NCP1234AD65R2G Description

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 dramatically 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 conditions while still achieving deficient 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 constraint. 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).

NCP1234AD65R2G Features

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 V, 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

NCP1234AD65R2G  Applications

AC?DC Adapters for Notebooks, LCD, and Printers

Offline Battery Chargers

Consumer Electronic Power Supplies

Auxiliary/Housekeeping Power Supplies