Pin Configuration
Figure 3. Package Diagram
Pin Definitions
Pin #
Name
Description
1
VDL
This is the drain of the high-side MOSFET, typically connected to the input DC link voltage.
This pin is for discharging the external soft-start capacitor when any protections are
triggered. When the voltage of this pin drops to 0.2V, all protections are reset and the
controller starts to operate again.
2
AR
This pin programs the switching frequency. Typically, an opto-coupler is connected to control
the switching frequency for the output voltage regulation.
3
4
RT
This pin senses the current flowing through the low-side MOSFET. Typically, negative
voltage is applied on this pin.
CS
5
6
SG
PG
This pin is the control ground.
This pin is the power ground. This pin is connected to the source of the low-side MOSFET.
This pin is the supply voltage of the control IC.
7
LVCC
NC
8
No connection.
9
HVCC
VCTR
This is the supply voltage of the high-side gate-drive circuit IC.
This is the drain of the low-side MOSFET. Typically, a transformer is connected to this pin.
10
© 2010 Fairchild Semiconductor Corporation
FSFR-XS Series • Rev.1.0.1
www.fairchildsemi.com
3
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