 9 4661f For more information www.linear.com/LTM4661 TIME (µs) 0 3.5 3.0 2.0 1.0 2.5 1.5 0.5 0 1.0 4661 F01 1.5 0.5 SINGLE PHASE DUAL PHASE Figure 1. Comparison of Output Ripple Current with Single Phase and Dual Phase Boost Converter Input Decoupling Capacitors The LTM4661 module should be connected to a low AC- impedance DC source. For each module, one piece 10µF input ceramic capacitor is required for RMS ripple current decoupling. Bulk input capacitor is only needed when the inputsourceimpedanceiscompromisedbylonginductive leads, traces or not enough source capacitance. The bulk capacitor can be an electrolytic aluminum capacitor and polymer capacitor. Output Decoupling Capacitors With an optimized high frequency, high bandwidth, two phase interleaving design, only single piece of 22µF low ESRoutputceramiccapacitorisrequiredforeachLTM4661 module to achieve low output voltage ripple and very good transient response. Additional output filtering may be required by the system designer, if further reduction of output ripples or dynamic transient spikes is required. The LTpowerCAD® Design Tool is available to download online for output ripple, stability and transient response analysis. Soft-Start The LTM4661 contains internal circuitry to provide soft- start operation. The soft-start utilizes a linearly increasing ramp of the error amplifier reference voltage from zero to its nominal value of 1.2V in approximately 10ms, with the internal control loop driving VOUT from zero to its final programmed value. This limits the inrush current drawn APPLICATIONS INFORMATION from the input source. As a result, the duration of the soft-start is largely unaffected by the size of the output capacitor or the output regulation voltage. The soft-start period is reset by a shutdown command on SDB, a UVLO event on INTVCC (INTVCC < 1.5V), an overvoltage event on VOUT (VOUT ≥ 16.5V), or an overtemperature event (TSD is invoked when the die temperature exceeds 170°C). Upon removal of these fault conditions, the LTM4661 will soft- start the output voltage. Burst Mode Operation In applications where high efficiency at light load current are more important than output voltage ripple, Burst Mode operation could be used by connecting SYNC/MODE pin to GND to improve light load efficiency. The output current (IOUT) capability in Burst Mode operation is significantly less than in continuous current mode (CCM) and varies with VIN and VOUT, as shown in Figure 2. The LTM4661 will operate in CCM mode even if Burst Mode operation is commanded during soft-start. In Burst Mode operation, only one phase of the LTM4661 isoperational,whiletheotherphaseisdisabled.Thephase inductor current is initially charged to approximately 700mA by turning on the N-channel MOSFET switch, at which point the N-channel switch is turned off and the P-channel synchronous switch is turned on, deliv- ering current to the output. When the inductor current discharges to approximately zero, the cycle repeats. In VIN, FALLING (V) 1 300 400 5 4661 F02 200 100 250 350 150 50 0 2 3 4 1.5 0.5 2.5 3.5 4.5 5.5 VOUT = 2.5V VOUT = 5V VOUT = 7.5V VOUT = 12V VOUT = 15V Figure 2. Burst Mode Output Current vs VIN |
Nº de peça semelhante - LTM4661 |
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Descrição semelhante - LTM4661 |
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