Mixed Frequency Mode Greenline PWM Controller:
Fixed Frequency, Variable Frequency, Standby Mode

The MC44603 is an enhanced high performance controller that is specifically designed for off–line and dc–to–dc converter applications. This device has the unique ability of automatically changing operating modes if the converter output is overloaded, unloaded, or shorted, offering the designer additional protection for increased system reliability. The MC44603 has several distinguishing features when compared to conventional SMPS controllers. These features consist of a foldback facility for overload protection, a standby mode when the converter output is slightly loaded, a demagnetization detection for reduced switching stresses on transistor and diodes, and a high current totem pole output ideally suited for driving a power MOSFET. It can also be used for driving a bipolar transistor in low power converters (< 150 W). It is optimized to operate in discontinuous mode but can also operate in continuous mode. Its advanced design allows use in current mode or voltage mode control applications.

Current or Voltage Mode Controller
• Operation up to 250 kHz Output Switching Frequency
• Inherent Feed Forward Compensation
• Latching PWM for Cycle–by–Cycle Current Limiting
• Oscillator with Precise Frequency Control

High Flexibility
• Externally Programmable Reference Current
• Secondary or Primary Sensing
• Synchronization Facility
• High Current Totem Pole Output
• Undervoltage Lockout with Hysteresis

Safety/Protection Features
• Overvoltage Protection Against Open Current and Open Voltage Loop
• Protection Against Short Circuit on Oscillator Pin
• Fully Programmable Foldback
• Soft–Start Feature
• Accurate Maximum Duty Cycle Setting
• Demagnetization (Zero Current Detection) Protection
• Internally Trimmed Reference

GreenLine Controller: Low Power Consumption in Standby Mode
• Low Startup and Operating Current
• Fully Programmable Standby Mode
• Controlled Frequency Reduction in Standby Mode
• Low dV/dT for Low EMI Radiations