ACT4060A

Rev 1, 25-Jun-09

Innovative Power

TM

- 6 -

www.active-semi.com

Copyright © 2009 Active-Semi, Inc.

2.5V

22μF Ceramic

8.2kΩ

2.2nF

3.3V

22μF Ceramic

12kΩ

1.5nF

5V

22μF Ceramic

15kΩ

1.5nF

2.5V

47μF SP CAP

15kΩ

1.5nF

3.3V

47μF SP CAP

15kΩ

1.8nF

5V

47μF SP CAP

15kΩ

2.7nF

2.5V

470μF/6.3V/30mΩ

15kΩ

15nF

3.3V

470μF/6.3V/30mΩ

15kΩ

22nF

5V

470μF/6.3V/30mΩ

15kΩ

27nF

(12)

(Ω)

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

×

×

≥

−

OUT

OUT

6

ESRCOUT

V

012

.

0

,

C

10

1

.

1

Min

R

OUT

OUT

5

COMP

C

V

10

2

.

1

C

−

×

=

(F)

(11)

(10)

(F)

COMP

5

COMP

R

10

8

.

1

C

−

×

=

(9)

(Ω)

OUT

OUT

8

C

V

10

7

.

1

×

=

V

3

.

1

G

G

10

f

C

V

π

2

R

COMP

EA

SW

OUT

OUT

COMP

×

=

(7)

COMP

COMP

1

Z

C

R

2

1

f

π

=

(6)

OUT

OUT

OUT

2

P

C

V

π

2

I

f

=

(4)

COMP

VEA

OUT

VDC

G

A

I

V

3

.

1

A

=

COMP

ACT4060A

COMP

ESRCOUT

OUT

2

COMP

R

R

C

C

=

(13)

COMP2

COMP

3

P

C

R

π

2

1

f

=

(8)

(5)

COMP

VEA

EA

1

P

C

A

π

2

G

f

=

STABILITY COMPENSATION

Figure 2:

Stability Compensation

The feedback loop of the IC is stabilized by the

components at the COMP pin, as shown in Figure

2. The DC loop gain of the system is determined by

the following equation:

The second pole P2 is the output pole:

The following steps should be used to compensate

the IC:

STEP 1. Set the cross over frequency at 1/10 of the

STEP 3. If the output capacitor’s ESR is high

enough to cause a zero at lower than 4 times the

cross over frequency, an additional compensation

capacitor has sufficiently low ESR, a small value

PCB layout parasitic effects.

Table 2 shows some calculated results based on

the compensation method above.

Table 2:

Typical Compensation for Different Output

Voltages and Output Capacitors

Figure 4 shows an example ACT4060A application circuit

generating a 3.3V/2A output.