ACT4513
Active- Semi
Rev 6, 29-Jul-11
STABILITY COMPENSATION CONT’D
RFB1 is the high side resistor of voltage divider.
close to IN pin as possible. CIN is connected
power GND with vias or short and wide path.
In the case of high RFB1 used, the frequency
compensation
needs
to
be
adjusted
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.
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.
4) Use copper plane for power GND for best heat
dissipation and noise immunity.
Figure 6:
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.
Cable Compensation at Various Resistor Divider
Values
Delta Output Voltage vs. Output Current
450
400
350
300
250
200
150
100
50
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
Figure 9 and Figure 10 give two 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.
2) Place input decoupling ceramic capacitor CIN as
Innovative PowerTM
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