LTM4643 datasheet(13/30 Pages) AD

13 / 30 page

LTM4638

Rev. C

For more information www.analog.com

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 when all of the outputs are tied together

to achieve a single high output current design.

The LTM4638 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 COMPa

pins of each paralleling channel together. Figure 25 shows

an example of parallel operation and pin connection.

APPLICATIONS INFORMATION

Figure 3. 4-Phase, 6-Phase Operation

Figure 4. RMS Input Ripple Current to DC Load Current Ratio as a Function of Duty Cycle

4638 F03

CLKIN

PHMODE

CLKOUT

180

270

+90

PHASE 4

PHASE 3

PHASE 2

PHASE 1

CLKIN

PHMODE

CLKOUT

CLKIN

PHMODE

CLKOUT

CLKIN

PHMODE

CLKOUT

CLKIN

PHMODE

CLKOUT

120

240

(420)

180

+120

+180

+120

PHASE 4

INTVCC

PHASE 2

PHASE 5

PHASE 3

CLKIN

PHMODE

CLKOUT

CLKIN

PHMODE

CLKOUT

CLKIN

PHMODE

CLKOUT

300

+120

PHASE 6

CLKIN

PHMODE

CLKOUT

PHASE 1

CLKIN

PHMODE

CLKOUT

+120

0.75 0.8

4638 F04

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)

0.05

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

LTM4643 Datasheet(PDF) 13 Page - Analog Devices

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