ACT4515SH-T Ver la hoja de datos (PDF) - Active-Semi, Inc
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ACT4515SH-T Datasheet PDF : 16 Pages
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ACT4515
Rev 6, 14-Nov-12
STABILITY COMPENSATION CONT’D
simple, user-programmable cable voltage drop
compensation using the impedance at the FB pin.
Use the curve in Figure 5 to choose the proper
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 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
0.64
0.56
0.48
VIN = 14V
V0UT = 5V
IISET = 1.5A
0.4
0.32
0.24
0.16
0.08
= 300k
R FB1
= 240k
RFB1 = 200k
R FB1
RFB1
=
150k
RFB1 = 100k
RFB1 = 68k
RFB1 = 12k
0
0
250
500
750 1000 1250 1500
Output Current (mA)
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
7) Reduce SW Pad Size
Figure 8 shows an example of PCB layout.
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
Figure 9 and Figure 10 give two typical car charger
application schematics and associated BOM list.
Innovative PowerTM
-9-
www.active-semi.com
Copyright © 2012 Active-Semi, Inc.
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