FSFR2100US - Fairchild Semiconductor Corporation

May 2010

FSFR-US Series • Rev.1.0.2

FSFR-US Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter

FSFR-US Series — Fairchild Pow er 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™s with Fast-Recovery Type

Body Diode

 Fixed Dead Time (350ns) Optimized for MOSFETs

 Up to 300kHz Operating Frequency

 Auto-Restart Operation for All Protections with An

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-US series are a 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-

US series simplifies designs and improves productivity,

while improving performance. The FSFR-US 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 a 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 the reverse

recovery. Using the zero-voltage-switching (ZVS)

technique dramatically reduces the switching losses and

efficiency is significantly improved. The ZVS also

reduces the switching noise noticeably, which allows a

small-sized Electromagnetic Interference (EMI) filter.

The FSFR-US series can be applied to various 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)

FSFR2100US

9-SIP

-40 to +130°C

0.51Ω 180W 400W

FSFR1800US 0.95Ω 120W 260W

FSFR1700US 1.25Ω 100W 200W

FSFR2100USL

9-SIP

L-Forming

0.51Ω 180W 400W

FSFR1800USL 0.95Ω 120W 260W

FSFR1700USL 1.25Ω 100W 200W

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.

FSFR-US Series • Rev.1.0.2 2

FSFR-US Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter

Application Circuit Diagram

Figure 1. Typical Application Circuit (LLC Resonant Half-Bridge Converter)

Block Diagram

Figure 2. Internal Block Diagram

FSFR-US Series • Rev.1.0.2 3

FSFR-US Series — Fairchild Power Switch (FPS™) for Half-Bridge 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 0.2, 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.

FSFR-US Series • Rev.1.0.2 4

FSFR-US Series — Fairchild Power Switch (FPS™) for Half-Bridge 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)

FSFR2100US/L 12.0

W FSFR1800US/L 11.7

FSFR1700US/L 11.6

TJ Maximum Junction Temperature(4) +150

°C

Recommended Operating Junction Temperature(4) -40 +130

TSTG Storage Temperature Range -55 +150 °C

Notes:

3. Per MOSFET when both MOSFETs are conducting.

4. The maximum value of the recommended operating junction temperature is limited by thermal shutdown.

FSFR-US Series • Rev.1.0.2 5

FSFR-US Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter

Absolute Maximum Ratings (Continued)

Symbol Parameter Min. Max. Unit

MOSFET Section

VDGR Drain Gate Voltage (RGS=1MΩ) 500 V

VGS Gate Source (GND) Voltage ±30 V

IDM Drain Current Pulsed(5)

FSFR2100US/L 32

A FSFR1800US/L 23

FSFR1700US/L 20

ID Continuous Drain Current

FSFR2100US/L TC=25°C 10.5

TC=100°C 6.5

FSFR1800US/L TC=25°C 7.0

TC=100°C 4.5

FSFR1700US/L TC=25°C 6.0

TC=100°C 3.9

Package Section

Torque Recommended Screw Torque 5~7 kgf·cm

Notes:

5. Pulse width is limited by maximum junction temperature.

Thermal Impedance

TA=25°C unless otherwise specified.

Symbol Parameter Value Unit

θJC Junction-to-Case Center Thermal Impedance

(Both MOSFETs Conducting)

FSFR2100US/L 10.44

ºC/W

FSFR1800US/L 10.68

FSFR1700US/L 10.79

FSFR-US Series • Rev.1.0.2 6

FSFR-US Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter

Electrical Characteristics

TA=25°C unless otherwise specified.

Symbol Parameter Test Conditions Specifications Unit

Min. Typ. Max.

MOSFET Section

BVDSS Drain-to-Source Breakdown Voltage ID=200μA, TA=25°C 500

ID=200μA, TA=125°C 540

RDS(ON) On-State Resistance

FSFR2100US/L VGS=10V, ID=6.0A 0.41 0.51

FSFR1800US/L VGS=10V, ID=3.0A 0.77 0.95

FSFR1700US/L VGS=10V, ID=2.0A 1.00 1.25

trr Body Diode Reverse

Recovery Time(6)

FSFR2100US/L VGS=0V, IDiode=12.0A,

dIDiode/dt=100A/μs 120

FSFR1800US/L VGS=0V, IDiode=7.0A,

dIDiode/dt=100A/μs 160

FSFR1700US/L VGS=0V, IDiode=6.0A,

dIDiode/dt=100A/μs 160

Supply Section

ILK Offset Supply Leakage Current H-VCC=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

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) 8.90 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

FSFR-US Series • Rev.1.0.2 7

FSFR-US Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter

Electrical Characteristics (Continued)

TA=25°C unless otherwise specified.

Symbol Parameter Test Conditions

Specifications Unit

Min Typ Max

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 L-VCC > 21V 21 23 25 V

VAOCP AOCP Threshold Voltage ΔV/Δt=-0.1V/µs -1.0 -0.9 -0.8 V

tBAO AOCP Blanking Time(6) VCS < VAOCP;

ΔV/Δt=-0.1V/µs 50 ns

VOCP OCP Threshold Voltage V/Δt=-1V/µs -0.64 -0.58 -0.52 V

tBO OCP Blanking Time(6) VCS < VOCP;

ΔV/Δt=-1V/µs 1.0 1.5 2.0 μs

tDA Delay Time (Low Side) Detecting from VAOCP

to Switch Off(6) ΔV/Δt=-1V/µs 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.

FSFR-US Series • Rev.1.0.2 8

FSFR-US Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter

Typical Performa nce Characteristics

These characteristic graphs are normalized at TA=25ºC.

0.9

0.95

1.05

1.1

-50 -25 0 25 50 75 100

Temp (

Normalized at 25

Temp (

0.9

0.95

1.05

1.1

-50 -25 0 25 50 75 100

Normalized at 25

Figure 4. Low-Side MOSFET Duty Cycle

vs. Temperature Figure 5. Switching Frequency vs. Temperature

0.9

0.95

1.05

1.1

-50 -25 0 25 50 75 100

Temp (

Normalized at 25

0.9

0.95

1.05

1.1

-50 -25 0 25 50 75 100

Temp (

Normalized at 25

Figure 6. High-Side VCC (H

CC) Start vs. Temperature Figure 7. High-Side VCC (H

CC) Stop vs. Temperature

0.9

0.95

1.05

1.1

-50 -25 0 25 50 75 100

Temp (

Normalized at 25

0.9

0.95

1.05

1.1

-50 -25 0 25 50 75 100

Temp (

Normalized at 25

Figure 8. Low-Side VCC (L

CC) Start vs. Temperature Figure 9. Low-Side VCC (L

CC) Stop vs. Temperature

FSFR-US Series • Rev.1.0.2 9

FSFR-US Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter

Typical Performa nce Characteristics (Continued)

These characteristic graphs are normalized at TA=25ºC.

0.9

0.95

1.05

1.1

-50 -25 0 25 50 75 100

Temp (

Normalized at 25

0.9

0.95

1.05

1.1

-50 -25 0 25 50 75 100

Temp (

Normalized at 25

Figure 10. LVCC OVP Voltage vs. Temperature Figure 11. RT

oltage vs. Temperature

0.90

0.95

1.00

1.05

1.10

-50-25 0 255075100

Normalized

at 25Ԩ

Temp(Ԩ)

0.90

0.95

1.00

1.05

1.10

-50-25 0 255075100

Normalized

at 25Ԩ

Temp(Ԩ)

Figure 12.

CssL vs. Temperature Figure 13.

CssH vs. Temperature

0.9

0.95

1.05

1.1

-50 -25 0 25 50 75 100

Temp (

Normalized at 25

Figure 14. OCP Voltage vs. Temperature

FSFR-US Series • Rev.1.0.2 10

FSFR-US Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter

Functional Description

1. Basic Operation: FSFR-US 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-US 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

5.2 100( )

kHz

=× (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( )

fkHz

ΩΩ

=+ × (2)

Figure 17. Resonant Converter Typical Gain Curve

FSFR-US

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-US series also has an internal soft-

start for 3ms 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

fkHz

=+×+ (3)

FSFR-US Series • Rev.1.0.2 11

FSFR-US Series — Fairchild Power Switch (FPS™) for Half-Bridge 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 of the RC time

constant. The RC time constant is as follows:

SSSS CR •=τ (4)

Figure 19. Frequency Sw eeping of Soft-Start

4. Self Auto-Restart: The FSFR-US 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, M1 switch turns on and V-I converter is

disabled. CSS starts to be discharged until VCss across

CSS drops to VCssL. Then, all protections are reset, M1

turns off, and V-I converter resumes at the same time.

The FSFR-US 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-US is disabled during the

stop-time, tstop, where VCss decreases and reaches to

VCssL. The stop-time of FSFR-US can be estimated as:

(){}

Ω=•= k5||RRCt MINSSSSSTOP (5)

For the soft-start time, ts/s it can be set as Equation (4).

stop

S/S

CssH

(a) (a)(a)(b) (b)

(a) Pr ote ctions are trigge red, (b)F SFR-U S restarts

CssL

(b)

Figure 21. Self Auto-Restart Operation

5. Protection Circuits: The FSFR-US 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-US 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 when the sensing pin voltage

drops below -0.9V.

FSFR-US Series • Rev.1.0.2 12

FSFR-US Series — Fairchild Power Switch (FPS™) for Half-Bridge 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 FPS is utilized.

5.4 Thermal Shutdown (TSD): The MOSFETs and

the control IC in one package makes it easy for the

control IC to detect the abnormal over-temperature of

the MOSFETs. If the temperature exceeds

approximately 130°C, the thermal shutdown triggers.

6. Current Sensing Using Resistor: FSFR-US 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

SG PG

Np Ns

Rsense

Ids

VCS

Figure 23. Half-Wave Sensing

Control

SG PG

Rsense

Ids

VCS

Ids

VCS

Np Ns

Figure 24. Full-Wave Sensing

7. PCB Layout Guidelines: Duty unbalance problems

may occur due to the radiated noise from main

transformer, the inequality of the secondary side leakage

inductances of main transformer, and so on. Among

them, it is one of the dominant reasons that the control

components in the vicinity of RT pin are enclosed by the

primary current flows 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

FSFR-US Series • Rev.1.0.2 13

FSFR-US Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter

Physical Dimensions

SIPMODAA09revA

NOTES:UNLESS OTHERWISESPECIFIED

A) THIS PACKAGE DOES NOT COMPLY

TOANY CURRENT PACKAGING STANDARD.

B) ALL DIMENSIONS ARE IN MILLIMETERS.

C) DIMENSIONS ARE EXCLUSIVE OF BURRS,

MOLD FLASH, AND TIE BAR EXTRUSIONS.

26.20

25.80

23.10

22.90

3.40

3.00

0.60

0.40

3.48

2.88

3.40

3.00

1.27

15.24

5.35

5.15

(5.08)

MAX1.30

MAX 0.80

(1.70) (1.20)

(R0.50)

R0.55

14.50

13.50

(7.00)

(0.50) 18.50

17.50

1.30

1.10

10.70

10.30

8.00

7.00

(0.70)

(11.00)

(R0.50)

0.70

0.50

Figure 26. 9-SIP Package

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/.

FSFR-US Series • Rev.1.0.2 14

FSFR-US Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter

Physical Dimensions

Figure 27. 9-SIP L-Forming Package

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/.

FSFR-US Series • Rev.1.0.2 15

FSFR-US Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter