IP1201PBF datasheet(21/29 Pages) IRF

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iP1201PbF

2. Select R

26 = ~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 (20).

4. Place a third pole f

P3 at or near the switching fre-

quency f

SW.

Select C22 such that C

22 <<

5. Calculate C

21 from equation (22).

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

quency f

LC of the output filter. Calculate R9 using equa-

tion (21).

7. Place the second pole f

p2 at or near fesr of the output

capacitor C

o and determine the value of R25 from equa-

tion (18). Make sure R

25 <

8. Use equation (23) 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.

Refer toAN-1043 for more detailed compensation tech-

niques using Transconductance Amplifiers.

Compensation in Current Share Mode

The iP1201PbF can be configured in single output par-

alleled configuration. The feedback loop of the first out-

put is closed around the output voltage, and the sec-

ond amplifier, which is also a transconductance one,

forces equal sharing of the inductor currents in both

outputs.

Voltage Loop

Type II and Type III methods of voltage loop compen-

sation discussed above, can be used to compensate

the voltage loop of a single output iP1201PbF. In this ,

Fig. 22: Output 2 error amplifier compensation net-

work for parallel configuration.

(23)

ref

−

Resistor R

6 of the compensation network is calculated

according to equation (24)

(24)

The power stage of the current loop has a dominant

pole at frequency expressed by equation (25):

⋅

where, R

eq represents the total resistance of the power

stage that includes the Rdson of the FET switches,

the DC resistance of the inductor and the shunt resis-

tance, and is expressed by equation (26):

use 10mohm for FET Rdson.

To calculate for C11, place the zero frequency fz at

10 times the dominant pole frequency f

p using equa-

tion (27):

= 10

(26)

(25)

(27)

ramp

dson

Select

11 ≤

Current Loop

Use the following procedure for current loop compen-

sation:

In Fig. 22, L

1 and L2 are the inductors for outputs 1 and

2 respectively. Rsh1 and Rsh2 are the current sensing

shunts for the same outputs.

case the total amount of capacitance seen by both

channels and the inductance of the voltage control-

ling channel should be considered for compensation.

E/A2

iP1201

C11

sh1

Rsh2

Vsw1

Vsw2

Vp-Ref

CC2

Load

FB2

VOUT

iP1201PbF

IP1201PBF Datasheet(PDF) 21 Page - International Rectifier

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