Data Sheet

© 2007 Fairchild Semiconductor Corporation www.fairchildsemi.com
FSQ100 Rev. 1.0.2 3
FSQ100 — Green Mode Fairchild Power Switch (FPS
TM
)
Pin Assignments
Figure 3. Pin Configuration (Top View)
Pin Definitions
Pin # Name Description
1 GND
Ground. SenseFET source terminal on primary-side and internal control ground.
2 V
CC
Positive Supply Voltage Input. Although connected to an auxiliary transformer winding,
current is supplied from pin 5 (V
STR
) via an internal switch during startup (see Figure 2). When
V
CC
reaches the UVLO upper threshold (9V), the internal startup switch opens and device power
is supplied via the auxiliary transformer winding.
3 V
FB
Feedback. Inverting input to the PWM comparator with its normal input level lies between 0.5V
and 2.5V. It has a 0.4mA current source connected internally, while a capacitor and opto-
coupler are typically connected externally. A feedback voltage of 4.5V triggers overload
protection (OLP). There is a time delay while charging external capacitor C
fb
from 3V to 4.5V
using an internal 5µA current source. This time delay prevents false triggering under transient
conditions, but still allows the protection mechanism to operate in true overload conditions.
4 NC
No Connection.
5 V
STR
Startup. This pin connects directly to the rectified AC line voltage source. At startup, the internal
switch supplies internal bias and charges an external storage capacitor placed between the V
CC
pin and ground. Once the V
CC
reaches 9V, the internal switch stops charging the capacitor.
6,7,8 Drain
SenseFET Drain. The drain pins are designed to connect directly to the primary lead of the
transformer and are capable of switching a maximum of 650V. Minimizing the length of the trace
connecting these pins to the transformer decreases leakage inductance.
1
2
3
45
6
7
8GND
V
CC
V
FB
NC
V
STR
D
r
ain
D
r
ain
D
r
ain