The gained power as a percentage of the output power using the multiphase PWMs instead of synchro-

nized PWMs is :

∆P%(δ) =

Psaved

Po

⋅ 100

∆P%(δ) =

ESR

2

⋅

Iout

Vcc

⋅ 100

So the percentage gained power,

∆P%, for a fixed Iout, Vcc and ESR does not change with the output

voltage.

For example if the input capacitor has an ESR of 100mOhm for a 12V/3.3V or 12V/5V power conversion,

with Iout = 7A, there is in both cases a

∆P% gain of 3% .

Table1 shows in details the major tips for different output voltages.

Table 1. Vcc = 12V , Iout = 7A, ESR=100m

Ω.

Vo

(V)

Irmssync

(A)

Irmsmulti

(A)

∆Irms

(A)

Psync

(W)

Pmulti

(W)

Psaved

(W)

∆P%

Gained

3.3

3.13

1.74

1.39

0.98

0.3

0.68

3%

5.1

3.46

1.25

2.21

1.2

0.16

1.04

3%

6

3.5

0

3.5

1.23

0

1.23

3%

The gained power

∆P% versus duty cycle is shown in figure 10.

0

1

2

3

4

5

6

7

8

9

10

0

0.5

1

1.5

2

Psave(

)

,

,

,

Iout 5.1 12 0.05

Psave(

)

,

,

,

Iout 5.1 12 0.085

Psave(

)

,

,

,

Iout 5.1 12 0.1

Iout

Vo=5.1V

fsw=200kHz

Vcc=12V

50m

Ω

85m

Ω

ESR=100m

Ω

Psaved

[ W ]

[ A ]

Figure 10. Power saved vs. Iout.

AN1126 APPLICATION NOTE

7/16