Housed in a SOIC-7 or PDIP-7 package, the NCP1217 represents the second generation of NCP1203-based controllers. Thanks to its high drive capability, NCP1217 drives large gate-charge MOSFETs, which together with internal ramp compensation and built-in over voltage protection, ease the design of modern AC/DC adapters. NCP1217 offers a true alternative to UC384X-based designs.With an internal structure operating at different fixed frequencies (65, 100, 133kHz), the controller features a high-voltage start-up FET, which ensures a clean and loss less startup sequence. Its current-mode control topology provides an excellent input audio-susceptibility and inherent pulse-by-pulse control. Internal ramp compensation easily prevents subharmonic oscillations from taking place in continuous conduction mode designs.When the current setpoint falls below a given value, e.g. the output power demand diminishes, the IC automatically enters the so-called skip cycle mode and provides excellent efficiency at light loads. Because this occurs at a user adjustable low peak current, no acoustic noise takes place.The NCP1217 features two efficient protective circuitries: 1) in presence of an over-current condition, the output pulses are disabled and the device enters a safe burst mode, trying to re-start. Once the default has gone, the device auto-recovers. 2) if an external signal (e.g. a temperature sensor) pulls pin1 above 3.2V, output pulses are immediately stopped and the NCP1217 stays latched in this position. Reset occurs when the V collapses to ground, e.g. the user un-plugs the power supply.
●Features
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● Current-Mode with adjustable skip-cycle capability
● Built-in internal ramp compensation
● Auto-recovery internal output short-circuit protection
● Full latch-off if Adjustment pin is brought high
● Extremely low no-load standby power
● Internal temperature shutdown
● 500mA peak current capability
● Fixed frequency versions at 65kHz, 100kHz and 133kHz
● Direct optocoupler connection
● Internal Leading Edge Blanking
● SPICE models available for TRANsient and AC analysis
● Internal 1ms Soft start (A version only)
● Limited Duty Cycle to 50% (A version only)
● Pb-Free Packages are Available
