Part Number : CR6842
Function : Green Power PWM Controller
Manufactures : Chip Rail
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Description :
CR6842 Green-Power PWM Controller with Freq. Jittering Features z z z z z z z z z z z Low Cost, Green-Power Burst-Mode PWM Very Low Start-up Current ( about 7.5µA) Low Operating Current ( about 3.0mA) Current Mode Operation Under Voltage Lockout (UVLO) VDD Over Voltage Protection(OVP) programmable over-temperature protection Internal Latch Circuit(OTP,OVP) Built-in soft start with 1ms Built-in Frequency jitter for better EMI Signature Soft Clamped gate output voltage 16.5V z z z z z z z z z z VDD over voltage protect 25.5V Cycle-by-cycle current limiting Sense Fault Protection Output SCP (Short circuit Protection) Built-in Synchronized Slope Compensation Leading-edge blanking on Sense input Programmable PWM Frequency High-Voltage CMOS Process with ESD DIP-8 & SOP-8 Pb-Free Package Compatible with SG6842J&LD7552&OB2269 Applications z z Power Adaptor Battery Charger Adapter z z Open Frame Switching Power Supply LCD Monitor General Description The CR6842 is a low startup current , low cost, current mode PWM controller with Green-Power & burst-mode power-saving operation. The integrated functions such as the leading-edge blanking of the current sensing, internal slope compensation provide the users a high efficiency, low external component counts, and low cost solution for AC/DC power applications. The special Green-Power function provides off-time modulation to linearly decrease the switching frequency under light-load conditions. And under zero-load conditions, the power supply enters burst-mode to further reduce power consumption by shutting off PWM output. When the output of power supply is short or over loaded, the FB voltage will increase ,and if the FB voltage is higher than 5.2V for longer than 56msec the PWM output will be turned off. A external NTC resistor connected from pin RT to ground can be applied to over-temperature protection. Pulse by pulse current limit ensures a constant output current even under short circuit. PWM output will be disabled as long as VDD exceeds a threshold. When internal latch circuit is used to latch-off the controller, the latch will be reset when the power supply VDD is disabled. Dec.2006 V 1.3 1 Chengdu Chip-Rail Tech.Co.,Ltd CR6842 Pin Assignment & Description 1 2 3 4 GND FB VIN RI GATE VDD SENSE RT 8 7 6 5 Name GND FB VIN RI RT SENSE VDD GATE Description GND Pin Voltage feedback pin. The PWM duty cycle is determined by FB and Sense. This pin is pulled high to the rectified line input through a large resistor for start-up. This pin is also used to detect line voltage to compensate for constant output power limit for universal AC input. By connecting a resistor to ground to set the switching freq.. Increasing the resistor will reduce the switching freq.. An NTC resistor is connected from this pin to ground for over-temperature protection. Current sense pin, The sensed voltage is used for current-mode control and pulse-by-pulse current limiting. Power supply […]
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