ACT4523

Rev 7, 01-Aug-13

Innovative Power

TM

- 8 -

www.active-semi.com

Copyright © 2013 Active-Semi, Inc.

2.5V

47μF Ceramic CAP

5.6kΩ

3.3nF

None

3.3V

47μF Ceramic CAP

6.2kΩ

3.3nF

None

5V

47μF Ceramic CAP

8.2kΩ

3.3nF

None

2.5V

470μF/6.3V/30mΩ

39kΩ

22nF

47pF

3.3V

470μF/6.3V/30mΩ

45kΩ

22nF

47pF

5V

470μF/6.3V/30mΩ

51kΩ

22nF

47pF

(15)

(Ω)

(16)

COMP

ESRCOUT

OUT

2

COMP

R

R

C

C

=

OUT

OUT

6

COMP

C

V

10

45

.

6

C

_

×

=

(F)

(14)

(13)

(F)

COMP

5

COMP

R

10

83

.

2

C

×

=

(12)

(Ω)

OUT

OUT

7

C

V

10

12

.

5

×

=

V

808

.

0

G

G

10

f

C

V

2

R

COMP

EA

SW

OUT

OUT

COMP

×

=

π

(11)

COMP2

COMP

3

P

C

R

π

2

1

f

=

(10)

COMP

COMP

1

Z

C

R

π

2

1

f

=

(9)

OUT

OUT

OUT

2

P

C

V

π

2

I

f

=

(8)

(7)

COMP

VEA

OUT

VDC

G

A

I

V

808

.

0

A

=

STABILITY COMPENSATION

Figure 5:

Stability Compensation

The feedback loop of the IC is stabilized by the

components at the COMP pin, as shown in Figure

5. 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 1 shows some calculated results based on

the compensation method above.

Table 1:

Typical Compensation for Different Output

Voltages and Output Capacitors

CC Loop Stability

The constant-current control loop is internally

compensated over the 1500mA-3000mA output

range. No additional external compensation is

required to stabilize the CC current.

Output Cable Resistance Compensation

To compensate for resistive voltage drop across the

charger's output cable, the ACT4523 integrates a

simple, user-programmable cable voltage drop

compensation using the impedance at the FB pin.

Use the curve in Figure 6 to choose the proper

feedback resistance values for cable compensation.

COMP

VEA

EA

1

P

C

A

π

2

G

f

=

(

)

OUT

OUT

ESRCOUT

V

006

.

0

,

C

10

77

.

1

Min

R

6

_

×

×

≥