SG6902 Fairchild Semiconductor, SG6902 Datasheet - Page 19

• Manufacturer Part Number: SG6902
• Description: Green-Mode PFC / Flyback-PWM Controller
• Manufacturer: Fairchild Semiconductor

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Green-Mode PFC / Flyback-PWM Controller
PCB Layout
SG6902 has two ground pins. Good high-frequency or RF
layout practices should be followed. Avoid long PCB
traces and component leads. Locate decoupling capacitors
near the SG6902. A resistor (5 ~ 20Ω) is recommended,
connected in series from the OPFC and OPWM, to the
gate of the MOSFET.
Isolating the interference between the PFC and PWM
stages is also important. Figure 10 shows an example of
the PCB layout. The ground trace connected from the
AGND pin to the decoupling capacitor should be low
impedance and as short as possible. The ground trace 1
provides a signal ground and should be connected directly
to the decoupling capacitor V
The ground trace 2 shows that the AGND pins should
connect to the PFC output capacitor C
© System General Corp.
Version 1.3.1 (IAO33.0022.B3)
DD
and/or to the AGND pin.
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independently.
Fig.10 Layout Considerations
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The ground trace 3 is independently tied from the PGND
to the PFC output capacitor C
capacitor C
switching. To provide a good ground reference and
reduce switching noise of both the PFC and PWM stages,
the ground traces 6 and 7 should be located very near and
be low impedance.
The IPFC pin is connected directly to R
improve noise immunity (do not incorrectly connect to
ground trace 2). The IMP and ISENSE pins should be
connected directly via the resistors R
terminal of R
and PWM stages of the current loop, they should be as
short as possible.
O
S
www.sg.com.tw • www.fairchildsemi.com
. Because the ground trace 4 and 5 are PFC
is the major ground reference for power
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. The ground in the output
Product Specification
2
and R
September, 2007
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through R
P
to another
SG6902
3
to