LTM4639

13

4639f

For more information www.linear.com/LTM4639

together to share the current evenly. Figure 24 shows a

schematic of the parallel design.

Input RMS Ripple Current Cancellation

Application Note 77 provides a detailed explanation of

multiphase operation. The input RMS ripple current

cancellation mathematical derivations are presented, and

a graph is displayed representing the RMS ripple current

reductionasafunctionofthenumberofinterleavedphases

(see Figure 2).

PLL, Frequency Adjustment and Synchronization

FREQ

500kHz / V

+0.2V













1

10µA

APPLICATIONS INFORMATION

Figure 3. Relationship Between Switching

Figure 2. Normalized Input RMS Ripple Current vs Duty Cycle for One to Six µModule Regulators (Phases)

0.75 0.8

4639 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

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

0

0.5

1

1.5

2

4639 F03

2.5

0

100

300

400

500

900

800

700

200

600

shown in Figure 3. For low output voltages from 0.6V to

1.2V, 300kHz operation is an optimal frequency for the

best power conversion efficiency while maintaining the

inductor current to about 40% to 50% of maximum load

current. For output voltages from 1.5V to 1.8V, 450kHz

is optimal. For output voltages from 2.5V to 5V, 600kHz