FSQ0765RQ — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
April 2009
FSQ0765RQ
Green-Mode Fairchild Power Switch (FPS™) for
Quasi-Resonant Operation -
Low EMI and High Efficiency
Features
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Optimized for Quasi-Resonant Converter (QRC)
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Low EMI through Variable Frequency Control and AVS
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Description
A Quasi-Resonant Converter (QRC) generally shows
lower EMI and higher power conversion efficiency than a
conventional hard-switched converter with a fixed
switching frequency. The FSQ-series is an integrated
Pulse-Width Modulation (PWM) controller and
SenseFET specifically designed for quasi-resonant
operation and Alternating Valley Switching (AVS). The
PWM controller includes an integrated fixed-frequency
oscillator, Under-Voltage Lockout (UVLO), Leading-
Edge Blanking (LEB), optimized gate driver, internal soft-
start, temperature-compensated precise current sources
for a loop compensation, and self-protection circuitry.
Compared with a discrete MOSFET and PWM controller
solution, the FSQ-series can reduce total cost,
component count, size, and weight; while simultaneously
increasing efficiency, productivity, and system reliability.
This device provides a basic platform that is well suited
for cost-effective designs of quasi-resonant switching
flyback converters.
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(Alternating Valley Switching)
High-Efficiency through Minimum Voltage Switching
Narrow Frequency Variation Range over Wide Load
and Input Voltage Variation
Advanced Burst-Mode Operation for Low Standby
Power Consumption
Simple Scheme for Sync Voltage Detection
Pulse-by-Pulse Current Limit
Various Protection functions: Overload Protection
(OLP), Over-Voltage Protection (OVP), Abnormal
Over-Current Protection (AOCP), Internal Thermal
Shutdown (TSD) with Hysteresis, Output Short
Protection (OSP)
Under-Voltage Lockout (UVLO) with Hysteresis
Internal Startup Circuit
Internal High-Voltage Sense FET (650V)
Built-in Soft-Start (17.5ms)
Applications
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Power Supply for LCD TV and Monitor, VCR, SVR,
STB, and DVD & DVD Recorder
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Adapter
Related Resources
Visit
http://www.fairchildsemi.com/apnotes/
for:
!
AN-4134: Design Guidelines for Offline Forward
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Converters Using Fairchild Power Switch (FPS
™
)
AN-4137: Design Guidelines for Offline Flyback
Converters Using Fairchild Power Switch (FPS
™
)
AN-4140: Transformer Design Consideration for
Offline Flyback Converters Using Fairchild Power
Switch (FPS
™
)
AN-4141: Troubleshooting and Design Tips for
Fairchild Power Switch (FPS
™
) Flyback Applications
AN-4145: Electromagnetic Compatibility for Power
Converters
AN-4147: Design Guidelines for RCD Snubber of
Flyback
AN-4148: Audible Noise Reduction Techniques for
Fairchild Power Switch Fairchild Power Switch(FPS
™)
Applications
AN-4150: Design Guidelines for Flyback Converters
Using FSQ-Series Fairchild Power Switch (FPS
™
)
© 2008 Fairchild Semiconductor Corporation
FSQ0765RQ Rev. 1.0.1
www.fairchildsemi.com
FSQ0765RQ — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
Pin Configuration
6. V
str
5. Sync
4. FB
3. V
CC
2. GND
1. Drain
FSQ0765R Rev.00
Figure 3. Pin Configuration (Top View)
Pin Definitions
Pin #
1
2
3
Name
Drain
GND
V
CC
Description
SenseFET drain.
High-voltage power SenseFET drain connection.
Ground.
This pin is the control ground and the SenseFET source.
Power Supply.
This pin is the positive supply input. This pin provides internal operating current for
both startup and steady-state operation.
Feedback.
This pin is internally connected to the inverting input of the PWM comparator. The
collector of an opto-coupler is typically tied to this pin. For stable operation, a capacitor should be
placed between this pin and GND. If the voltage of this pin reaches 6V, the overload protection
triggers, which shuts down the FPS.
Sync.
This pin is internally connected to the sync-detect comparator for quasi-resonant switching.
In normal quasi-resonant operation, the threshold of the sync comparator is 1.2V/1.0V.
Startup.
This pin is connected directly, or through a resistor, to the high-voltage DC link. At
start-up, the internal high-voltage current source supplies internal bias and charges the external
capacitor connected to the V
CC
pin. Once V
CC
reaches 12V, the internal current source is disabled.
It is not recommended to connect V
str
and Drain together.
4
FB
5
Sync
6
V
str
© 2008 Fairchild Semiconductor Corporation
FSQ0765RQ Rev. 1.0.1
4
www.fairchildsemi.com
FSQ0765RQ — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
Absolute Maximum Ratings
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be opera-
ble above the recommended operating conditions and stressing the parts to these levels is not recommended. In addi-
tion, extended exposure to stresses above the recommended operating conditions may affect device reliability. The
absolute maximum ratings are stress ratings only. T
A
= 25°C, unless otherwise specified.
Symbol
V
str
V
DS
V
CC
V
FB
V
Sync
I
DM
I
D
E
AS
P
D
T
J
T
A
T
STG
ESD
V
str
Pin Voltage
Drain Pin Voltage
Supply Voltage
Parameter
Min.
500
650
Max.
Unit
V
V
20
-0.3
-0.3
T
C
= 25°C
T
C
= 100°C
13.0
13.0
14.4
3.6
2.28
570
45
Internally limited
-25
-55
Human Body Model
Charged Device Model
2
2
+85
+150
V
V
V
A
A
mJ
W
°C
°C
°C
kV
Feedback Voltage Range
Sync Pin Voltage
Drain Current Pulsed
Continuous Drain Current
(6)
Single Pulsed Avalanche Energy
(7)
Total Power Dissipation(Tc=25°C)
Operating Junction Temperature
Operating Ambient Temperature
Storage Temperature
Electrostatic Discharge Capability
Notes:
6. Repetitive rating: Pulse width limited by maximum junction temperature.
7. L=81mH, starting T
J
=25°C.
Thermal Impedance
T
A
= 25°C unless otherwise specified.
Symbol
θ
JA
θ
JC
Parameter
Junction-to-Ambient Thermal Resistance
(8)
Junction-to-Case Thermal Resistance
(9)
Value
50
2.8
Unit
°
C/W
°
C/W
Notes:
8. Free standing with no heat-sink under natural convection.
9. Infinite cooling condition - refer to the SEMI G30-88.
© 2008 Fairchild Semiconductor Corporation
FSQ0765RQ Rev. 1.0.1
5
www.fairchildsemi.com
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