LTM4657

12

Rev. A

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A multiphase power supply significantly reduces the

amount of ripple current in both the input and output

capacitors. 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 LTM4657 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 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

4657 F03

CLKIN

PHMODE

CLKOUT

0

90

180

270

+90

+90

+90

PHASE 4

PHASE 3

PHASE 2

PHASE 1

CLKIN

PHMODE

CLKOUT

CLKIN

PHMODE

CLKOUT

CLKIN

PHMODE

CLKOUT

CLKIN

PHMODE

CLKOUT

120

240

(420)

60

180

+120

+180

+120

PHASE 4

PHASE 2

PHASE 5

PHASE 3

CLKIN

PHMODE

CLKOUT

CLKIN

PHMODE

CLKOUT

CLKIN

PHMODE

CLKOUT

300

+120

PHASE 6

CLKIN

PHMODE

CLKOUT

0

PHASE 1

CLKIN

PHMODE

CLKOUT

+120

0.75 0.8

4657 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

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