FAN6208 Secondary-Side Synchronous Rectifier Controller for LLC Topology Features Description Specialized SR Controller for LLC or LC Resonant Converters Secondary-Side Timing Detection with Timing Estimator Gate-Shrink Function to Prevent Shoot-Through During Load and Line Transient Green-Mode Function for Higher Efficiency at LightLoad Condition Programmable Dead Time between Primary-Side Gate Drive Signal and SR Drive Signal Advanced Output-Short / Overload Protection Based on the Feedback Information FAN6208 is a synchronous rectification (SR) controller for isolated LLC or LC resonant converters that can drive two individual SR MOSFETs emulating the behavior of rectifier diodes. FAN6208 measures the SR conduction time of each switching cycle by monitoring the drain-to-source voltage of each SR and determines the optimal timing of the SR gate drive. FAN6208 uses the change of opto-coupler diode current to adaptively shrink the duration of SR gate drive signals during load transients to prevent shoot-through. To improve lightload efficiency, Green-Mode operation is employed, which disables the SR drive signals, minimizing gate drive power consumption at light-load condition. Internal Over-Temperature Protection (OTP) Optimal timing circuits and protection functions are integrated in an 8-pin SOP package, which allows highefficiency power supply design with fewer components. VDD Pin Over-Voltage Protection (OVP) Applications LCD TV PC Power Open-Frame SMPS Ordering Information Part Number FAN6208MY Operating Temperature Range Package Packing Method -40°C to +105°C 8-Pin Small Outline Package (SOP) Tape & Reel © 2010 Fairchild Semiconductor Corporation FAN6208 • Rev. 1.0.1 www.fairchildsemi.com FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology November 2010 Figure 1. Typical Application Block Diagram FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology Application Diagram Figure 2. Block Diagram © 2010 Fairchild Semiconductor Corporation FAN6208 • Rev. 1.0.1 www.fairchildsemi.com 2 FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology Marking Information F- Fairchild Logo Z- Plant Code X- Year Code Y- Week Code TT: Die Run Code T - Package Type (M = SOP) P - Y: Green Package M - Manufacture Flow Code 6208 6208 TPM Figure 3. Top Mark Pin Configuration Figure 4. Pin Assignments Pin Definitions Pin # Name Description 1 DETL1 Low Detect provides low-voltage detection of VDS of SR MOSFET1. 2 DETL2 Low Detect provides low-voltage detection of VDS of SR MOSFET2. 3 RP Dead Time Programming Resistor programs H/L frequency version and dead time. 4 FD Feedback Detection is used for short-circuit protection and gate shrink. 5 VDD 6 GATE2 7 GND 8 GATE1 Power Supply Driver Output. The totem-pole output driver for driving the SR MOSFET2. Ground Driver Output. The totem-pole output driver for driving the SR MOSFET1. © 2010 Fairchild Semiconductor Corporation FAN6208 • Rev. 1.0.1 www.fairchildsemi.com 3 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. Symbol Parameter Min. Max. Unit VDD Supply Voltage 30 V VFD Voltage on FD Pin 30 V VLV Voltage on DETL1, DETL2, RP Pins -0.3 7.0 V PD Power Dissipation 350Mw at TA=90°C 1000mW at TA=25°C ΘJA Junction–to-Ambient Thermal Resistance 130 °C/W ΨJT Junction-to-Top Thermal Characteristics 45 °C/W TJ TSTG TL ESD Operating Junction Temperature -40 +125 °C Storage Temperature Range -55 +150 °C +260 °C Lead Temperature (Wave Soldering or IR, 10 Seconds) Human Body Model, JESD22-A114 6 Charged Device Model, JESD22-C101 2 kV Recommended Operating Conditions The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended operating conditions are specified to ensure optimal performance to the datasheet specifications. Fairchild does not recommend exceeding them or designing to Absolute Maximum Ratings. Symbol TA Parameter Operating Ambient Temperature © 2010 Fairchild Semiconductor Corporation FAN6208 • Rev. 1.0.1 Min. Max. Unit -40 +105 °C FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology Absolute Maximum Ratings www.fairchildsemi.com 4 VDD=20V, TA=25°C, unless otherwise specified. All voltages are with respect to GND unless otherwise noted. Symbol Parameter Conditions Min. Typ. Max. Units 28 V VDD Section VDD DC Supply Voltage VTH-OFF IDD-OP1 Operating Current VDD=12V, DETL=50KHz, CL=6nF, RRP=24K 7.0 8.5 10.0 mA IDD-OP2 Operating Current VDD=12V, DETL=100KHz 2.4 3.2 4.0 mA IDD-ST Startup Current VDD=8V 180 300 500 μA 9.3 9.7 10.1 V Off Threshold Voltage 8.3 8.8 9.3 V VCC Over-Voltage Protection 26 27 28 V VDD-OVP-HYS1 VDD-OVP-HYS2 VCC Over-Voltage Protection Hysteresis 1.3 1.8 2.3 V tOVP1,tOVP2 VCC Over-VoltageProtection Debounce 30 60 100 μs Threshold Voltage for LOW VDD=12V, DETL=50KHz, Detection of DETL CL=6nF, RRP=24KΩ 1.7 2.0 2.3 V Delay from DETL LOW to SR Gate Turn-On tDB+ tPD+ tR 300 350 400 ns VDD=12V, DETL Pin Floating 4.5 DETL Source Current VDETL1=0V 40 50 60 μA DETL LOW Time Threshold for Green Mode at Low-Frequency Operation VRP < 1.5V 3.50 3.75 4.00 μs DETL LOW Time tDET(L)_Green_HF1 Threshold for Green Mode tDET(L)_Green_HF2 at High-Frequency Operation VRP > 1.5V 1.75 1.90 2.05 μs VTH-ON1 VTH-ON2 On Threshold Voltage VTH-OFF1 VTH-OFF2 VDD-OVP1 VDD-OVP2 DETL Section VDETL1 VDETL2 tSR-ON-DETL1 tSR-ON-DETL2 VDETL-FLOATING1 DETL Floating Voltage VDETL-FLOATING2 IDETL-SOURCE1 IDETL-SOURCE2 tDETL_Green_LF1 tDETL_Green_LF2 V FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology Electrical Characteristics Thermal Shutdown TSHUTDOWN Shutdown Temperature Temperature Rising, VDD=15V Hysteresis TSTARTUP Startup Temperature 140 20 Before Startup °C 120 Continued on the following page… © 2010 Fairchild Semiconductor Corporation FAN6208 • Rev. 1.0.1 www.fairchildsemi.com 5 VDD=20V, TA=25°C, unless otherwise specified. All voltages are with respect to GND unless otherwise noted. Symbol Parameter Conditions Min. Typ. Max. Units 10 12 14 V 0.5 V Gate Section Gate Output Voltage Maximum (Clamping) VDD=20V VOL1 VOL2 Gate Output Voltage LOW VDD=12V; IO=100mA VOH1VOH2 Gate Output Voltage HIGH VDD=12V; IO=100mA 9 tR1 tR2 Rising Time VDD=12V; CL=6nF; VGATE=2V to 9V 30 70 120 ns tF1 tF2 Falling Time VDD=12V; CL=6nF; VGATE=9V to 2V 30 50 70 ns tPD_HIGH_DETL1 tPD_HIGH_DETL2 Propagation Delay to Gate Output HIGH (DETL Trigger) tR: 0V~2V, VDD=12V (DET Floating) 120 ns tPD_LOW_ DETL1 tPD_LOW_ DETL2 Propagation Delay to Gate Output LOW (DETL Trigger) tF: 100%~90%, VDD=12V (DET Floating) 120 ns Maximum On-Time Trim Maximum On-Time 9.0 10.5 12.0 μs tINHIBIT_LF1 tINHIBIT_LF2 Gate Inhibit Time (from Turn-Off to Next Turn-On) VRP < 1.5V 1.8 2.1 2.5 μs tINHIBIT_HF1 tINHIBIT_HF2 Gate Inhibit Time (from Turn-Off to Next Turn-On) VRP > 1.5V 1.25 1.45 1.70 μs tBLANKING1 tBLANKING2 Blanking Time for SR TurnOff Triggered by DETL High (Minimum On-Time) VZ1 VZ2 tON_MAX1 tON_MAX2 KR Gate ON-Time Increase Rate Between Two Consecutive Cycles tON(n) / tON(n-1) % V 300 ns 140 % Timing Estimator Section tDW Detection Window for Insufficient Dead Time (from Gate Turn-Off to DETL HIGH) tSHRINK-DT Gate Shrink Time by Insufficienct Dead Time tDEAD tDB tSHRINK-RNG tGreen_DH 80 125 150 ns RRP=20KΩ, tDETL=5μs 1.00 1.25 1.50 μs Dead Time by Timing Estimator (70kHz ~ 140kHz, VRP < 1.5V) tDETL=4μs, RRP=20KΩ 210 300 390 tDETL=6μs, RRP=20KΩ 570 720 870 Dead Time by Timing Estimator (160kHz ~ 240kHz, VRP > 1.5V) tDETL=2.5μs, RRP=43KΩ 220 320 420 tDETL=3.8μs, RRP=43KΩ 560 670 780 ns DETL HIGH-to-LOW Debounce Time for Gate Turn-on Trigger 150 ns Gate Shrink by DETL Ringing around Zero 1.2 μs DETL Pull-HIGH Time Threshold for Green Mode 18 24 30 FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology Electrical Characteristics μs Continued on the following page… © 2010 Fairchild Semiconductor Corporation FAN6208 • Rev. 1.0.1 www.fairchildsemi.com 6 VDD=20V, TA=25°C, unless otherwise specified. All voltages are with respect to GND unless otherwise noted. Symbol Parameter Conditions Min. Typ. Max. Units Feedback Detection (FD) Section ∆V1% ∆V2% Feedback Increase Threshold for Gate Shrink tSHRINK-FD Gate Shrink by Feedback Detection tD-SHRINK-FD Gate-Shrink Duration by Feedback Detection 60 90 120 μs VDD-VFD.SCP Short-Circuit Protection (SCP) Threshold by Feedback Detection 200 270 340 mV Debounce Time for ShortCircuit Protection (SCP) 12 16 20 μs RP Source Current 38.5 41.5 44.5 μA VRPO RP Open Protect 3.40 3.65 3.90 V VRPS RP Short Protect 0.25 0.30 0.35 V tRPOS RP Open/Short Debounce 1.6 2.0 2.4 μs VRPHL H/L Frequency Threshold 1.40 1.46 1.52 V tDB-SCP [(VDD-VFD)n+1/(VDD-VFD)n] 120 % 1.4 μs RP Section IRP Figure 5. tDEAD vs. tDETL RP Curve for LF Mode © 2010 Fairchild Semiconductor Corporation FAN6208 • Rev. 1.0.1 FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology Electrical Characteristics Figure 6. tDEAD vs. tDETL RP Curve for HF Mode www.fairchildsemi.com 7 Operation Principle FAN6208 is a secondary-side synchronous rectifier controller for LLC or LC resonant converters that drive two synchronous rectifier MOSFETs. Figure 7 is the simplified circuit diagram of an LLC converter. The FAN6208 determines SR MOSFET turn-on/off timing by detecting the drain-to-source voltage of each SR MOSFET. The key waveforms for LLC resonant converter for below resonance and above resonance are shown in Figure 8 and Figure 9, respectively. Secondary-Side Synchronous Rectifiers VIN SR1 IP VO Lr Lm DETL1 GATE1 DETL2 GND Cr RP GATE2 FD VDD FAN6208 LLC Resonant Converter SR2 Figure 7. Simplified Schematic of LLC Converter Figure 9. Key Waveforms of LLC Resonant Converter for Above Resonance Operation Timing Estimator Figure 10 shows the timing diagram for FAN6208. Once the body diode of SR begins conducting, the drain-tosource voltage drops to zero, which causes DETL pin voltage to drop to zero. FAN6208 turns on the MOSFET after tON-ON-DETL (about 350ns), when voltage on DETL drops below 2V. As depicted in Figure 11, the turn-on delay (after tSR-ON-DETL) is the sum of debounce time (150ns) and propagation delay (200ns). FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology Function Description FAN6208 measures the SR conduction duration (tDETL), during which DETL stays lower than 2V, and uses this information to determine the turn-off instant of SR gates of the next switching cycle. The turn-off timing is obtained by subtracting a dead time (tDEAD) from the measured SR conduction duration of the previous switching cycle. The dead time can be programmed using a resistor on the RP pin and the relationship between the dead time and SR conduction duration (tDETL) for different resistor values on RP pin is given in Figure 5. Figure 8. Key Waveforms of LLC Resonant Converter for Below Resonance Operation © 2010 Fairchild Semiconductor Corporation FAN6208 • Rev. 1.0.1 www.fairchildsemi.com 8 (a) When insufficient dead time is detected in the previous switching cycle. When the DETL goes HIGH within 125ns of detection window after SR gate is turned off, the SR gate drive signal in the next switching cycle is reduced by tSHRINK-DT (about 1.25µs) to increase the dead time, as shown in Figure 12. Figure 10. SR Gate Timing Diagram Figure 12. Gate Shrink by Minimum Dead Time Detection Window (b) When the feedback information changes fast. FAN6208 monitors the current through the optocoupler diode by measuring the voltage across the resistor in series with the opto-coupler diode, as depicted in Figure 13. If the feedback current through the opto-coupler diode increases by more than 20% of the feedback current of the previous switching cycle, the SR gate signal is shrunk by tSHRINK-FD (about 1.4µs) for tD-SHRINK-FD (about 90µs), as shown in Figure 14. FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology side MOSFETs takes place before the turn-off command of SR is given. To prevent the shoot-through, FAN6208 has gate-shrink functions. Gate shrink occurs under three conditions: Figure 11. DETL Debounce (Blanking) Time Gate-Shrink Functions In normal operation, the turn-off instant is determined by subtracting a dead time (tDEAD) from the measured SR conduction duration of the previous switching cycle, as shown in Figure 10. This allows proper driving timing for SR MOSFETS when the converter is in steady state and the switching frequency does not change much. However, this control method may cause shoot-through of SR MOSFETs when the switching frequency increases fast and switching transition of the primary© 2010 Fairchild Semiconductor Corporation FAN6208 • Rev. 1.0.1 Figure 13. Typical Application Circuit www.fairchildsemi.com 9 RP Pin Operation (c) When the DETL voltage has ringing around zero. As depicted in Figure 8, the drain voltage of SR has ringing around zero at light-load condition after the switching transition of the primary-side switches. When DETL voltage rises above 2V within 350ns after DETL voltage drops to zero and stays above 2V longer than 150ns, the gate is shrunk by 1.2µs (tSHRINK-RNG), as shown in Figure 15. To handle abnormal conditions for IC pins, the RP pin also provides open/short protection. When VRP is less than VRPS (0.3V) or VRP is higher than VRPO (3.65V), the protection is triggered. Figure 17 shows the RP pin short protection timing sequence. If VRP < VRPS (0.3V) for longer than tRPOS (2µs), FAN6208 is disabled. Figure 18 shows the RP pin open protection timing sequence. If VRP > VRPO (3.65V) for longer than tRPOS (2µs), FAN6208 is disabled. Figure 15. Gate Shrink by DETL Voltage Ringing Around Zero Figure 17. RP Pin Short Protection FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology Figure 16. Figure 14. Gate Shrink by Feedback Detection RP Pin Function The RP pin programs the level of green mode and tDEAD. Figure 16 shows how the mode is selected by the voltage on the RP pin (open protection, short protection, and HF/LF mode). When RRP is less than 36KΩ, FAN6208 operates in low-frequency mode. Green mode is enabled when tDETL is smaller than 3.75µs. When RRP is larger than 36KΩ, high-frequency mode is selected and green mode is enabled for tDETL < 1.90µs. tDEAD can be also adjusted by a resistor on the RP pin. Figure 5 shows the relationship between tDEAD and tDETL for different RP resistors. Figure 18. RP Pin Open Protection © 2010 Fairchild Semiconductor Corporation FAN6208 • Rev. 1.0.1 www.fairchildsemi.com 10 VDD Pin Over-Voltage Protection Switching frequency increases in LLC topology at lightload condition, which increases the power consumption for the SR gate drive. Green mode reduces power loss at light load. FAN6208 has two ways to enable green mode. Green mode is triggered when DETL voltage is pulled LOW for less than 3.75µs (LF mode) or 1.90µs (HF mode) for seven switching cycles. FAN6208 resumes normal SR gate driving when DETL voltage is pulled LOW for longer than 3.75µs (LF mode) or 1.90µs (HF mode) for seven switching cycles. Over-voltage conditions are usually caused by an open feedback loop. VDD over-voltage protection prevents damage of SR MOSFET. When the voltage on the VDD pin exceeds 27V, FAN6208 disables gate output. Internal Over-Temperature Protection Internal over-temperature protection prevents the SR gate from fault triggering in high temperatures. If the temperature is over 140°C, the SR gate is disabled until the temperature drops below 120°C. When DETL voltage is pulled HIGH for longer than 24µs. This occurs when the LLC resonant converter operates in burst mode (skipping mode). Short-Circuit Protection As depicted in Figure 13, FAN6208 monitors the current through the opto-coupler diode by measuring the voltage across the resistor in series with the optocoupler diode. When the output of the power supply is short circuited, the output voltage drops and the cathode of the shunt regulator (KA431) is saturated to HIGH. No current flows through the opto coupler diode. The output short protection is triggered when the voltage between VDD and FD is smaller than 0.3V, as shown in Figure 19. FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology Green Mode Figure 19. Output Short Protection by Feedback Detection © 2010 Fairchild Semiconductor Corporation FAN6208 • Rev. 1.0.1 www.fairchildsemi.com 11 Figure 20. VTH_ON1 vs. TA Figure 21. VTH_ON2 vs. TA Figure 22. VTH_OFF1 vs. TA Figure 23. VTH_OFF2 vs. TA Figure 24. IDD_ST vs. TA Figure 25. IDD_OP1 vs. TA © 2010 Fairchild Semiconductor Corporation FAN6208 • Rev. 1.0.1 FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology Typical Performance Characteristics www.fairchildsemi.com 12 Figure 26. tSR_ON_DETL1 vs. TA Figure 27. tSR_ON_DETL2 vs. TA Figure 28. VZ1 vs. TA Figure 29. VZ2 vs. TA Figure 30. VDETL1 vs. TA Figure 31. VDETL2 vs. TA © 2010 Fairchild Semiconductor Corporation FAN6208 • Rev. 1.0.1 FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology Typical Performance Characteristics (Continued) www.fairchildsemi.com 13 Figure 32. tDW1 vs. TA Figure 33. tDW2 vs. TA Figure 34. VSHRINK_DT1 vs. TA Figure 35. VSHRINK_DT2 vs. TA Figure 36. IDETL_Source1 vs. TA Figure 37. IDETL_Source2 vs. TA © 2010 Fairchild Semiconductor Corporation FAN6208 • Rev. 1.0.1 FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology Typical Performance Characteristics (Continued) www.fairchildsemi.com 14 Figure 38. tDEAD1 (RRP=20k, 6µs) vs. TA Figure 39. tDEAD2 (RRP=20k, 6µs) vs. TA Figure 40. tDEAD1 (RRP=43k, 2.5µs) vs. TA Figure 41. tDEAD2 (RRP=43k, 2.5µs) vs. TA Figure 42. IRP vs. TA Figure 43. VRPHL vs. TA © 2010 Fairchild Semiconductor Corporation FAN6208 • Rev. 1.0.1 FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology Typical Performance Characteristics (Continued) www.fairchildsemi.com 15 Application Fairchild Devices Input Voltage Range Output TV Power FAN7621 FAN6208 350~400VDC 24V/8A Figure 44. Application Circuit © 2010 Fairchild Semiconductor Corporation FAN6208 • Rev. 1.0.1 FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology Typical Application Circuit (LLC Converter with SR) www.fairchildsemi.com 16 5.00 4.80 A 0.65 3.81 5 8 B 6.20 5.80 PIN ONE INDICATOR 1.75 4.00 3.80 1 5.60 4 1.27 (0.33) 0.25 M 1.27 C B A LAND PATTERN RECOMMENDATION 0.25 0.10 SEE DETAIL A 1.75 MAX 0.25 0.19 C 0.10 0.51 0.33 0.50 x 45° 0.25 R0.10 C OPTION A - BEVEL EDGE GAGE PLANE R0.10 OPTION B - NO BEVEL EDGE 0.36 FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology Physical Dimensions NOTES: UNLESS OTHERWISE SPECIFIED 8° 0° 0.90 0.406 A) THIS PACKAGE CONFORMS TO JEDEC MS-012, VARIATION AA, ISSUE C, B) ALL DIMENSIONS ARE IN MILLIMETERS. C) DIMENSIONS DO NOT INCLUDE MOLD FLASH OR BURRS. D) LANDPATTERN STANDARD: SOIC127P600X175-8M. E) DRAWING FILENAME: M08AREV13 SEATING PLANE (1.04) DETAIL A SCALE: 2:1 Figure 45. 8-Lead, SOIC, JEDEC MS-012, .150-Inch Narrow Body Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative to verify or obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions, specifically the warranty therein, which covers Fairchild products. Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings: http://www.fairchildsemi.com/packaging/. © 2010 Fairchild Semiconductor Corporation FAN6208 • Rev. 1.0.1 www.fairchildsemi.com 17 FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology © 2010 Fairchild Semiconductor Corporation FAN6208 • Rev. 1.0.1 www.fairchildsemi.com 18