Datasheet LTM4671 (Analog Devices) - 18

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APPLICATIONS INFORMATION
0.60 1-PHASE 2-PHASE 0.55 3-PHASE 4-PHASE 0.50 6-PHASE 0.45 0.40 0.35 0.30 0.25 DC LOAD CURRENT RMS INPUT RIPPLE CURRENT 0.20 0.15 0.10 0.05 00.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 DUTY FACTOR (VOUT/VIN) 4671 F03
Figure 3. Input RMS Current Ratios to DC Load Current as a Function of Duty Cycle SOFT-START AND OUTPUT VOLTAGE TRACKING
Figure 4 and Figure 5 show an example waveform and The TRACK/SS pin provides a means to either soft-start schematic of a ratiometric tracking where the slave of each regulator channel or track it to a different power regulator’s (VOUT2, VOUT3 and VOUT0) output slew rate is supply. A capacitor on the TRACK/SS pin will program the proportional to the master’s (VOUT1). ramp rate of the output voltage. An internal soft-start cur- rent source will charge up the external soft-start capacitor towards INTV VOUT1 = 3.3V CC voltage. When the TRACK/SS voltage is below 0.6V, it will take over the internal 0.6V reference VOUT2 = 2.5V voltage to control the output voltage. The total soft-start TAGE VOUT3 = 1.2V time can be calculated as: V C OUT0 = 1.0V t SS SS = 0.6 • I OUTPUT VOL SS where CSS is the capacitance on the TRACK/SS pin and the ISS is the soft-start current which equals 6µA for the 12A output channels (CH0, CH3) and 1.4µA for the 5A TIME 4671 F04
Figure 4. Output Ratiometric Tracking Waveform
output channels (CH1, CH2). Output voltage tracking can also be programmed externally using the TRACK/SS pin of each regulator channel. The output can be tracked up and down with another regulator. Rev. B 18 For more information www.analog.com Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Decoupling Requirements Operation Applications Information Typical Applications Component BGA Pinout Package Description Revision History Package Photo Related Parts