NCP1234 Fixed Frequency Current Mode Controller for Flyback Converters The NCP1234 is a new fixedfrequency currentmode controller featuring Dynamic SelfSupply (DSS). This device is pintopin www.onsemi.com compatible with the previous NCP12xx families. The DSS function greatly simplifies the design of the auxiliary supply and the V capacitor by activating the internal startup current CC source to supply the controller during transients. SOIC7 Due to frequency foldback, the controller exhibits excellent CASE 751U efficiency in light load condition while still achieving very low standby power consumption. Internal frequency jittering, ramp MARKING DIAGRAM compensation, and a versatile latch input make this controller an 8 excellent candidate for converters where components cost is the key 34Xff constraints. ALYWX It features a timerbased fault detection that ensures the detection of overload independently of an auxiliary winding, and an adjustable 1 compensation to help keep the maximum power independent of the 34Xff = Specific Device Code input voltage. X = A or B Finally, due to a careful design, the precision of critical parameters ff = 65 or 100 is well controlled over the entire temperature range (40C to A = Assembly Location L = Wafer Lot +125C). Y = Year W = Work Week Features = PbFree Package FixedFrequency CurrentMode Operation with BuiltIn Ramp Compensation PIN CONNECTIONS 65 kHz or 100 kHz Oscillator Frequency version Latch18 HV Frequency Foldback then Skip Mode for Maximized Performance in Light Load and Standby Conditions FB 2 TimerBased Overload Protection with Latched (option A) or 3 V CS 6 CC AutoRecovery (option B) Operation GND 4 5 DRV Highvoltage Current Source with Dynamic SelfSupply, (Top View) Simplifying the Design of the V Capacitor CC Frequency Modulation for Softened EMI Signature, including during ORDERING INFORMATION Frequency Foldback mode See detailed ordering and shipping information in the package dimensions section on page 32 of this data sheet. Adjustable Overpower Compensation Latchoff Input for Severe Fault Conditions, Allowing Direct Connection of an NTC for Overtemperature Protection (OTP) V Operation up to 28 V, with Overvoltage Detection CC 500 mA Peak Source/Sink Current Drive Capability 4.0 ms SoftStart Typical Applications Internal Thermal Shutdown ACDC Adapters for Notebooks, LCD, and Printers PintoPin Compatible with the Existing NCP12xx Offline Battery Chargers Series Consumer Electronic Power Supplies These Devices are PbFree, Halogen Free/BFR Free and are RoHS Compliant Auxiliary/Housekeeping Power Supplies Semiconductor Components Industries, LLC, 2016 1 Publication Order Number: January, 2016 Rev. 2 NCP1234/DNCP1234 TYPICAL APPLICATION EXAMPLE VOUT VIN (dc) LATCH HV FB NCP1234 CS VCC GND DRV Figure 1. Flyback Converter Application Using the NCP1234 PIN FUNCTION DESCRIPTION Pin No Pin Name Function Pin Description 1 LATCH LatchOff Input Pull the pin up or down to latchoff the controller. An internal current source allows the direct connection of an NTC for over temperature detection 2 FB Feedback An optocoupler collector to ground controls the output regulation. 3 CS Current Sense This Input senses the Primary Current for currentmode operation, and Offers an overpower compensation adjustment. 4 GND IC Ground 5 DRV Drive output Drives external MOSFET 6 V V input This supply pin accepts up to 28 Vdc, with overvoltage detection CC CC 8 HV Highvoltage pin Connects to the bulk capacitor or the rectified AC line to perform the functions of Startup Current Source and Dynamic SelfSupply www.onsemi.com 2