19

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SC2620

POWER MANAGEMENT

Applications Information

This is also equal to









+

2

1

2

5

MA

OUT

MP

R

R

R

R

G

R

G

. Therefore

n

10

R

C

R

R

R

R

G

R

G

OUT

1

S

2

1

2

5

MA

OUT

MP

ω

=









+

.

Re-arranging,

MA

MP

1

S

2

1

5

G

nG

10

C

R

R

1

R

ω









+

=

(11)

ω

60

6

S

C

1

z

ω

=

ω

=

ω

gives a first-order estimate of C

5

S

5

R

60

C

ω

≈

(12)

Notice that R

converter. Increasing R

the crossover frequency. However it reduces the phase

margin. C

Bode Plots of Control-to-Ouput, Output-to-Control and the Overall Loop Gain.

Control-to-output transfer function is shown with two poles near half the

switching frequency

ω

Figure 12.

2

p

ω

1

R

n

5

R

1

1

p

ω

3

p

ω

6

R

1

5

R

1

1

Z

ω

C

ω

ω

Gain

2

S

ω

OUT

G









+

2

1

2

O

MA

R

R

R

R

G









+

2

1

2

5

MA

R

R

R

R

G

n

R

C

OUT

1

C

ω

)

j

(

T

ω

OUT

COMP

v

v

Control-to-Output

Transfer Function