Rev 5/01/06

SP6136 Evaluation Manual

Copyright © 2006 Sipex Corporation

Page 6 of 9

The simple guidelines for positioning the poles and zeros and for calculating the component

values for Type III compensation are as follows:

K

R

1

.

68

1

=

8

.

0

1

8

.

0

2

−

×

=

Vout

R

R

(sets output voltage)

LC

R

ZSF

CZ

1

1

1

3

×

×

=

(sets first zero)

(

)

(

)

Vin

Vramp

CZ

fc

Cout

L

fc

RZ

×

×

×

+

×

×

×

=

3

28

.

6

1

28

.

6

2

2

(sets the cross-over frequency, fc)

LC

RZ

ZSF

CZ

1

2

1

2

×

×

=

(sets second zero)

2

28

.

6

1

1

RZ

fs

CP

×

×

=

(sets first high-frequency pole)

3

28

.

6

1

3

CZ

fs

RZ

×

×

=

(sets second high-frequency pole)

Where ZSF=(f compensation double zero)/(f circuit double pole)

Here ZSF is set at 0.8.

As a particular example, consider for the following SP6136EB, 7AMAX with a type III Voltage

Loop Compensation component selections:

Vin = 12V

Vout = 3.30V @ 0 to 7A load

Select L = 2.2 uH => 30% current ripple.

Select Cout = 100uF Ceramic capacitor (Resr ≈ 5mΩ)

fs = 600KHz SP6136ER1 internal Oscillator Frequency

Vramp_pp = 1.0V SP6136ER1 internal Ramp Peak to Peak Amplitude