RT9245 查看數據表（PDF） - Richtek Technology

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RT9245

Multi-Phase PWM Controller for CPU Core Power Supply

Richtek Technology 

RT9245

Current Balance Function

30

IL3

25

IL4

20

IL1

IL2

15

10

5

0

0

20

40

60

80

100

IOUT (A)

Figure 12

L

DCR

ESR

+

-

VCSP

VCSN

C

GMx

RCSN1

Ix

RCSN2

Figure13. Application circuit of GM

For load line design, with application circuit in Figure 13,

it can eliminate the dead zone of load line at light loads.

VCSP = VOUT +IL x DCR

if GM holds input voltages equal, then

VCSP = VCSN

IX

=

VCSN

RCSN2

+ IL × DCR

RCSN1

= VOUT + IL × DCR + IL × DCR

RCSN2

RCSN1

= VOUT + IL × DCR + IL × DCR

RCSN2

RCSN2

RCSN1

For the lack of sinking capability of GM, RCSN2 should be

small enough to compensate the negative inductor valley

current especially at light loads.

VCSN ≥ IL × DCR

RCSN2

RCSN1

www.richtek.com

14

Assume the negative inductor valley current is −5A at no

load, then for

RCSN1 = 330Ω, RADJ = 160Ω, VOUT = 1.300

1.3V −5A × 1mΩ

≥

RCSN2

330Ω

RCSN2 ≤ 85.8kΩ

Choose RCSN2 = 82kΩ

Load Line without dead zone at light loads

1.31

1.3

1.29

1.28

1.27

1.26

RCSN2 open

1.25

RCSN2 = 82k

1.24

1.23

0

5

10

15

20

25

IOUT (A)

Figure 14

VID on the Fly

With external pull up resistors tied to VID pins, RT9245

converters different VID codes from CPU into output

voltage. Figure 12 and Figure 13 show the waveforms of

VID on the fly function.

VID on the Fly (Falling)

PWM

VCORE

VFB

CH1:(5V/Div)

CH2:(500mV/Div)

CH3:(500mV/Div)

CH4:(1V/Div)

VID125

VDAC = 1.500, IOUT = 5A

Time (25μs/Div)

Figure 15

DS9245-06 March 2007

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