onsemi NCP1234AD100R2G

The NCP1234 is a new fixed−frequency current−mode controller featuring Dynamic Self−Supply (DSS). This device is pin−to−pin compatible with the previous NCP12xx families. The DSS function greatly simplifies the design of the auxiliary supply and the VCC capacitor by activating the internal startup current source to supply the controller during transients. Due to frequency foldback, the controller exhibits excellent efficiency in light load condition while still achieving very low standby power consumption. Internal frequency jittering, ramp compensation, and a versatile latch input make this controller an excellent candidate for converters where components cost is the key constraints. It features a timer−based fault detection that ensures the detection of overload independently of an auxiliary winding, and an adjustable compensation to help keep the maximum power independent of the input voltage. Finally, due to a careful design, the precision of critical parameters is well controlled over the entire temperature range -40°C to +125°C. The NCP1234 includes all necessary features to build a safe and efficient power supply based on a fixed−frequency flyback converter. It is particularly well suited for applications where low part count is a key parameter, without sacrificing safety. Current−Mode Operation with slope compensation: The primary peak current is permanently controlled by the FB voltage, ensuring maximum safety: the DRV turn−off event is dictated by the peak current setpoint. It also ensures that the frequency response of the system stays a first order if in DCM, which eases the design of the FB loop. The controller can be also used in CCM applications with a wide input

• Fixed−Frequency Current−Mode Operation with Built−In Ramp Compensation
• 65 kHz or 100 kHz Oscillator Frequency version
• Frequency Foldback then Skip Mode for Maximized Performance in Light Load and Standby Conditions
• Timer−Based Overload Protection with Latched (option A) or Auto−Recovery (option B) Operation
• High−voltage Current Source with Dynamic Self−Supply, Simplifying the Design of the VCC Capacitor
• Frequency Modulation for Softened EMI Signature, including during Frequency Foldback mode
• Adjustable Overpower Compensation
• Latch−off Input for Severe Fault Conditions, Allowing Direct Connection of an NTC for Overtemperature Protection (OTP)
• VCC Operation up to 28 Vr, with Overvoltage Detection
• ±500 mA Peak Source/Sink Current Drive Capability
• 4.0 ms Soft−Start
• Internal Thermal Shutdown
• Pin−to−Pin Compatible with the Existing NCP12xx Series
• These Devices are Pb−Free, Halogen Free/BFR Free and are RoHS Compliant

• AC−DC Adapters for Notebooks, LCD, and Printers
• Offline Battery Chargers
• Consumer Electronic Power Supplies
• Auxiliary/Housekeeping Power Supplies