ACT4513 datasheet(9/15 Pages) ACTIVE-SEMI

9 / 15 page

ACT4513

Rev 6, 29-Jul-11

Active-Semi

Innovative Power

- 9 -

www.active-semi.com

STABILITY COMPENSATION CONT’D

RFB1 is the high side resistor of voltage divider.

In the case of high RFB1 used, the frequency

compensation

needs

adjusted

correspondingly. As show in Figure 7, adding a

capacitor in paralled with RFB1 or increasing the

compensation capacitance at COMP pin helps the

system stability.

Figure 6:

Cable Compensation at Various Resistor Divider

Values

Figure 7:

Frequency Compensation for High RFB1

PC Board Layout Guidance

When laying out the printed circuit board, the

following checklist should be used to ensure proper

operation of the IC.

1) Arrange the power components to reduce the

AC loop size consisting of CIN, IN pin, SW pin

and the schottky diode.

2) Place input decoupling ceramic capacitor CIN as

close to IN pin as possible. CIN is connected

power GND with vias or short and wide path.

3) Return FB, COMP and ISET to signal GND pin,

and connect the signal GND to power GND at a

single point for best noise immunity.

4) Use copper plane for power GND for best heat

dissipation and noise immunity.

5) Place feedback resistor close to FB pin.

6) Use short trace connecting HSB-CHSB-SW loop

Figure 8 shows an example of PCB layout.

Figure 9 and Figure 10 give two typical car charger

application schematics and associated BOM list.

Delta Output Voltage vs. Output Current

300

250

200

150

100

350

400

450

Output Current (A)

0.4

0.8

1.2

1.6

= 3

RFB

= 2

RFB1

= 150

RFB

1 =

200

RFB1 =

100k

= 3

RFB1 =

51k

= 4

30k

Figure 8: PCB Layout

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