Maker : System General
Part No. : SG6842

  Datasheet PDF : SG6842.pdf
  Cross Reference : SG6842 Cross Reference
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Product Information

Preliminary Specification Highly-Integrated Green-Mode PWM Controller www.DataSheet4U.com SG6842 zero-load conditions, the power supply enters burst-mode. This completely shuts off PWM output. Then, the output restarts just before the supply voltage, VDD, drops below the UVLO voltage. This green-mode function enables the power supply to easily meet international power conservation requirements. For improved power conversion efficiency, the SG6842 series is manufactured using the BiCMOS process. This allows the start-up current to be reduced to 20uA, and the operating current to be reduced to 4mA. For even higher power conversion efficiency, a large start-up resistance can be used. Built-in synchronized slope compensation ensures the stability of peak current mode control. Proprietary internal compensation ensures constant output power limiting over a universal range of AC input voltages, from 90VAC to 264VAC. SG6842 controllers provide many protection functions. Pulse-by-pulse current limiting ensures a constant output current, even when short circuits occur. Should an open circuit failure occur in the feedback loop, the internal protection circuit will disable PWM output. PWM output will be disabled as long as VDD remains higher than 26V. 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. When either over temperature conditions or VDD over voltage faults are detected, an internal latch circuit is used to latch-off the controller. The latch will reset when the temperature cools off sufficiently, or when the VDD power supply is disabled. SG6842 series controllers are available in both 8-pin DIP and SO packages. D1 C IN VDD Rg GATE Q1 From auxiliary winding FEATURES Linearly decreasing PWM frequency Burst-mode at light load and zero load Low start-up current (20uA) Low operating current (4mA) Internal latch circuit for OTP, OVP Leading-edge blanking Built-in synchronized slope compensation Totem pole output with soft driving Improved EMI Constant power limit over a universal AC input range Current mode operation Cycle-by-cycle current limiting Under Voltage Lockout (UVLO) Programmable PWM frequency GATE output maximum voltage clamped at 18V VDD Over Voltage Protection (OVP) Programmable Over Temperature Protection (OTP) Very few external components are required APPLICATIONS General-purpose switch mode power supplies and flyback power converters, including: Power adapters Open-frame SMPS Battery Charger Adapter DESCRIPTION The highly integrated SG6842 series of PWM controllers provides several features to enhance the performance of flyback converters. To minimize standby power consumption, a proprietary green-mode function provides off-time modulation to linearly decrease the switching frequency under light-load conditions. Under TYPICAL APPLICATION From bridge rectifier 127~ 373VDC RIN VIN RT RA RI SG6842 SENSE RI FB GND RT RS © System General Corp. Version 0.1(IRO33.0009.B0) -1- www.sg.com.tw Apr.09, 2003 Preliminary Specification Hww.DataSheet4U.com w ighly-Integrated Green-Mode PWM Controller SG6842 PIN CONFIGURATION MARKING DIAGRAMS 8 B: B = Linearly Decreasing Frequency + Burst-Mode: Null = Linear F: L = OTP Latch: The pin is reset when AC is disconnected. C = Hysteresis OTP : The pin is reset when the temperature cools down. V: V = OVP Latch T: D = DIP, S = SOP XXXXXXX: Wafer Lot YY: Year; WW: Week V: Assembly Location SG6842BFVT XXXXXXXYYWWV GND FB VIN RI 1 2 3 4 8 7 6 5 GATE VDD SENSE RT 1 ORDERING INFORMATION The SG6842 family of controllers is distinguished for its protection features and burst-mode functionality. Green-Mode Function: Linearly Decreasing Frequency and Burst-Mode Hysteresis OTP: OVP Latch: OTP Latch: Reset when the Reset when AC is Reset when AC is temperature cools down unplugged (L). unplugged (V). (C). Part Number Package SG6842BS SG684...

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