Product Specification SG6841 High-integrated Green-mode PWM Controller FEATURES DESCRIPTION Green-mode PWM to support “Blue Angel” Norm Low start up current 30uA Low operation current 3mA Leading-edge blanking Built-in synchronized slope compensation Constant output power limit for universal AC input Current mode operation Cycle-by-cycle current limiting Under voltage lockout (UVLO) Programmable PWM frequency GATE output maximum voltage clamped at 18V Totem pole output includes soft driving for better EMI Build-in limited-power-control to meet safety requirement Programmable over-temperature protection Few external components & low cost solution This highly integrated PWM controllers, SG6841 series, provides several features to enhance the performance of low power flyback converters. To minimize standby power consumption, the proprietary green-mode function provides off-time modulation to linearly decrease the switching frequency under light-load conditions. This green-mode function assists the power supply to easily meet the power conservation requirement. Due to BiCMOS process, the start-up current and operation current is reduced to 30uA and 3mA, respectively, to improve power conversion efficiency. Large start-up resistance can be used for further power saving. Built-in synchronized slope compensation ensures the stability of peak current mode control. A proprietary internal compensation ensures constant output power limit for universal AC input voltage from 90VAC to 264VAC. SG6841 provides many protection functions. Pulse by pulse current limit ensures a constant output current under short circuit. If a short circuit failure or over load happens, the SG6841 will shut off after a continuous high voltage detection on FB pin. The gate output is clamped at 18V to protect the power MOS from over voltage damage. An external NTC thermistor can be applied to sense the ambient temperature for over-temperature protection. The SG6841 series are available in 8-pin DIP and SO packages. APPLICATIONS General-purpose switching mode power supplies and flyback power converters, and Power Adapter Open-frame SMPS Battery Charger Adapter TYPICAL APPLICATION From bridge rectifier 127~ 373VDC D1 RIN C IN VIN RT VDD From auxiliary winding Rg Q1 GATE RA RI RT RI Version 2.1 (IRO33.0001.B5) SENSE RS FB ©System General Corp. SG6842 GND -1- www.sg.com.tw Jun.15,2006 Product Specification SG6841 High-integrated Green-mode PWM Controller MARKING DIAGRAMS PIN CONFIGURATION T: D = DIP, S = SOP P: Z = Lead Free SG6841TP Null=regular package XXXXXXXYYWWV XXXXXXX: Wafer Lot GND GATE FB VDD VIN YY: Year; WW: Week V: Assembly Location RI SENSE RT ORDERING INFORMATION Part Number Package SG6841S 8-Pin SOP SG6841D 8-Pin DIP SG6841SZ 8-Pin SOP(Lead Free) SG6841DZ 8-Pin DIP(Lead Free) PIN DESCRIPTIONS Pin No. Symbol Function 1 GND Ground 2 FB Feedback Description Ground. The signal from external compensation circuit is feed into this pin. The PWM duty cycle is determined by this FB pin and current sense signal from Pin 6. This pin is pulled high to the rectified line input through a resistor for start-up. Since the 3 VIN Start-Up Input start-up current requirement for SG6841 is very small, a large start-up resistance can be used to minimize power loss. Under normal operation, this pin is also used to detect line voltage to compensate for constant output power limit for universal AC input. A resistor from RI pin to ground will generate a constant current source forSG6841. This current is used to charge an internal capacitor and hence the switching frequency are 4 Ri Reference Setting determined. Increasing the resistance will decrease the current source and reduce the switching frequency. A 26kΩ resistor Ri creates a 50uA constant current Ii and generates 65kHz switching frequency. 5 RT Temperature Protection 6 SENSE Current Sense 7 VDD Power supply 8 GATE Driver Output ©System General Corp. Version 2.1 (IRO33.0001.B5) For over-temperature protection. An external NTC thermistor is connected from this pin to ground. The impedance of the NTC will decrease under high temperature. Once the voltage on RT pin drops below a fixed limit, the PWM output will be disabled. Current sense. The sensed voltage is used for current mode control and pulse-by-pulse current limiting. Power Supply. The totem-pole output driver for the power MOSFET. A soft driving waveform is implemented to improve EMI. -2- www.sg.com.tw Jun.15,2006 Product Specification SG6841 High-integrated Green-mode PWM Controller BLOCK DIAGRAM RI 4 VDD 0.85V VIN ON/OFF Driver + 3 _ Internal BIAS VDD + 7 Q OSC S 8 GATE 6 SENSE 2 FB Green Mode Controller R UVLO _ 16V/10V Comp Slope Compensation 2R I RT RT 6V 5 Limited Power Controller + _ Comp R 4.2V 0.65V 1 GND ©System General Corp. Version 2.1 (IRO33.0001.B5) -3- www.sg.com.tw Jun.15,2006 Product Specification SG6841 High-integrated Green-mode PWM Controller ABSOLUTE MAXIMUM RATINGS Symbol Parameter Value Unit DC Supply Voltage 30 V Zener clamp 32 V Zener current 10 mA IOUT Gate Output Current 500 mA VFB Input Voltage to FB Pin -0.3 to 7V V VSense Input Voltage to SENSE Pin -0.3 to 7V V VRT Input Voltage to RT Pin -0.3 to 7V V VRI Input Voltage to Ri Pin -0.3 to 7V V PD Power Dissipation 1 W DIP 82.5 °C /W SOP 141 VDD Thermal Resistance Junction-air RΘ j-a TJ Operating Junction Temperature 150 °C TA Operating Ambient Temperature -30 to 85 °C Tstg Storage Temperature Range -55 to +150 °C TL Lead Temperature (Wave soldering or IR, 10 seconds) ESD Capability, HBM model 260 3.0 °C KV ESD Capability, Machine model 250 V RECOMMENDED OPERATING CONDITIONS Symbol Parameter Value Unit VDD DC Supply Voltage <20 V TA Operating Ambient Temperature -20 to +85 ℃ RI Current source Setting 26 KΩ ELECTRICAL CHARACTERISTICS Feedback Input Section Symbol Parameter Min. Typ. Max. Unit AV Input-voltage to current-sense attenuation 1/3.25 1/3 1/2.75 V/V ZFB Input impedance 2 4.5 8 KΩ IFB Bias current 2 mA VOZ Input voltage for zero duty cycle 1.2 V ©System General Corp. Version 2.1 (IRO33.0001.B5) Test Condition -4- www.sg.com.tw Jun.15,2006 Product Specification SG6841 High-integrated Green-mode PWM Controller Current Sense Section Symbol Parameter ZCS Input impedance TPD Delay to Output VTH Threshold voltage for current limit ΔVTH @ IVIN The change of threshold voltage versus the input current of the Vin Test Condition Min. Typ. Max. Unit 8 12 16 KΩ 150 200 ns IVIN = 0 uA 0.8 0.85 0.9 V IVIN = 220 uA -0.09 -0.15 -0.21 V 0.73 0.81 0.89 VSENSE0 Threshold voltage for IVIN = 80uA IVIN = 80 uA Tdelay-lps The delay time of limited-power-control RI=26KOhms V 31 ms Oscillator Section Symbol Parameter Test Condition Min. Typ. Max. Unit FOSC Frequency in nominal mode RI=26KOhms 60 65 70 KHz Fosc-green Frequency in green mode RI=26KOhms 10 16 VG End of green mode voltage at FB pin KHz 1.4 VN Beginning of frequency reducing at FB pin SG Slope for green mode modulation RI=26KOhms FDV Frequency variation versus VDD deviation FDT Frequency variation versus Temp. deviation V 2.1 50 80 V 120 Hz/mV VDD=10 to 20V 5 % TA=-30 to 85 ℃ 5 % PWM Section Symbol Parameter Test Condition Min. Typ. Max. Unit DC (MAX) Maximum Duty Cycle 75 80 90 % DC (MIN) Minimum Duty Cycle - - 0 % Bnk Leading edge blanking time 200 270 350 ns Min. Typ. Max. Unit Output Section Symbol Parameter Test Condition VOL Output Voltage Low VDD = 12V, Io = 150mA VOH Output Voltage High VDD = 12V, Io = 50mA 8V tr Rising Time VDD =13V, CL=1nF 150 250 350 ns tf Falling Time VDD =13V, CL=1nF 30 50 90 ns Test Condition 1.5 V V Under-voltage Lockout Section Symbol Parameter Min. Typ. Max. Unit VTH(ON) Start Threshold Voltage 15 16 17 V VDD(min) Min. Operating Voltage 9 10 11 V ©System General Corp. Version 2.1 (IRO33.0001.B5) -5- www.sg.com.tw Jun.15,2006 Product Specification SG6841 High-integrated Green-mode PWM Controller Over-Temperature Protection Section Symbol Parameter Test Condition Min. Typ. Max. Unit IRT Output current of pin RT RI=26KOhms 92 100 108 uA VOTP,STOP Threshold voltage for over-temperature protection. 0.585 0.62 0.655 V Turn-off point. Duty cycle is reduced to 0%. VOTP,START Threshold voltage for over-temperature protection. 0.65 V Starting point. Duty cycle starts to decrease. Total Standby Current Section Symbol Parameter Test Condition IDD ST IDD OP Start-up Current Operating Supply Current VDD=14.5V FB=SENSE=0V GATE=1000pF VDD=15.5V ©System General Corp. Version 2.1 (IRO33.0001.B5) -6- Min. Typ. Max. Unit 30 3 40 5 uA mA www.sg.com.tw Jun.15,2006 Product Specification SG6841 High-integrated Green-mode PWM Controller TYPICAL CHARACTERISTICS Start-up Current (IDD ST) vs VDD Voltage 25.5 35 25.0 30 Start-up Current (uA) Start-up Current (uA) Start-up Current (IDD ST) vs Tem perature 24.5 24.0 23.5 23.0 22.5 22.0 25 20 15 10 5 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 0 2 4 6 TEMPERATURE (℃ ) 8 10 12 14 16 VDD VOLTAGE (V) Frequency vs. FB Voltage Frequency in green mode (Fosc-green) vs Temperature 70 10.52 10.50 50 Fosc-green (KHz) Frequency (KHz) 60 40 30 20 10 0 1.1 1.4 1.7 2 2.3 2.6 10.48 10.46 10.44 10.42 10.40 10.38 10.36 10.34 2.9 -40 -25 -10 5 FB VOLTAGE (V) 20 35 50 65 80 95 110 125 TEMPERATURE (℃) PWM Oscillator Frequency (Fosc) vs Tem perature Maximum Duty Cycle DC(MAX.)vs Temperature 64.4 Max. Duty Cycle (%) Fosc (KHz) 64.3 64.2 64.1 64.0 63.9 63.8 63.7 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 TEMPERATURE (℃ ) ©System General Corp. Version 2.1 (IRO33.0001.B5) 84.75 84.70 84.65 84.60 84.55 84.50 84.45 84.40 84.35 84.30 84.25 84.20 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (℃) -7- www.sg.com.tw Jun.15,2006 Product Specification SG6841 High-integrated Green-mode PWM Controller Min. Operating Voltage (V DD(min)) vs Tem perature Start Threshold Voltage (V TH(ON)) vs Tem perature 16.60 16.55 16.50 10.10 10.05 10.00 VTH(ON) (V) VDD(min) (V) 10.20 10.15 9.95 9.90 9.85 9.80 16.45 16.40 16.35 16.30 9.75 9.70 16.25 -40 -25 -10 5 20 35 50 65 80 95 110 125 16.20 -40 TEMPERATURE (℃ ) -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (℃ ) RT Voltage vs Ton Output Current of pin RT (IRT) vs Temperature 14 12 101.5 101.0 8 IRT (uA) Ton (uS) 10 6 4 2 100.5 100.0 99.5 99.0 0 -2 0.620 98.5 0.628 0.636 0.644 0.652 0.660 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (℃) RT VOLTAGE (V) V OTP, STOP vs Tem perature VSENSE vs IVIN 0.63 0.84 0.79 0.74 0.62 VSENSE VOTP, STOP (V) 0.62 0.61 0.69 0.64 0.59 0.61 0.54 0.60 0.49 0.44 0.60 -40 -25 -10 5 20 35 50 65 80 95 110 0 125 TEMPERATURE (℃ ) ©System General Corp. Version 2.1 (IRO33.0001.B5) -8- 40 80 120 160 200 IVIN (uA) 240 280 320 360 www.sg.com.tw Jun.15,2006 Product Specification SG6841 High-integrated Green-mode PWM Controller OPERATION DESCRIPTION Current sensing and PWM current Start-up current limiting Typical start-up current is only 30uA so that a high resistance, and low-wattage, start-up resistor can be used to minimize power loss. For an AC/DC adapter with universal input range, a 1.5 MΩ, 0.25W, start-up resistor and a 10uF/25V VDD hold-up capacitor are enough for this application. Peak current mode control is utilized in SG6841 to regulate output voltage and provide pulse by pulse current limiting. The switch current is detected by a sense resistor into the sense pin of SG6841. The PWM duty cycle is determined by this current sense signal and VFB, the feedback voltage. When the voltage on sense pin reaches VCOMP = (VFB–1.0)/3, a switch cycle will be terminated immediately. VCOMP is internally clamped to a variable voltage around 0.85v for output power limit. Operating current Operating current has been reduced to 3mA. The low operating current enables a better efficiency and reduces the requirement of VDD hold-up capacitance. Leading Edge Blanking Each time when the power MOSFET is switched on, a turn-on spike will inevitably occur on the sense-resistor. To avoid premature termination of the switching pulse, a 270 nsec leading-edge blanking time is built in. Conventional RC filtering can therefore be omitted. During this blanking period, the current-limit comparator is disabled and it cannot switch off the gate driver. Green Mode Operation The patented green-mode function provides an off-time modulation to reduce the switching frequency in the light load and no load conditions. The on time is limited for better abnormal or brownout protection. VFB, which is derived from the voltage feedback loop, is taken as the reference. Once VFB is lower than the threshold voltage, switching frequency will be linearly decreased to the minimum green mode frequency around 10kHz (Ri =26kΩ). Under-voltage lockout (UVLO) The turn-on and turn-off threshold of SG6841 are fixed internally at 16V/10V. During start-up, the hold-up capacitor must be charged to 16V through the start-up resistor so that SG6841 will be enabled. The hold-up capacitor will continue to supply VDD before the energy can be delivered from auxiliary winding of the main transformer. VDD must not drop below 10V during this start-up process. This UVLO hysteresis window insures that hold-up capacitor is adequate to supply VDD during start-up. Oscillator Operation A resistor from RI pin to ground will generate a constant current source for SG6841. This current is used to charge an internal capacitor and hence the internal clock and switching frequency are determined. Increase the resistance will decrease the current source and reduce the switching frequency. A 26kΩ resistor Ri creates a 50uA constant current Ii and generates 65kHz switching frequency. The relation between Ri and switching freauency is: fPWM = 1690 RI (kΩ ) Gate Output / Soft Driving The SG6841 BiCMOS output stage is a fast totem pole gate driver. Cross conduction has been avoided to minimize heat dissipation, increases efficiency and enhances reliability. The output driver is clamped by an internal 18V Zener diode in order to protect power MOSFET transistors against undesirable gate over voltage. A soft driving waveform is implemented to minimize EMI. (kHz ) ---------------------------- (1) The range of the PWM oscillation frequency is designed as 50kHz ~ 90kHz. ©System General Corp. Version 2.1 (IRO33.0001.B5) -9- www.sg.com.tw Jun.15,2006 Product Specification SG6841 High-integrated Green-mode PWM Controller Built-in Slope Compensation The sensed voltage across the current sense resistor is used for current mode control and pulse-by-pulse current limiting. Built-in slope compensation will improve stability or prevent sub-harmonic oscillation of peak current mode control. SG6841 inserts a synchronized positive-going ramp at every switching cycle. Vs-comp = 0.33V. Constant Output Power Limit When the SENSE voltage, across the sense resistor Rs, reaches the threshold voltage, around 1.0V, the output GATE drive will be turned off after a small propagation delay tD. This propagation delay will introduce an additional current proportional to tD*Vin/Lp. Since the propagation delay is nearly constant regardless of the input line voltage VIN. Higher input line voltage will result in a larger additional current and hence the output power limit is also higher than that under low input line voltage. To compensate this variation for wide AC input range, the threshold voltage is adjusted by the VIN current. Since VIN pin is connected to the rectified input line voltage through the start-up resistor, a higher line voltage will generate higher VIN current into the VIN pin. The threshold voltage is decreased if the VIN current is increased. Smaller threshold voltage, forces the output GATE drive to terminate earlier, thus reduce the total PWM turn-on time and make the output power equal to that of low line input. This proprietary internal compensation ensures a constant output power limit for wide AC input voltage from 90VAC to 264VAC. At high ambient temperature, Rntc will be smaller such that VRT will decrease. When VRT is less than 0.65V (VOTP,START), the PWM duty cycle will be decreased to lower the internal temperature of power supply. If the over heating situation still exists such that VRT decreases further to 0.62V (VOTP,STOP), the PWM will be completely turned off. Limited Power Control Every time when the output of power supply is shorted or over loaded, the FB voltage will increase. If the FB voltage is higher than a designed threshold, 4.2V, for longer than 31msec, the PWM output will then be turned off eternally. VDD, the supply voltage for SG6841, will decrease due to the supply current for SG6841. When VDD is lower than the turn-off threshold such as 10V, SG6841 will be totally shut down. Due to the start up resistor, VDD will be charged up to the turn-on threshold voltage 16V until SG6841 is enabled again. If the over loading condition still exists, above protection will take place repeatedly. This will prevent the power supply from being overheated under over loading condition. Noise immunity Noise on the current sense or control signal may cause significant pulse width jitter, particularly in the continuous conduction mode. Slope compensation helps alleviate this problem. Good placement and layout practices should be followed. Avoiding long PCB traces and component leads, locating compensation and filter components near to the SG6841, and increasing the power MOS gate resistance will always help. Thermal Protection An NTC thermistor Rntc in series with a resistor Ra can be connected from pin RT to ground. A constant current IRT is output from pin RT. The voltage on RT pin can be expressed as VRT = IRT × (Rntc + Ra) in which IRT = 2 x (1.3V / Ri). ©System General Corp. Version 2.1 (IRO33.0001.B5) - 10 - www.sg.com.tw Jun.15,2006 Product Specification SG6841 High-integrated Green-mode PWM Controller REFERENCE CIRCUIT Circuit 2 F1 L1 2 C1 R2 3 1 L2 4 C2 2 BD1 4 1 3 1 R1 4 2 C3 + C4 R3 1,2 1,2 8,9 1 3 8,9 Q1 L3 2 1 2 Vo+ 1 1 2 VZ1 THER1 D2 R5 3 4 2 C5 D1 R4 C6 C7 3 4 + C8 2 U1 2 3 4 GND FB VDD VIN RI SENSE RT 8 Q2 1 7 5 5 6,7 R6 6,7 6 5 R8 SG6841 R11 R10 R12 2 R9 GATE 3 1 D3 2 R7 + 1 3 1 2 1 2 3 1 CN1 THER2 + 1 D4 2 C9 1 U2 1 3 2 3 4 R13 U3 C10 R14 1 Vo+ 2 R15 BOM Reference Component Reference Component BD1 BD 4A/600V R1,R2 R 1Mohm 1/4W C1 XC 0.1uF/275V R3 R 100Kohm 1/2W C2 XC 0.22uF/275V R4 R 47ohm 1/4W C3 CC 0.01uF/500V R5,R7 R 750Kohm 1/4W C4 EC 120u/400V R6 R 20Kohm 1/8W C5 YC 222p/Y1 R8 R 0.3ohm 2W C6 CC 1000pF/100V R9 R 33Kohm 1/8W C7 CC 1000pF/50V R9 R 20Kohm 1/8W 1% C8 EC 1000uF/35V R11 R 220ohm 1/8W C9 EC 220uF/35V R12 R 4.7ohm 1/8W D1 LED R13 R 6.8Kohm 1/8W D2 Diode FR157 R14 R 154Kohm 1/8W D3 ZD 18V R15 R 390Kohm 1/8W D4 Diode FR102 THER1 Thermistor SCK054 F1 FUSE 4A/250V T1 Transformer L1 900uH U1 IC SG6841 L2 15mH U2 IC PC817 Q1 Diode 20A100V U3 IC TL431 Q2 MOS 7A/600V VZ1 VZ 9G ©System General Corp. Version 2.1 (IRO33.0001.B5) - 11 - www.sg.com.tw Jun.15,2006 Product Specification SG6841 High-integrated Green-mode PWM Controller PACKAGE INFORMATION 8 PINS– DIP (D) D Θ° 5 E1 8 B A A2 4 A1 1 e E L b1 b e Dimension Symbol A A1 A2 b b1 D E E1 e L eB θ° ©System General Corp. Version 2.1 (IRO33.0001.B5) Millimeter Min. 0.381 3.175 9.017 6.223 2.921 8.509 0° Inch Min. Typ. Max. 5.334 3.302 1.524 0.457 9.271 7.620 6.350 2.540 3.302 9.017 7° 3.429 0.015 0.125 10.160 0.355 6.477 0.245 3.810 9.525 15° 0.115 0.335 0° - 12 - Typ. Max. 0.210 0.130 0.060 0.018 0.365 0.300 0.250 0.100 0.130 0.355 7° 0.135 0.400 0.255 0.150 0.375 15° www.sg.com.tw Jun.15,2006 Product Specification SG6841 High-integrated Green-mode PWM Controller 8 PINS– SOP (S) 8 C 5 H E F 1 4 b e D Θ L A A1 Dimension Symbol A A1 b c D E e F H L θ° Millimeter Min. 1.346 0.101 ©System General Corp. Version 2.1 (IRO33.0001.B5) Typ. Max. 1.752 0.254 Inch Min. 0.053 0.004 0.406 0.203 4.648 0.381 Max. 0.069 0.010 0.016 0.008 4.978 3.987 0.183 0.150 1.270 0.196 0.157 0.050 0.381X45° 5.791 0.406 0° Typ. 0.015X45° 6.197 1.270 8° - 13 - 0.228 0.016 0° 0.244 0.050 8° www.sg.com.tw Jun.15,2006 Product Specification SG6841 High-integrated Green-mode PWM Controller DISCLAIMERS LIFE SUPPORT System General’s products are not designed to be used as components in devices intended to support or sustain human life. Use of System General’s products in components intended for surgical implant into the body, or other applications in which failure of the System General’s products could create a situation where personal death or injury may occur, is not authorized without the express written approval of System General’s Chief Executive Officer. System General will not be held liable for any damages or claims resulting from the use of its products in medical applications. MILITARY System General's products are not designed for use in military applications. Use of System General’s products in military applications is not authorized without the express written approval of System General’s Chief Executive Officer. System General will not be held liable for any damages or claims resulting from the use of its products in military applications. RIGHT TO MAKE CHANGES System General reserves the right to change this document and/or this product without notice. Customers are advised to consult their System General sales representative before ordering. ©System General Corp. Version 2.1 (IRO33.0001.B5) - 14 - www.sg.com.tw Jun.15,2006