ACT4523 データシートの表示（PDF） - Active-Semi, Inc

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ACT4523

Wide-Input Sensorless CC/CV Step-Down DC/DC Converter

Active-Semi, Inc 

ACT4523

Rev 7, 01-Aug-13

STABILITY COMPENSATION CONT’D

RFB1 is the high side resistor of voltage divider.

In the case of high RFB1 used, the frequency

compensation needs to be 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

Delta Output Voltage vs. Output Current

350

300

= 430k

RFB1 = 360k

250

RFB1 = 300k

200

RFB1 = 240k

150

100

RRRFBFF1BB11==125000kk

RFB1 = 100k

50

RFB1 = 51k

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. Connect

exposed pad to power ground copper area with

copper and vias.

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.

0

0

0.4

0.8

1.2

1.6

2

Output Current (A)

Figure 7:

Frequency Compensation for High RFB1

Figure 8: PCB Layout

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

Figure 9 gives one typical car charger application

schematic and associated BOM list.

Innovative PowerTM

-9-

www.active-semi.com

Copyright © 2013 Active-Semi, Inc.

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