Feb21-07

SP7661 Evaluation Manual

©2007 Sipex Corporation

Page 6 of 11

Figure 9. Voltage Mode Control Loop with Loop Dynamic for Type III Compensation

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

component values for Type III compensation are as follows. As a particular example, consider

for the following SP7661EB with a Type III Voltage Loop Compensation component selections:

Input requirements and inductor selection

Vin = 12V, we will use 12V as Vin max for this design.

Vout = 3.30V @ 0 to 3A load

Select L = 2.2uH => yield

≈ 60% of maximum 3A output current ripple.

Select Cout = 100uF Ceramic capacitor (Resr

≈ 3mΩ) Given the performance of ceramic caps

we will use ~80% of the output capacitance in calcualations.

fs = 600khz SP7661 internal Oscillator Frequency

Vramp_pp = 1.0V SP7661 internal Ramp Peak to Peak Amplitude