Current Mode PWM Controller 9-Pin SOIC T/R

The NCP1249 is a highly integrated high-voltage PWM controller capable of delivering a rugged and high performance offline power supply with extremely low no-load consumption. With a supply range up to 30 V, the controller hosts a jittered 65-kHz switching circuitry operated in peak current mode control. When the power on the secondary side starts to decrease, the controller automatically folds back its switching frequency down to a minimum level of 26 kHz. As the power further goes down, the part enters skip cycle while freezing the peak current setpoint. To help build rugged converters, the controller features several key protective features: an internal brown-out, a non-dissipative Over Power Protection for a constant maximum output current regardless of the input voltage and two latched over voltage protection inputs - either through a dedicated pin or via the Vcc input. The controller architecture is arranged to authorize a transient peak power excursion when the peak current hits the limit. At this point, the switching frequency is increased from 65 kHz to 130 kHz until the peak requirement disappears. The timer duration is then modulated as the converter crosses a peak power excursion mode (long) or undergoes a short circuit (short). Similar to NCP1255 & NCP1254 with integrated HV Startup NCP1249 has Active ON (A&B) and Active OFF (C&D) versions.

• High-voltage Current Source for Lossless Start-up Sequence
• Remote Input for Standby Operation Control
• Automatic and Lossless X2 Capacitors Discharge Function
• 65-kHz Fixed-frequency Current-mode Control Operation with 130-kHz Excursion
• Internal and Adjustable Over Power Protection (OPP) Circuit
• Internal Brown-Out Protection Circuit
• Frequency Foldback down to 26 kHz and Skip-cycle in Light Load Conditions
• Adjustable Ramp Compensation
• Internally Fixed 4-ms Soft-start
• 100% to 25% Timer Reduction from Overload to Short-circuit Fault
• Frequency Jittering in Normal and Frequency Foldback Modes
• Latched OVP Input for Improved Robustness and Latched OVP on Vcc
• Up to 30 V Vcc Maximum Rating
• +300 mA/ -500 mA Source/Sink Drive Capability
• Extremely Low No-load Standby Power
• Option for Auto-Recovery or Latched Short-Circuit Protection
• Internal Thermal Shutdown with Hysteresis
• These are Pb-Free Devices