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The CM6800 is a controller for power factor-corrected switch mode power supplies. Power Factor Correction (PFC) allows smaller, lower-cost bulk capacitors, reducing power line loading and stress on switching FETs. The CM6800 includes circuits for implementing leading edge, average current, "boost" type power factor correction and trailing edge, and pulse width modulator (PWM). A 1A capable gate driver minimizes the need for external driver circuitry. Low power requirements increase efficiency and reduce component costs.
In case of a sudden load drop in this controller, the overvoltage comparator turns off the PFC section. The PFC section also includes peak current limiting and input voltage brownout protection. The PWM section can operate in current or voltage mode up to 250kHz and includes an accurate 50% duty cycle limit to prevent transformer saturation. The CM6800 also includes an additional PWM section foldback current limit for short-circuit protection.
Feature:
• Pin Compatible with ML4800 and FAN4800
• Additional foldback current limit for the PWM section.
• 23V Bi-CMOS process
• VIN OK turns on PWM at 2.5V instead of 1.5V
• Internally synchronized leading edge PFC and trailing edge PWM in one IC
• Slew Rate Enhanced Transconductance Error Amplifier for Ultrafast PFC Response
• Low startup current (100uA typical)
• Low operating current (3.0mA type)
• Low THD, high PF
• Reduces ripple current in storage capacitor between PFC and PWM sections
• Average current, continuous or discontinuous boost leading edge PFC
• VCC OVP comparator, low power detection comparator
• PWM configurable for current mode or voltage mode operation
• Current-fed gain modulator for improved noise immunity
• Undervoltage control, overvoltage protection, UVLO and soft start
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