© 2007 Fairchild Semiconductor Corporation

www.fairchildsemi.com

FSQ100 Rev. 1.0.2

3

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

Positive Supply Voltage Input

. Although connected to an auxiliary transformer winding,

is supplied via the auxiliary transformer winding.

3

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

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

Startup

. This pin connects directly to the rectified AC line voltage source. At startup, the internal

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

8

GND

NC

Drain

Drain

Drain