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| Product Specification Synchronous Rectifier Controller for Flyback Converter SG6203 FEATURES Low operation current (1.7mA) One resistor for timing setting Internal automatic tracking for optimum dead time No reverse energy flow at light load Best suited for primary green-mode PWM IC Wide supply voltage range from 6V to 20V Built-in 18V Zener diode Optional current sensing: - Current shunt - RC network for better efficiency DESCRIPTION The SG6203 is designed to control and drive the synchronous rectifier for the flyback converter. The synchronous signal of the primary switch is obtained by a single diode connected between the transformer secondary winding and the SG6203. Using the SG6203, no additional transformer winding is required and the circuit complexity can be minimized. The power unit can be properly operated under discontinuous conduction mode (DCM) or continuous conduction mode (CCM). Problems such as "shoot-through" or "cross conduction" in CCM and energy-reverse from the secondary to the primary in DCM are prevented by the SG6203 design. APPLICATIONS Flyback converters, such as: Power adaptors Open-frame SMPS TYPICAL APPLICATION (c) System General Corp. Version 1.0.1 (IAO33.0010.B1) -1- www.sg.com.tw * www.fairchildsemi.com September 24, 2007 Product Specification Synchronous Rectifier Controller for Flyback Converter SG6203 PIN CONFIGURATION MARKING DIAGRAMS SG6203TP XXXXXXXXYWWV T: D=DIP, S=SOP P : Z=Lead Free + ROHS Compatible XXXXXXXX: Wafer Lot Y: Year; WW: Week V: Assembly Location VCC Output GND VZ IN+ INRT DET ORDERING INFORMATION Part Number SG6203SZ SG6203DZ Pb-Free Package 8-Pin SOP 8-Pin DIP PIN DESCRIPTIONS Pin 1 2 Name Vcc Output Function Supply voltage of gate driver and control circuits. Totem-pole output to drive the synchronous power MOSFET. When the voltage on DET pin falls below 1.4V from above 2.1V, the synchronous MSOFET is turned on. To prevent the reversed energy flow, this pin is disabled once the voltage on IN+ pin is lower than that of IN- pin or the internal one-shot timer is terminated. The power ground and signal ground. A 0.1F decoupling capacitor placed between VCC and GND is recommended. Built-in 18V Zener diode. When the flyback output voltage is higher than 18V, this pin can be used to provide a stable 18V to VCC pin. If the flyback output voltage is lower than 18V, this pin can be left open and the output voltage connected directly to VCC pin. Connecting a diode from this pin to the transformer secondary winding provides on/off information of the primary switch. Low DET level indicates the secondary rectifier is conducted, therefore the synchronous MOSFET should be turned on. DET stays high when the primary switch is conducting or secondary rectifier turns off and the synchronous MOSFET should be turned off. Current reference. Connecting a resistor from this pin to ground can program the internal current reference IRT. Three internal current sources, which are IIN+, IIN-, and IDET, are then mirrored from IRT. IRT determines the duration of the internal one-shot signal, then the maximum on-time of the synchronous MOSFET is obtained by subtracting the on-time of the primary switch from the one-shot signal duration. If the resistor is too small, the synchronous MOSFET may be turned off even when the secondary rectifier is still conducting, which decreases the system efficiency. However, if the resistor is too large, the output is shut off immediately once DET gets high. In SG6203, an internal phase-locked-loop (PLL) modulates the duration of the internal one-shot signal to maintain a suitable dead time between the primary switch and the synchronous MOSFET. The inverting input of the current sense comparator. In discontinuous conduction mode, the secondary rectifier turns off before the next switching cycle of the primary switch. Once the secondary rectifier is off, the synchronous MOSFET must be turned off to prevent the reversed energy flow. A resistor connected between IN+ and IN- can used to develop the zero current crossing signal of the secondary rectifier. Once the voltage on IN+ is lower than IN-, the output is pulled low. The non-inverting input of the current sense comparator. In discontinuous conduction mode, the secondary rectifier turns off before the next switching cycle of the primary switch. Once the secondary rectifier is off, the synchronous MOSFET must be turned off to prevent the reversed energy flow. A resistor connected between IN+ and IN- can used to develop the zero current crossing signal of the secondary rectifier. Once the voltage on IN+ is lower than IN-, the output is pulled low. 3 GND 4 VZ 5 DET 6 RT 7 IN- 8 IN+ (c) System General Corp. Version 1.0.1 (IAO33.0010.B1) -2- www.sg.com.tw * www.fairchildsemi.com September 24, 2007 Product Specification Synchronous Rectifier Controller for Flyback Converter SG6203 BLOCK DIAGRAM (c) System General Corp. Version 1.0.1 (IAO33.0010.B1) -3- www.sg.com.tw * www.fairchildsemi.com September 24, 2007 Product Specification Synchronous Rectifier Controller for Flyback Converter SG6203 ABSOLUTE MAXIMUM RATINGS Symbol VCC IOUT VH VL PD Parameter DC Supply Voltage* Gate Output Current DET, OUT, VZ RT, IN+, INPower Dissipation SOP8 DIP8 SOP8 DIP8 Value 25 500 -0.3 to 25.0 -0.3 to 7.0 400 800 208.4 82.5 150 -65 to +150 300 2.0 200 Unit V mA V V mW R JA TJ TSTG TL ESD Thermal Resistance (Junction-to-Air) Operating Junction Temperature Storage Temperature Range Lead Temperature (Soldering, 10 Seconds) Electrostatic Discharge Capability, Human Body Model Electrostatic Discharge Capability, Machine Model C/W C C C KV V * All voltage values, except differential voltages, are given with respect to GND pin. * Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. RECOMMENDED OPERATING CONDITIONS Symbol VCC TA RT Parameter DC Supply Voltage Operating Ambient Temperature Pulse Width of the One-shot Signal Value <20 -30~85 12~36 Unit V C K ELECTRICAL CHARACTERISTICS VCC=12V; RT=24K ; TA=25C, unless otherwise noted. Timing Control Section Symbol VRT Parameter Voltage on RT Pin Test Condition Min. 1.14 6.5 13 19.5 +40 Typ. 1.20 7.5 15 22.5 +60 Max. 1.26 8.5 17 25.5 +80 Unit V s s s % RT=12K TRT Pulse Width of the One-shot Signal RT=24K RT=36K TRT Adjustable Range of the Pulse Width Compared to TRT Timing Margin Between Output Turn-off (Output Falling) and Next Switching Cycle Start (DET Rising) RT=12K ; RT=24K ; RT=36K TDEAD 200 1000 ns (c) System General Corp. Version 1.0.1 (IAO33.0010.B1) -4- www.sg.com.tw * www.fairchildsemi.com September 24, 2007 Product Specification Synchronous Rectifier Controller for Flyback Converter SG6203 Min. 1.9 1.2 Synchronous Detection Section Symbol VTH VTL IDET TD_LOW Parameter Threshold Voltage to Enable One-shot Signal Threshold Voltage to Enable Output Current Output from DET Pin Debounce Time from DET Low to Enable Output Test Condition IN+ - IN- > 5mV RT=24K Typ. 2.1 1.4 250 Max. 2.3 1.6 300 300 Unit V V A ns 150 Current Detection Section Symbol VOFFSET IIN+ IINIIN+ - IINTP PSRR CMRR CMRR-f Parameter Offset Voltage Current Output from IN+ Current Output from INDifferential Current of IN+ and INPropagation Delay (OUTPUT from Low to High) Power Supply Rejection Ratio Common Mode Rejection Ratio Common Mode Rejection Ratio at 70KHz Test Condition RT=24K RT=24K 12K < RT < 36K DET< VTL, IN+ - IN- > 5mV Min. 90 90 Typ. 100 100 Max. 10 110 110 1.5 200 Unit mV A A A ns dB dB dB 65 65 32 Zener Section Symbol VZ Parameter Zener Voltage Test Condition IVZ=0.1 ~ 3mA Min. 18 Typ. 19 Max. 20 Unit V Output Section Symbol VOH Parameter Output Voltage High Test Condition VCC=12V, ISOURCE=50mA VCC=6V, ISOURCE=30mA VCC=12V, ISINK=50mA VCC=6V, ISINK=30mA TA=25C; CL=5nF, VCC=12V TA=25C; CL=5nF, VCC=12V Min. 11.2 3.5 Typ. Max. Unit V V VOL Tr Tf Output Voltage Low Rising Time Falling Time 1 1.2 150 150 175 175 V V ns ns VCC Section Symbol VOP ICC_OP VTH(ON) VTH(OFF) Parameter Continuously Operating Voltage Operating Current Start Threshold Minimum Operating Voltage Test Condition VDD=12V, Output=open, DET=50KHz, IN-=IN+=open, RT=12K Min. Typ. Max. 20 Unit V mA V V 1.7 6.0 4.8 5.1 4.0 6.3 (c) System General Corp. Version 1.0.1 (IAO33.0010.B1) -5- www.sg.com.tw * www.fairchildsemi.com September 24, 2007 Product Specification Synchronous Rectifier Controller for Flyback Converter SG6203 TYPICAL CHARACTERISTICS Start Threshold (VTH(ON)) vs Temperature 6.5 6.4 6.3 6.2 16.0 15.9 15.8 15.7 Pulse width of the one-shot signal (TRT) vs Temperature VTH(ON) (V) TRT(uS) 6.1 6.0 5.9 5.8 5.7 5.6 5.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 15.6 15.5 15.4 15.3 15.2 15.1 -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature () Temperature () Minimum Operating Voltage (VTH(OFF)) vs Temperature 5.85 5.80 5.75 5.70 Debounce time form DET low to enable the output (TD_LOW ) vs Temperature 350.0 300.0 250.0 VTH(OFF) (V) TD_LOW (nS) -40 -25 -10 5 20 35 50 65 80 95 110 125 5.65 5.60 5.55 5.50 5.45 5.40 5.35 200.0 150.0 100.0 50.0 0.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature () Temperature () Operating Current (ICC_OP) vs Temperature 2.0 1.8 1.6 Threshold voltage to enable an one shot signal (VTH) vs Temperature 1.842 1.840 1.838 ICC_OP(mA) 1.4 1.0 0.8 0.6 0.4 0.2 0.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 VTH(V) 1.2 1.836 1.834 1.832 1.830 1.828 -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature () Temperature () (c) System General Corp. Version 1.0.1 (IAO33.0010.B1) -6- www.sg.com.tw * www.fairchildsemi.com September 24, 2007 Product Specification Synchronous Rectifier Controller for Flyback Converter SG6203 Threshold voltage to enable the output (VTL) vs Temperature 1.56 1.54 1.52 VTL(V) 1.50 1.48 1.46 1.44 1.42 -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature () (c) System General Corp. Version 1.0.1 (IAO33.0010.B1) -7- www.sg.com.tw * www.fairchildsemi.com September 24, 2007 Product Specification Synchronous Rectifier Controller for Flyback Converter SG6203 OPERATION DESCRIPTION Synchronization The DET pin provides on/off information of the primary switch. As shown in the following reference circuits, one diode connected between the DET pin and the secondary winding of the transformer is used to get this information. Low DET voltage level indicates the secondary rectifier is conducted; therefore, the synchronous MOSFET should be turned on. The voltage on DET pin stays high when the primary switch is conducting and the synchronous MOSFET should be turned off. This innovative feature requires no auxiliary winding and the circuit complexity is greatly reduced. shut off immediately once DET gets high. In SG6203, an internal phase locked loop modulates the duration of the internal one-shot signal to maintain a suitable dead time between the primary switch and the synchronous MOSFET. The duration of the one-shot signal can be extended 80% compared with the original value decided by RT resistor. Current Sense In discontinuous conduction mode, the secondary rectifier turns off before the next switching cycle of the primary switch. Once the secondary rectifier is off, the synchronous MOSFET must be turned off to prevent the reverse energy flow. Therefore, a zero current crossing detector is needed when the converter is operated under DCM. The SG6203 provides two configurations to achieve this: output capacitor ESR method (reference Circuit-A) and current-sensing resistor method (reference Circuit-B). When the secondary rectifier is turned off, the voltage on IN+ is lower than that of IN-. Once this happens, the driving signal for the synchronous MOSFET is turned off. Anticipation and Phase Lock Loop A resistor from the RT pin to ground is used to determine the internal current source reference. When the primary switch is turned on with DET high, an internal one-shot timer outputs high for a duration proportional to the RT resistor. The duration of this one-shot signal can be expressed as: TRT = 15 x R T (K ) (s) 24 (1) Under-Voltage Lockout (UVLO) Primary Switch PWM One-Shot Signal T Output The SG6203 has an internal UVLO circuit with hysteresis. The IC is turned on if VCC is higher than 6V. Once turned on, SG6203 is turned off if VCC is lower than 5.1V. When the flyback output voltage is higher than 18V, the VZ pin can be used to provide a stable 18V to VCC pin. The on-time of the synchronous MOSFET is obtained by subtracting the on-time of the primary switch from the one-shot signal duration. If the resistor is too small, the synchronous MOSFET may be turned off when the secondary rectifier is still conducting, which decreases system efficiency. If the resistor is too large, the output is (c) System General Corp. Version 1.0.1 (IAO33.0010.B1) -8- www.sg.com.tw * www.fairchildsemi.com September 24, 2007 Product Specification Synchronous Rectifier Controller for Flyback Converter SG6203 REFERENCE CIRCUIT-A BOM Ref Des C2 C5 D1 D2 D3 Q1 R1 R2 R3 R4 R5 R6 R7 FR102 SB1100 1N4148 PSMN015-110P Part Number Description 0.1F 22pF 100V/1A 100V/1A 100V/0.2A 110V/75A; 15m 2.2K 22 47K 1.8K 2K 0 16.2K (c) System General Corp. Version 1.0.1 (IAO33.0010.B1) -9- www.sg.com.tw * www.fairchildsemi.com September 24, 2007 Product Specification Synchronous Rectifier Controller for Flyback Converter SG6203 REFERENCE CIRCUIT-B (c) System General Corp. Version 1.0.1 (IAO33.0010.B1) - 10 - www.sg.com.tw * www.fairchildsemi.com September 24, 2007 Product Specification Synchronous Rectifier Controller for Flyback Converter SG6203 PACKAGE INFORMATION 8 PINS-SOP(S) C 8 5 1 b 4 e D A1 A Dimensions Symbol A A1 b c D E e F H L Millimeter Min. Typ. 1.346 0.101 0.406 0.203 4.648 3.810 1.016 5.791 0.406 0 Max. 1.752 0.254 1.270 0.381X45 4.978 3.987 1.524 6.197 1.270 8 (c) System General Corp. Version 1.0.1 (IAO33.0010.B1) H F E L Inch Min. 0.053 0.004 Typ. Max. 0.069 0.010 0.016 0.008 0.183 0.150 0.040 0.228 0.016 0 0.196 0.157 0.060 0.244 0.050 8 0.050 0.015X45 - 11 - www.sg.com.tw * www.fairchildsemi.com September 24, 2007 Product Specification Synchronous Rectifier Controller for Flyback Converter SG6203 8PINS-DIP(D) D 8 5 X E1 E eB 1 4 A1 A2 L b1 b e Dimension Symbol A A1 A2 b b1 D E E1 e L eB Millimeter Min. 0.381 3.175 Inch Min. 0.015 0.125 Typ. A Max. 5.334 3.429 Typ. Max. 0.210 0.135 9.017 6.223 2.921 8.509 0 3.302 1.524 0.457 9.271 7.620 6.350 2.540 3.302 9.017 7 10.160 6.477 3.810 9.525 15 0.355 0.245 0.115 0.335 0 0.130 0.060 0.018 0.365 0.300 0.250 0.100 0.130 0.355 7 0.400 0.255 0.150 0.375 15 (c) System General Corp. Version 1.0.1 (IAO33.0010.B1) - 12 - www.sg.com.tw * www.fairchildsemi.com September 24, 2007 Product Specification Synchronous Rectifier Controller for Flyback Converter SG6203 (c) System General Corp. Version 1.0.1 (IAO33.0010.B1) - 13 - www.sg.com.tw * www.fairchildsemi.com September 24, 2007 |
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