General Description

The CM6903B is a space-saving PFC-PWM controller for power factor corrected, switched mode power supplies that offers very low start-up and operating currents. For the power supply less than 500Watt, its input current shaping PFC performance could be very close to CM6800 or ML4800 architecture.

Power Factor Correction (PFC) offers the use of smaller, lower cost bulk capacitors, reduces power line loading and stress on the switching FETs, and results in a power supply fully compliant to IEC1000-3-2 specifications. The CM6903B includes circuits for the implementation of a leading edge, input current shaping technique ˇ§boostˇ¨ type PFC and a trailing edge, PWM.

The CM6903Bˇ¦s PFC and PWM operate at the same frequency, 67.5kHz. This higher frequency allows the user to design with smaller PWM components while maintaining the optimum operating frequency for the PFC. An PFC OVP comparator shuts down the PFC section in the event of a sudden decrease in load. The PFC section also includes peak current limiting for enhanced system reliability.

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Features

u          Patent Number #5,565,761, #5,747,977, #5,742,151, #5,804,950, #5,798,635 u          Pin to pin compatible with FAN6903/4 u          Enable lowest BOM for power supply with PFC u          Internally synchronized PFC and PWM in one IC u          Patented slew rate enhanced voltage error amplifier with advanced input current shaping technique u          Universal Line Input Voltage u          CCM boost or DCM boost with leading edge modulation PFC using Input Current Shaping Technique u          Feedforward IAC pin to do the automatic slope compensation u          PFCOVP, PFC VCCOVP, Precision -1V PFC ILIMIT, Tri-Fault Detect comparator to meet UL1950 u          No bleed resistor required u          Low supply currents; start-up: 100uA typical, operating current: 2mA typical. u          Synchronized leading PFC and trailing edge modulation PWM to reduce ripple current in the storage capacitor between the PFC and PWM sections and to reduce switching noise in the system u          VINOK Comparator to guarantee to enable PWM when PFC reach steady state u          High efficiency trailing-edge current mode PWM u          UVLO, REFOK, and brownout protection u          Digital PWM softstart: CM6903B (10ms) u         Precision PWM 1.5V current limit for current mode operation

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Applications

u          Desktop PC Power Supply

u          AC Adaptor

u          Internet Server Power Supply

u          IPC Power Supply

u          UPS

u          Battery Charger

u          DC Motor Power Supply

u          Monitor Power Supply

u          Telecom System Power Supply

u          Distributed Power

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Packages

• SIP-09

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Datasheet PDF file