Fairchild FSQ500L, User Manual

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© 2011 Fairchild Semiconductor Corporation 3 FEBFSQ500L_H257v1 • Rev. 1.0.1
This user guide supports the evaluation kit for the FSQ500L. It should be used in
conjunction with the FSQ500L datasheet as well as Fairchild’s application notes and
technical support team. Please visit Fairchild’s website at
www.fairchildsemi.com .
1. Introduction
This engineering report describes a 2.04W power supply using a FSQ500L. This power
supply is targeted for a flyback converter replaces linear power supplies with low cost
and small size.
1.1. General Description
This device combines a current-mode Pulse Width Modulator (PWM) with a SenseFET
and high-voltage regulator connected from the DRAIN pin to supply the V
CC
. This device
does not need to use bias winding and associated external components.
Using a SOT-223 package, FSQ500L reduces total size and weight while increasing
efficiency, productivity, and system reliability. Using FSQ500L, this design example for
2.04W can be implemented with few external components and minimized cost.
1.2. Features

Single-Chip 700V SenseFET Power Switch

Precision Fixed Operating Frequency: 130kHz

No-load consumption 250mW at 265V
AC
with Burst Mode and Down to 60mW
with External Bias

Internal Startup Switch

Soft-Start Time Tuned by External Capacitor

Under-Voltage Lockout (UVLO) with Hysteresis

Pulse-by-Pulse Current Limit

Overload Protection (OLP) and Internal Thermal Shutdown Function (TSD) with
Hysteresis

Auto-Restart Mode

No Need for Auxiliary Bias Winding