Maker : System General
Part No. : SG6841

  Datasheet PDF : SG6841.pdf
  Cross Reference : SG6841 Cross Reference
  Buy Component : SG6841 Find Stock and Price

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Product Information

Product Specification High-integrated Green-mode PWM Controller SG6841 FEATURES 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 DESCRIPTION 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 RIN VIN RT RA RI SG6842 SENSE RS FB GND VDD GATE C IN D1 From auxiliary winding Rg Q1 RT RI ©System General Corp. Version 1.7 (IRO33.0001.B1) -1- www.sg.com.tw JUL.25,2003 Product Specification High-integrated Green-mode PWM Controller SG6841 MARKING DIAGRAMS 8 PIN CONFIGURATION T: D = DIP, S = SOP XXXXXXX: Wafer Lot YY: Year; WW: Week V: Assembly Location GND FB V IN Ri 1 2 3 4 8 7 6 5 G a te VDD S ense RT SG6841T XXXXXXXYYWWV 1 ORDERING INFORMATION Part Number SG6841S SG6841D Package 8-Pin SOP 8-Pin DIP PIN DESCRIPTIONS Pin No. 1 2 Symbol Function GND FB Ground 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 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 3 VIN Start-Up Input 4 Ri Reference Setting determined. Increasing the resistance will decrease the current source and reduce the switching frequency. A 26kΩ r esistor Ri creates a 50uA constant current Ii and generates 65kHz switching frequency. 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, t...

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