IP1201 datasheet(21/29 Pages) IRF

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iP1201

The crossover frequency f

0 for type III compensation

is represented by equation (22):

(22)

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

26 = ~1kΩ

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 (20).

4. Select C22 such that

Doing so will place a third pole f

P3 at or near half the

switching frequency f

SW.

5. Calculate C

21 from equation (22).

6. Place the second pole f

p2 at fesr of the output ca-

pacitor C

o and determine the value of R25 from equa-

tion (18).

7. Place the second zero near the resonant frequency

LC of the output filter. Calculate R9 using equation

(21).

8. Use equation (1) to calculate R

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 stabil-

ity a phase margin greater than 45° should be

achieved.

If the iP1201 is configured in single output paral-

leled configuration, the feedback loop of the first

output is closed around the output voltage, and the

second amplifier, which is also a transconductance

one, forces equal sharing of the inductor currents in

both outputs.

In Fig. 22, L

1 and L2 are the inductors for outputs 1

and 2 respectively. Rsh1 and Rsh2 are the current

E/A2

iP1201

C11

sh1

Rsh2

Vsw1

Vsw2

Vp-Ref

CC2

Load

FB2

VOUT

Fig. 22: Output 2 error amplifier compensation net-

work for parallel configuration.

For type II compensation scheme resistor R

6 is cal-

culated according to equation (23)

out

−

(23)

where, f

02 is the desired zero crossover frequency.

The zero frequency f

z of the compensation network

is expressed in equation (24)

(24)

and should be placed near half the output2 reso-

nant frequency f

LC2.

A value for C

11 is calculated by using equations (23),

(24) and (25).

(25)

≤

sensing shunts for the same outputs.

Vin

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