IP1203PBF datasheet(16/23 Pages) IRF

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iP1203PbF

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More than one iteration may be required to calculate

the values of the compensation components if cross-

over frequencies higher than the range specified in

step 1 are required (for higher bandwidths and faster

transient response performance). To ensure stability

a phase margin greater than 45° shouldbe achieved.

Refer to AN-1043 for more detailed compensation

techniques using Transconductance Amplifiers.

7. Place the second pole f

p2 at or near fesr of the out-

put capacitor C

o and determine the value of R21 from

equation (19). Make sure R

21 <

8. Use equation (24) to calculate R

5 = R2 x

(24)

The crossover frequency f

0 for Type III compensa-

tion is represented by equation (23):

Follow the steps below to determine the feedback

loop compensation component values:

1. Select a zero db crossover frequency f

0 in the range

of 10% to 20% of the switching frequency f

sw.

2. Select R

20~ 10kΩ

3. Place the first zero f

z1 at 75% of the resonant fre-

quency f

LC of the output filter.

Determine C

9 from equation (21).

4. Place a third pole f

P3 at or near the switching fre-

quency f

SW.

Select C7 such that C

7 <

5. Calculate C

8 from equation (23).

6. Place the second zero at 125% of the resonant

frequency f

LC of the output filter. Calculate R2 using

equation (22).

The frequencies of the three poles and the two zeros

of the Type III compensation scheme are represented

by the following equations:

p1= 0

(18)

(19)

(21)

(20)

ramp

(22)

(23)

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