CM6800

LOW START-UP CURRENT PFC/PWM CONTROLLER COMBO

GENERAL DESCRIPTION

The CM6800 is a controller for power factor corrected, switched mode power suppliers. Power Factor Correction (PFC) allows the use of smaller, lower cost bulk capacitors, reduces power line loading and stress on the switching FETs, and results in a power supply that fully compiles with IEC-1000-3-2 specifications.

Intended as a BiCMOS version of the industry-standard ML4824, CM6800 includes circuits for the implementation of leading edge, average current, “boost” type power factor correction and a trailing edge, pulse width modulator (PWM). Gate-driver with 1A capabilities minimizes the need for external driver circuits. Low power requirements improve efficiency and reduce component costs.

An over-voltage comparator shuts down the PFC section in the event of a sudden decrease in load. The PFC section also includes peak current limiting and input voltage brownout protection. The PWM section can be operated in current or voltage mode, at up to 250kHz, and includes an accurate 50% duty cycle limit to prevent transformer saturation.

CM6800 includes an additional folded-back current limit for PWM section to provide short circuit protection function.

FEATURES ‹

• Patent Number #5,565,761, #5,747,977, #5,742,151, #5,804,950, #5,798,635 ‹

• Pin to pin compatible with ML4800 and FAN4800 ‹

• Additional folded-back current limit for PWM section. ‹

• 23V Bi-CMOS process ‹

• VIN OK turn 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 ultra-fast PFC response ‹

• Low start-up current (100μ A typ.) ‹

• Low operating current (3.0mA type.) ‹

• Low total harmonic distortion, high PF ‹

• Reduces ripple current in the storage capacitor between the PFC and PWM sections ‹

• Average current, continuous or discontinuous boost leading edge PFC ‹

• VCC OVP Comparator, Low Power Detect Comparator ‹

• PWM configurable for current mode or voltage mode operation ‹

• Current fed gain modulator for improved noise immunity ‹

• Brown-out control, over-voltage protection, UVLO, and soft start, and Reference OK

APPLICATIONS

• ‹Desktop PC Power Supply ‹

• Internet Server Power Supply ‹

• IPC Power Supply ‹

• UPS ‹

• Battery Charger ‹

• DC Motor Power Supply ‹

• Monitor Power Supply ‹

• Telecom System Power Supply ‹

• Distributed Power

PIN CONFIGURATION

ABSOLUTE MAXIMUM RATINGS

Absolute Maximum ratings are those values beyond which the device could be permanently damaged.

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