The NCP1377 combines a true current mode modulator and a demagnetization detector which ensures full borderline/critical Conduction Mode in any load/line conditions together with minimum drain voltage switching (Quasi−Resonant operation). Due to its inherent skip cycle capability, the controller enters burst mode as soon as the power demand falls below a predetermined level. As this happens at low peak current, no audible noise can be heard. For NCP1377, an internal 8.0 s timer prevents the free−run frequency to exceed 100 kHz (therefore below the 150 kHz CISPR−22 EMI starting limit), while the skip adjustment capability lets the user select the frequency at which the burst foldback takes place. For NC1377B, the internal timer duration is reduced to 3.0 s to allow operation at higher frequencies (up to 300 kHz).

FEATUREs
• Free−Running Borderline/Critical Mode Quasi−Resonant Operation
• Latched Overvoltage Protection
• Auto−Recovery Short−Circuit Protection Via UVLO Crossover
• External Latch Triggering, e.g. Via Overtemperature Signal
• Current−Mode with Adjustable Skip Cycle Capability
• Internal 1.0 ms Soft−Start
• Internal Temperature Shutdown
• Internal Leading Edge Blanking
• 500 mA Peak Current Source/Sink Capability
• Under Voltage Lockout Level of 12.5 V (On) and 7.5 V (Min)
• Direct Optocoupler Connection
• SPICE Models Available for TRANsient Analysis
• Internal Minimum TOFF
• Pb−Free Packages are Available

Typical Applications
• AC−DC Adapters for Notebooks, etc.
• Offline Battery Chargers
• Consumer Electronics (DVD Players, Set−Top Boxes, TVs, etc.)
• Auxiliary Power Supplies (USB, Appliances, TVs, etc.)