ACT4501 データシートの表示（PDF） - Active-Semi, Inc
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ACT4501 Datasheet PDF : 16 Pages
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ACT4501
Rev 2, 14-Nov-12
STABILITY COMPENSATION CONT’D
feedback resistance values for cable compensation.
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 6, adding a
capacitor in paralled with RFB1 or increasing the
compensation capacitance at COMP pin helps the
system stability.
Figure 5:
Cable Compensation at Various Resistor Divider
Values
Delta Output Voltage vs. Output Current
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 7 shows an example of PCB layout.
0.3
0.25
VIN = 12V
V0UT = 5V
0.2
0.15
0.1
R FB1
=
300k
= 270k
R FB1
=
240k
R FB1
= 200k
R FB1
RFB1 = 150k
0.05
0
0
RFB1 = 100k
RFB1 = 51k
200
400
600
800
1000
Output Current (mA)
Figure 6:
Frequency Compensation for High RFB1
Figure 7: PCB Layout
Figure 8 gives one typical car charger application
schematics and associated BOM list.
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.
Innovative PowerTM
-9-
www.active-semi.com
Copyright © 2012 Active-Semi, Inc.
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