The NCP1238 is a new generation of the NCP12xx fixed−frequency current−mode controllers featuring Dynamic Self−Supply (DSS), pin−to−pin compatible with the previous generation.
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 its proprietary Soft−Skip™ mode combined with frequency foldback, the controller exhibits excellent efficiency in light load condition while still achieving very low standby power consumption. This Soft−Skip feature also dramatically reduces the risk of acoustic noise, which enables the use of inexpensive transformers and capacitors in the clamping network.

FEATUREs
• Timer−Based Overload Protections with Auto−Recovery (Option B) or Latched (Option A) Operation
• High−Voltage Current Source with DSS with Built−in Brown−out and Line Overvoltage Protections
• Fixed−Frequency Current−Mode Operation with Built−in Ramp Compensation
• Frequency Jittering for a Reduced EMI Signature
• Adjustable Overpower Compensation
• Latch−off Input for Severe Fault Conditions, with Direct Connection of an NTC for Overtemperature Protection (OTP)
• Protection Against Winding Short−Circuit
• Frequency Foldback transitioning into Soft−Skip for Improved Performance in Standby
• 65 kHz Oscillator (100 kHz and 133 kHz Versions Available Upon Request)
• VCC Operation up to 28 V
• Increased Precision on Critical Parameters
• ±1.0 A Peak Drive Capability
• 4.0 ms Soft−Start
• Internal Thermal Shutdown with Hysteresis
• These Devices are Pb−Free, Halogen Free/BFR Free and are RoHS Compliant*

Typical Applications
• ac−dc Adapters for Notebooks, LCD, and Printers
• Offline Battery Chargers
• Consumer Electronic Power Supplies
• Auxiliary/Housekeeping Power Supplies