LTM4643 datasheet(12/32 Pages) LINER

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LTM4643

4643fb

For more information www.linear.com/LTM4643

APPLICATIONS INFORMATION

Figure 2. Normalized RMS Ripple Current for Single Phase or Polyphase Applications

The LTM4643 device is an inherently current mode con-

trolled device, so parallel modules will have very good

current sharing. This will balance the thermals on the

design. Please tie the RUN, TRACK/SS, FB and COMP

pins of each paralleling channel together. Figure 31 and

Figure 32 show an example of parallel operation and pin

connection.

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.

Figure 2 shows this graph.

Soft-Start and Output Voltage Tracking

The TRACK/SS pin provides a means to either soft-start

of each regulator channel or track it to a different power

supply. A capacitor on the TRACK/SS pin will program the

ramp rate of the output voltage. An internal 2.5µA current

source will charge up the external soft-start capacitor

DUTY CYCLE (VOUT/VIN)

0.1 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

0.60

0.55

0.50

0.45

0.40

0.35

0.30

0.25

0.20

0.15

0.10

0.05

4643 F02

1-PHASE

2-PHASE

4-PHASE

Figure 1. 2+2 and 4 Channels Parallel Concept Schematic

4643 F01

VOUT1

CH1

(0°)

VOUT2

LTM4643

CH2

(180°)

180°

VOUT3

CH3

(0°)

VOUT4

CH4

(180°)

180°

VOUT1

CH1

(0°)

VOUT2

LTM4643

12A

CH2

(180°)

180°

VOUT3

CH3

(270°)

VOUT4

CH4

(90°)

180°

90°

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