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Datenblatt-Suchmaschine für elektronische Bauteile |
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Datenblatt-Suchmaschine für elektronische Bauteile |
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LTM4636 Datenblatt(PDF) 13 Page - Linear Technology |
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LTM4636 Datenblatt(HTML) 13 Page - Linear Technology |
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13 / 36 page  LTM4636 13 4636f For more information www.linear.com/LTM4636 Multiphase Operation For outputs that demand more than 40A of load current, multipleLTM4636devicescanbeparalleledtoprovidemore output current without increasing input and output ripple voltage. The MODE_PLLIN pin allows the LTM4636 to be synchronized to an external clock and the internal phase- locked loop allows the LTM4636 to lock onto input clock phase as well. The FREQ resistor is selected for normal frequency, then the incoming clock can synchronize the device over the specified range. A multiphase power supply significantly reduces the amount of ripple current in both the input and output ca- pacitors. The RMS input ripple current is reduced by, and the effective ripple frequency is multiplied by, the number of phases used (assuming that the input voltage is greater than the number of phases used times the output voltage). The output ripple amplitude is also reduced by the number of phases used. See Application Note 77. The LTM4636 device is an inherently current mode con- trolled device, so parallel modules will have good current sharing.Thiswillbalancethethermalsinthedesign.Tiethe COMPA to COMPB and then tie the COMPA pins together, tie VFB pins of each LTM4636 together to share the cur- rent evenly. Figure 21 shows a schematic of the parallel design. For external compensation and parallel operation onlytieCOMPApinstogetherwithexternalcompensation. Input RMS Ripple Current Cancellation Application Note 77 provides a detailed explanation of multiphase operation. The input RMS ripple current can- cellation mathematical derivations are presented, and a graph is displayed representing the RMS ripple current reductionasafunctionofthenumberofinterleavedphases (see Figure 2). PLL, Frequency Adjustment and Synchronization TheLTM4636switchingfrequencyissetbyaresistor(RFREQ) from the FREQ pin to signal ground. A 20µA current (IFREQ)flowingoutoftheFREQpinthroughRFREQdevelops a voltage on the FREQ pin. RFREQ can be calculated as: RFREQ = FREQV 20µA applicaTions inForMaTion Figure 2. Normalized Input RMS Ripple Current vs Duty Cycle for One to Six µModule Regulators (Phases) 0.75 0.8 4636 F02 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.85 0.9 DUTY CYCLE (VOUT/VIN) 0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 1 PHASE 2 PHASE 3 PHASE 4 PHASE 6 PHASE |
Ähnliche Teilenummer - LTM4636 |
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Ähnliche Beschreibung - LTM4636 |
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