Mar12-07 RevD

SP7663 Evaluation Board Manual

©2007 Sipex Corp.

Page 11 of 16

1

8

.

1

2

−









=

V

Vout

R

R

Ω

≈

Ω

=

−









Ω

=

K

K

V

V

K

R

5

.

21

79

.

21

1

8

.

3

.

3

1

.

68

2

Select the ratio of RZ2 / R1 gain for the desired gain bandwidth

(

)

fco

LC

Fp

ESR

Fz

Vin

pp

Vramp

R

RZ

⋅

















⋅













⋅

=

2

_

_

max

_

_

1

2

Ω

≈

Ω

=

⋅













⋅













⋅

Ω

=

K

K

Khz

Khz

Khz

V

K

RZ

75

89

.

75

60

2

.

7

13

5

.

13

1

1

.

68

2

2

Calculate CZ2 by placing the zero at 1/10 of the output filter pole frequency

LC

fp

RZ

CZ

_

2

2

1

.

1

2

⋅

⋅

⋅

⋅

=

π

pF

pF

Khz

K

CZ

330

294

2

.

7

75

2

1

.

1

2

≈

=

⋅

Ω

⋅

⋅

⋅

=

π

Calculate CP1 by placing the second pole at ½ of the switching frequency

fs

RZ

CP

⋅

⋅

=

2

1

1

π

pF

pF

Khz

K

CP

10

07

.

7

600

75

1

1

≈

=

⋅

Ω

⋅

=

π

Cf1 = 100pF to stabilize SP7663ER internal Error Amplifier