NX2113 datasheet(12/19 Pages) MICROSEMI

12 / 19 page

NX2113/2113A

Rev. 2.0

11/18/05

40dB/decade

20dB/decade

loop gain

ESR

compensator

power stage

FZ1 Z2

FP2

Figure 10 - Bode plot of Type III compensator

Design example for type III compensator are in

order. Use the same power stage requirement as demo

board. The crossover frequency has to be selected as

LC<FO<FESR, and FO<=1/10~1/5Fs.

1.Calculate the location of LC double pole F

and ESR zero F

ESR.

OUT

0.78uH 660uF

7kHz

×π ××

ESR

OUT

ESRC

660uF

60kHz

×π ××

×π ×

Ω×

2.Set R

2 equal to10kΩ, then R1= 10kΩ.

3. Set zero F

Z2 = FLC and Fp1 =FESR .

4. Calculate R

4 and C3 with the crossover frequency

Choose C

2=2.7nF.

6. Calculate C

1 by equation (14) with pole Fp2 at

half the swithing frequency.

11k

300kHz

48pF

×π ××

×π ×

Ω×

Choose C

1=47pF.

7. Calculate R

3 by equation (13).

P13

60kHz 2.2nF

1.2k

×π ××

=Ω

Choose R

3=1.2kΩ.

smaller than 1/10~ 1/5 of the switching frequency. Set

O=45kHz.

C =

(-)

(

10k

7kHz 60kHz

=2nF

×π×

×π ×Ω

OSCO

out

in3

R =C

45kHz 0.78uH

660uF

12V

2.2nF

=11k

×π ××

××

×π××

××

Ω

Choose C

3=2.2nF, R4=11kΩ.

5. Calculate C

2 with zero Fz1 at 75% of the LC

double pole by equation (11).

Z14

0.75

7kHz

11k

2.75nF

×π ××

×π ×

×Ω

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