October 2010
© 2010 Fairchild Semiconductor Corporation www.fairchildsemi.com
FSFR-XS Series • Rev.1.0.1
FSFR-XS Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter
FSFR-XS Series — Fairchild Power Switch (FPS™)
for Half-Bridge Resonant Converters
Features
Variable Frequency Control with 50% Duty Cycle
for Half-Bridge Resonant Converter Topology
High Efficiency through Zero Voltage Switching (ZVS)
Internal UniFET™ with Fast-Recovery Body Diode
Fixed Dead Time (350ns) Optimized for MOSFETs
Up to 300kHz Operating Frequency
Auto-Restart Operation for All Protections with
External LVCC
Protection Functions: Over-Voltage Protection
(OVP), Over-Current Protection (OCP), Abnormal
Over-Current Protection (AOCP), Internal Thermal
Shutdown (TSD)
Applications
PDP and LCD TVs
Desktop PCs and Servers
Adapters
Telecom Power Supplies
Description
The FSFR-XS series includes highly integrated power
switches designed for high-efficiency half-bridge
resonant converters. Offering everything necessary to
build a reliable and robust resonant converter, the FSFR-
XS series simplifies designs while improving productivity
and performance. The FSFR-XS series combines power
MOSFETs with fast-recovery type body diodes, a high-
side gate-drive circuit, an accurate current controlled
oscillator, frequency limit circuit, soft-start, and built-in
protection functions. The high-side gate-drive circuit has
common-mode noise cancellation capability, which
guarantees stable operation with excellent noise
immunity. The fast-recovery body diode of the MOSFETs
improves reliability against abnormal operation
conditions, while minimizing the effect of reverse
recovery. Using the zero-voltage-switching (ZVS)
technique dramatically reduces the switching losses and
significantly improves efficiency. The ZVS also reduces
the switching noise noticeably, which allows a small-
sized Electromagnetic Interference (EMI) filter.
The FSFR-XS series can be applied to resonant
converter topologies such as series resonant, parallel
resonant, and LLC resonant converters.
Related Resources
AN4151 — Half-bridge LLC Resonant Converter Design
Using FSFR-Series Fairchild Power Switch (FPSTM)
Ordering Information
Part Number Package Operating
Junction
Temperature RDS(ON_MAX) Maximum Output Power
without Heatsink
(VIN=350~400V)(1,2)
Maximum Output
Power with Heatsink
(VIN=350~400V)(1,2)
FSFR2100XS
9-SIP
-40 to +130°C
0.51Ω 180W 400W
FSFR1800XS 0.95Ω 120W 260W
FSFR1700XS 1.25Ω 100W 200W
FSFR1600XS 1.55Ω 80W 160W
FSFR2100XSL
9-SIP
L-Forming
0.51Ω 180W 400W
FSFR1800XSL 0.95Ω 120W 260W
FSFR1700XSL 1.25Ω 100W 200W
FSFR1600XSL 1.55Ω 80W 160W
Notes:
1. The junction temperature can limit the maximum output power.
2. Maximum practical continuous power in an open-frame design at 50°C ambient.
© 2010 Fairchild Semiconductor Corporation www.fairchildsemi.com
FSFR-XS Series • Rev.1.0.1 2
FSFR-XS Series — Fairchild Power Switch (FPS™) for Hal f-Bri dge Resonant Converter
Application Circuit Diagram
Figure 1. Typical Application Circuit (LLC Resonant Half-Bridge Converter)
Block Diagram
Figure 2. Internal Block Diagram
© 2010 Fairchild Semiconductor Corporation www.fairchildsemi.com
FSFR-XS Series • Rev.1.0.1 3
FSFR-XS Series — Fairchild Power Switch (FPS™) for Hal f-Bri dge Resonant Converter
Pin Configuration
Figure 3. Package Diagram
Pin Definitions
Pin # Name Description
1 VDL This is the drain of the high-side MOSFET, typically connected to the input DC link voltage.
2 AR
This pin is for discharging the external soft-start capacitor when any protections are
triggered. When the voltage of this pin drops to 0.2V, all protections are reset and the
controller starts to operate again.
3 RT This pin programs the switching frequency. Typically, an opto-coupler is connected to control
the switching frequency for the output voltage regulation.
4 CS
This pin senses the current flowing through the low-side MOSFET. Typically, negative
voltage is applied on this pin.
5 SG This pin is the control ground.
6 PG This pin is the power ground. This pin is connected to the source of the low-side MOSFET.
7 LVCC This pin is the supply voltage of the control IC.
8 NC No connection.
9 HVCC This is the supply voltage of the high-side gate-drive circuit IC.
10 VCTR This is the drain of the low-side MOSFET. Typically, a transformer is connected to this pin.
© 2010 Fairchild Semiconductor Corporation www.fairchildsemi.com
FSFR-XS Series • Rev.1.0.1 4
FSFR-XS Series — Fairchild Power Switch (FPS™) for Hal f-Bri dge Resonant Converter
Absolute Maximum Ratings
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be
operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In
addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The
absolute maximum ratings are stress ratings only. TA=25°C unless otherwise specified.
Symbol Parameter Min. Max. Unit
VDS Maximum Drain-to-Source Voltage (VDL-VCTR and VCTR-PG) 500 V
LVCC Low-Side Supply Voltage -0.3 25.0 V
HVCC to VCTR High-Side VCC Pin to Low-Side Drain Voltage -0.3 25.0 V
HVCC High-Side Floating Supply Voltage -0.3 525.0 V
VAR Auto-Restart Pin Input Voltage -0.3 LVCC V
VCS Current-Sense (CS) Pin Input Voltage -5.0 1.0 V
VRT R
T Pin Input Voltage -0.3 5.0 V
dVCTR/dt Allowable Low-Side MOSFET Drain Voltage Slew Rate 50 V/ns
PD Total Power Dissipation(3)
FSFR2100XS/L 12.0
W
FSFR1800XS/L 11.7
FSFR1700XS/L 11.6
FSFR1600XS/L 11.5
TJ Maximum Junction Temperature(4) +150
°C
Recommended Operating Junction Temperature(4) -40 +130
TSTG Storage Temperature Range -55 +150 °C
MOSFET Section
VDGR Drain Gate Voltage (RGS=1MΩ) 500 V
VGS Gate Source (GND) Voltage ±30 V
IDM Drain Current Pulsed(5)
FSFR2100XS/L 32
A
FSFR1800XS/L 23
FSFR1700XS/L 20
FSFR1600XS/L 18
ID Continuous Drain Current
FSFR2100XS/L TC=25°C 10.5
A
TC=100°C 6.5
FSFR1800XS/L TC=25°C 7.0
TC=100°C 4.5
FSFR1700XS/L TC=25°C 6.0
TC=100°C 3.9
FSFR1600XS/L TC=25°C 4.5
TC=100°C 2.7
Package Section
Torque Recommended Screw Torque 5~7 kgf·cm
Notes:
3. Per MOSFET when both MOSFETs are conducting.
4. The maximum value of the recommended operating junction temperature is limited by thermal shutdown.
5. Pulse width is limited by maximum junction temperature.
© 2010 Fairchild Semiconductor Corporation www.fairchildsemi.com
FSFR-XS Series • Rev.1.0.1 5
FSFR-XS Series — Fairchild Power Switch (FPS™) for Hal f-Bri dge Resonant Converter
Thermal Impedance
TA=25°C unless otherwise specified.
Symbol Parameter Value Unit
θJC Junction-to-Case Center Thermal Impedance
(Both MOSFETs Conducting)
FSFR2100XS/L 10.44
ºC/W
FSFR1800XS/L 10.68
FSFR1700XS/L 10.79
FSFR1600XS/L 10.89
Electrical Characteristics
TA=25°C unless otherwise specified.
Symbol Parameter Test Conditions Min. Typ. Max. Unit
MOSFET Section
BVDSS Drain-to-Source Breakdown Voltage
ID=200μA, TA=25°C 500
V
ID=200μA, TA=125°C 540
RDS(ON) On-State Resistance
FSFR2100XS/L VGS=10V, ID=6.0A 0.41 0.51
Ω
FSFR1800XS/L VGS=10V, ID=3.0A 0.77 0.95
FSFR1700XS/L VGS=10V, ID=2.0A 1.00 1.25
FSFR1600XS/L VGS=10V, ID=2.25A 1.25 1.55
trr Body Diode Reverse
Recovery Time(6)
FSFR2100XS/L VGS=0V, IDiode=10.5A,
dIDiode/dt=100A/μs 120
ns
FSFR1800XS/L VGS=0V, IDiode=7.0A,
dIDiode/dt=100A/μs 160
FSFR1700XS/L VGS=0V, IDiode=6.0A,
dIDiode/dt=100A/μs 160
FSFR1600XS/L VGS=0V, IDiode=4.5A,
dIDiode/dt=100A/μs 90
Supply Section
ILK Offset Supply Leakage Current HVCC=VCTR=500V 50 μA
IQHVCC Quiescent HVCC Supply Current (HVCCUV+) - 0.1V 50 120 μA
IQLVCC Quiescent LVCC Supply Current (LVCCUV+) - 0.1V 100 200 μA
IOHVCC Operating HVCC Supply Current
(RMS Value)
fOSC=100KHz 6 9 mA
No Switching 100 200 μA
IOLVCC Operating LVCC Supply Current
(RMS Value)
fOSC=100KHz 7 11 mA
No Switching 2 4 mA
Continued on the foll owing page…
© 2010 Fairchild Semiconductor Corporation www.fairchildsemi.com
FSFR-XS Series • Rev.1.0.1 6
FSFR-XS Series — Fairchild Power Switch (FPS™) for Hal f-Bri dge Resonant Converter
Electrical Characteristics (Continued)
TA=25°C unless otherwise specified.
Symbol Parameter Test Conditions Min. Typ. Max. Unit
UVLO Section
LVCCUV+ LVCC Supply Under-Voltage Positive Going Threshold (LVCC Start) 11.2 12.5 13.8 V
LVCCUV- LVCC Supply Under-Voltage Negative Going Threshold (LVCC Stop) 8.9 10.0 11.1 V
LVCCUVH LVCC Supply Under-Voltage Hysteresis 2.50 V
HVCCUV+ HVCC Supply Under-Voltage Positive Going Threshold (HVCC Start) 8.2 9.2 10.2 V
HVCCUV- HVCC Supply Under-Voltage Negative Going Threshold (HVCC Stop) 7.8 8.7 9.6 V
HVCCUVH HVCC Supply Under-Voltage Hysteresis 0.5 V
Oscillator & Feedback Section
VRT V-I Converter Threshold Voltage
RT=5.2KΩ
1.5 2.0 2.5 V
fOSC Output Oscillation Frequency 94 100 106 KHz
DC Output Duty Cycle 48 50 52 %
fSS Internal Soft-Start Initial Frequency fSS=fOSC+40kHz,
RT=5.2KΩ
140 KHz
tSS Internal Soft-Start Time 2 3 4 ms
Protection Section
VCssH Beginning Voltage to Discharge CSS 0.9 1.0 1.1 V
VCssL Beginning Voltage to Charge CSS and
Restart 0.16 0.20 0.24 V
VOVP LVCC Over-Voltage Protection LVCC > 21V 21 23 25 V
VAOCP AOCP Threshold Voltage -1.0 -0.9 -0.8 V
tBAO AOCP Blanking Time(6) V
CS < VAOCP 50 ns
VOCP OCP Threshold Voltage -0.64 -0.58 -0.52 V
tBO OCP Blanking Time(6) V
CS < VOCP 1.0 1.5 2.0 μs
tDA Delay Time (Low Side) Detecting from
VAOCP to Switch Off(6) 250 400 ns
TSD Thermal Shutdown Temperature(6) 120 135 150
°C
Dead-Time Control Section
DT Dead Time(7) 350 ns
Notes:
6. This parameter, although guaranteed, is not tested in production.
7. These parameters, although guaranteed, are tested only in EDS (wafer test) process.
© 2010 Fairchild Semiconductor Corporation www.fairchildsemi.com
FSFR-XS Series • Rev.1.0.1 7
FSFR-XS Series — Fairchild Power Switch (FPS™) for Hal f-Bri dge Resonant Converter
Typical Performance Characteristics
These characteristic graphs are normalized at TA=25ºC.
0.9
0.95
1
1.05
1.1
-50 -25 0 25 50 75 100
Temp (
O
C)
Normalized at 25
O
C
Temp (
O
C)
0.9
0.95
1
1.05
1.1
-50 -25 0 25 50 75 100
Normalized at 25
O
C
Figure 4. Low-Side MOSFET Duty Cycle
vs. Temperature Figure 5. Switching Frequency vs. Temperature
0.9
0.95
1
1.05
1.1
-50 -25 0 25 50 75 100
Temp (
O
C)
Normalized at 25
O
C
0.9
0.95
1
1.05
1.1
-50 -25 0 25 50 75 100
Temp (
O
C)
Normalized at 25
O
C
Figure 6. High-Side VCC (H
V
CC) Start vs. Temperatu
r
eFigure 7. High-Side VCC (H
V
CC) Stop vs. Temperature
0.9
0.95
1
1.05
1.1
-50 -25 0 25 50 75 100
Temp (
O
C)
Normalized at 25
O
C
0.9
0.95
1
1.05
1.1
-50 -25 0 25 50 75 100
Temp (
O
C)
Normalized at 25
O
C
Figure 8. Low-Side VCC (L
V
CC) Start vs. Temperature Figure 9. Low-Side VCC (L
V
CC) Stop vs. Temperature
© 2010 Fairchild Semiconductor Corporation www.fairchildsemi.com
FSFR-XS Series • Rev.1.0.1 8
FSFR-XS Series — Fairchild Power Switch (FPS™) for Hal f-Bri dge Resonant Converter
Typical Performance Characteristics (Continued)
These characteristic graphs are normalized at TA=25ºC.
0.9
0.95
1
1.05
1.1
-50 -25 0 25 50 75 100
Temp (
O
C)
Normalized at 25
O
C
0.9
0.95
1
1.05
1.1
-50 -25 0 25 50 75 100
Temp (
O
C)
Normal ized at 25
O
C
Figure 10. LVCC OVP Voltage vs. Temperature Figure 11. RT
V
oltage vs. Temperature
0.9
0.95
1
1.05
1.1
-50-25 0 255075100
Normalized at 25℃
Temp(℃)
0.9
0.95
1
1.05
1.1
-50-25 0 255075100
Normalized at 25℃
Temp(℃)
Figure 12.
V
CssL vs. Temperature Figure 13.
V
CssH vs. Temperature
0.9
0.95
1
1.05
1.1
-50 -25 0 25 50 75 100
Temp (
O
C)
Normalized at 25
O
C
Figure 14. OCP Voltage vs. Temperature
© 2010 Fairchild Semiconductor Corporation www.fairchildsemi.com
FSFR-XS Series • Rev.1.0.1 9
FSFR-XS Series — Fairchild Power Switch (FPS™) for Hal f-Bri dge Resonant Converter
Functional Description
1. Basic Operation. FSFR-XS series is designed to
drive high-side and low-side MOSFETs complementarily
with 50% duty cycle. A fixed dead time of 350ns is
introduced between consecutive transitions, as shown in
Figure 15.
Figure 15. MOSFETs Gate Drive Signal
2. Internal Oscillator: FSFR-XS series employs a
current-controlled oscillator, as shown in Figure 16.
Internally, the voltage of RT pin is regulated at 2V and the
charging / discharging current for the oscillator capacitor,
CT, is obtained by copying the current flowing out of the
RT pin (ICTC) using a current mirror. Therefore, the
switching frequency increases as ICTC increases.
Figure 16. Current-Controlled Oscillator
3. Frequency Setting: Figure 17 shows the typical
voltage gain curve of a resonant converter, where the
gain is inversely proportional to the switching frequency
in the ZVS region. The output voltage can be regulated
by modulating the switching frequency. Figure 18 shows
the typical circuit configuration for the RT pin, where the
opto-coupler transistor is connected to the RT pin to
modulate the switching frequency.
The minimum switching frequency is determined as:
min
min
5.2 100( )
k
f
kHz
R
Ω
=× (1)
Assuming the saturation voltage of opto-coupler
transistor is 0.2V, the maximum switching frequency is
determined as:
max
min max
5.2 4.68
( ) 100( )
kk
fkHz
RR
ΩΩ
=+ × (2)
Figure 17. Resonant Converter Typical Gain Curve
LVCC
RT
AR
CS
SG PG
Rmin Rss
Css
VDL
Rmax
Figure 18. Frequency Control Circuit
To prevent excessive inrush current and overshoot of
output voltage during startup, increase the voltage gain
of the resonant converter progressively. Since the
voltage gain of the resonant converter is inversely
proportional to the switching frequency, the soft-start is
implemented by sweeping down the switching frequency
from an initial high frequency (fISS) until the output
voltage is established. The soft-start circuit is made by
connecting R-C series network on the RT pin, as shown
in Figure 18. FSFR-XS series also has a 3ms internal
soft-start to reduce the current overshoot during the initial
cycles, which adds 40kHz to the initial frequency of the
external soft-start circuit, as shown in Figure 19. The
initial frequency of the soft-start is given as:
min
5.2 5.2
()10040()
ISS
SS
kk
fkHz
RR
Ω
Ω
=+×+ (3)
© 2010 Fairchild Semiconductor Corporation www.fairchildsemi.com
FSFR-XS Series • Rev.1.0.1 10
FSFR-XS Series — Fairchild Power Switch (FPS™) for Hal f-Bri dge Resonant Converter
It is typical to set the initial frequency of soft-start two to
three times the resonant frequency (fO) of the resonant
network. The soft-start time is three to four times the RC
time constant. The RC time constant is:
SSSS CR •=τ (4)
Figure 19. Frequency Sweeping of Soft-Start
4. Self Auto-Restart: The FSFR-XS series can restart
automatically even though any built-in protections are
triggered with external supply voltage. As can be seen in
Figure 20 and Figure 21, once any protections are
triggered, the M1 switch turns on and the V-I converter is
disabled. CSS starts to discharge until VCss across CSS
drops to VCssL. Then, all protections are reset, M1 turns
off, and the V-I converter resumes at the same time. The
FSFR-XS starts switching again with soft-start. If the
protections occur while VCss is under VCssL and VCssH
level, the switching is terminated immediately, VCss
continues to increase until reaching VCssH, then CSS is
discharged by M1.
Figure 20. Internal Block of AR Pin
After protections trigger, FSFR-XS is disabled during the
stop-time, tstop, where VCss decreases and reaches to
VCssL. The stop-time of FSFR-XS can be estimated as:
(){}
Ω+•= kRRCt MINSSSSSTOP 5|| (5)
The soft-start time, ts/s can be set as Equation (4).
LV
CC
I
Cr
V
AR
t
stop
t
S/S
V
CssH
(a) (a)(a)(b) (b)
(a ) P rotection s are trigge red, (b)F SF R-U S restarts
V
CssL
(b)
Figure 21. Self Auto-Restart Operation
5. Protection Circuits: The FSFR-XS series has several
self-protective functions, such as Over-Current Protection
(OCP), Abnormal Over-Current Protection (AOCP), Over-
Voltage Protection (OVP), and Thermal Shutdown (TSD).
These protections are auto-restart mode protections, as
shown in Figure 22.
Once a fault condition is detected, switching is terminated
and the MOSFETs remain off. When LVCC falls to the LVCC
stop voltage of 10V or AR signal is HIGH, the protection is
reset. The FSFR-XS resumes normal operation when
LVCC reaches the start voltage of 12.5V.
Figure 22. Protection Blocks
5.1 Over-Current Protection (OCP): When the
sensing pin voltage drops below -0.58V, OCP is
triggered and the MOSFETs remain off. This protection
has a shutdown time delay of 1.5µs to prevent
premature shutdown during startup.
5.2 Abnormal Over-Current Protection (AOCP): If
the secondary rectifier diodes are shorted, large
current with extremely high di/dt can flow through the
MOSFET before OCP is triggered. AOCP is triggered
without shutdown delay if the sensing pin voltage
drops below -0.9V.
© 2010 Fairchild Semiconductor Corporation www.fairchildsemi.com
FSFR-XS Series • Rev.1.0.1 11
FSFR-XS Series — Fairchild Power Switch (FPS™) for Hal f-Bri dge Resonant Converter
5.3 Over-Voltage Protection (OVP): When the LVCC
reaches 23V, OVP is triggered. This protection is used
when auxiliary winding of the transformer to supply VCC
to the FPS™ is utilized.
5.4 Thermal Shutdown (TSD): The MOSFETs and
the control IC in one package makes it easier for the
control IC to detect the abnormal over-temperature of
the MOSFETs. If the temperature exceeds
approximately 130°C, thermal shutdown triggers.
6. Current Sensing Using a Resistor: FSFR-XS series
senses drain current as a negative voltage, as shown in
Figure 23 and Figure 24. Half-wave sensing allows low
power dissipation in the sensing resistor, while full-wave
sensing has less switching noise in the sensing signal.
Control
IC
CS
SG PG
Ns
Np Ns
Rsense
Ids
Cr
Ids
VCS
VCS
Figure 23. Half-Wave Sensing
Control
IC
CS
SG PG
Rsense
Ids
VCS
Ids
VCS
Ns
Np Ns
Cr
Figure 24. Full-Wave Sensing
7. PCB Layout Guidelines: Duty imbalance problems
may occur due to the radiated noise from the main
transformer, the inequality of the secondary side leakage
inductances of main transformer, and so on. This is one
of the reasons that the control components in the vicinity
of RT pin are enclosed by the primary current flow pattern
on PCB layout. The direction of the magnetic field on the
components caused by the primary current flow is
changed when the high- and low-side MOSFET turn on
by turns. The magnetic fields with opposite directions
induce a current through, into, or out of the RT pin, which
makes the turn-on duration of each MOSFET different. It
is strongly recommended to separate the control
components in the vicinity of RT pin from the primary
current flow pattern on PCB layout. Figure 25 shows an
example for the duty-balanced case.
Figure 25. Example for Duty Balancing
© 2010 Fairchild Semiconductor Corporation www.fairchildsemi.com
FSFR-XS Series • Rev.1.0.1 12
FSFR-XS Series — Fairchild Power Switch (FPS™) for Hal f-Bri dge Resonant Converter
Physical Dimensions
Figure 26. 9-Lead Single Inline Package (SIP)
Package drawings are provided as a service to customers consideri ng Fairchild components. Drawings may change in any manner
without notic e. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representativ e to verify or
obtain the most recent revisi on. Package specific ati ons do not ex pand the terms of Fairchild’s worl dwide terms and condi tions,
specifically the warranty therein, which covers Fairchild products.
Always visit Fairchi l d Semiconductor ’s online packaging area for the most recent package drawings:
http://www.fairchildsemi.com/packaging/.
© 2010 Fairchild Semiconductor Corporation www.fairchildsemi.com
FSFR-XS Series • Rev.1.0.1 13
FSFR-XS Series — Fairchild Power Switch (FPS™) for Hal f-Bri dge Resonant Converter
Physical Dimensions
Figure 27. 9-Lead Single Inline Package (SIP) L-Forming
Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner
without notic e. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representativ e to verify or
obtain the most recent revisi on. Package specific ati ons do not ex pand the terms of Fairchild’s worl dwide terms and condi tions,
specifically the warranty therein, which covers Fairchild products.
Always visit Fairchi l d Semiconductor ’s online packaging area for the most recent package drawings:
http://www.fairchildsemi.com/packaging/.
© 2010 Fairchild Semiconductor Corporation www.fairchildsemi.com
FSFR-XS Series • Rev.1.0.1 14
FSFR-XS Series — Fairchild Power Switch (FPS™) for Hal f-Bri dge Resonant Converter
