Mar12-07 RevD

SP7663 Evaluation Board Manual

©2007 Sipex Corp.

Page 8 of 16

Calculate CZ2 by placing the zero at ½ of the output filter pole frequency

LC

fp

RZ

CZ

_

2

1

2

⋅

⋅

=

π

nF

nF

KHz

K

CZ

1

055

.

1

13

2

.

23

1

2

≈

=

⋅

Ω

⋅

=

π

Calculate CP1 by placing the first pole at ESR zero frequency

)

_

2

(

2

1

1

ESR

fz

Rz

CP

⋅

⋅

=

π

pF

pF

KHz

K

CP

10

84

.

5

)

400

1

.

68

(

2

1

1

≈

=

⋅

⋅

=

π

Calculate RZ3 by setting the second pole at ½ of the switching frequency and the

second zero at the output filter double pole frequency

LC

fp

fs

LC

fp

R

RZ

_

2

)

_

(

)

1

(

2

3

−

⋅

⋅

=

Ω

=

−

⋅

Ω

⋅

=

K

KHz

f

KHz

KHz

K

RZ

084

.

3

13

2

600

)

13

(

)

1

.

68

(

2

3

Calculate CZ3 from RZ3 component value above

fs

RZ

CZ

⋅

⋅

=

3

1

3

π

pF

pF

KHz

K

CZ

180

172

600

084

.

3

1

3

≈

=

⋅

Ω

⋅

=

π

Choose 100pF ≤ CF1 ≤ 220pF to stabilize the SP7663ER internal Error Amplifier