Data Sheet

© 2009 Fairchild Semiconductor Corporation www.fairchildsemi.com
FSL136MR • Rev. 1.0.7 3
FSL136MR — Green Mode Fairchild Power Switch (FPS™)
Pin Configuration
Figure 3. Pin Configuration
Pin Definitions
Pin # Name
Description
1 GND
Ground. SenseFET source terminal on the 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). Once
V
CC
reaches the UVLO upper threshold (12V), the internal startup switch opens and device
power is supplied via the auxiliary transformer winding.
3 V
FB
Feedback Voltage. The non-inverting input to the PWM comparator, it has a 0.4mA current
source connected internally, while a capacitor and opto-coupler are typically connected
externally. There is a delay while charging external capacitor C
FB
from 2.4V to 6V using an
internal 5µA current source. This delay prevents false triggering under transient conditions, but
still allows the protection mechanism to operate under true overload conditions.
4 I
PK
Peak Current Limit. Adjusts the peak current limit of the SenseFET. The feedback 0.4mA
current source is diverted to the parallel combination of an internal 6k resistor and any
external resistor to GND on this pin to determine the peak current limit.
5 V
STR
Startup. Connected 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 V
CC
reaches 12V, the internal switch is opened.
6, 7, 8 Drain
Drain. Designed to connect directly to the primary lead of the transformer and capable of
switching a maximum of 650V. Minimizing the length of the trace connecting these pins to the
transformer decreases leakage inductance.