Description:

The NCP1253 is a highly integrated PWM controller capable ofdelivering a rugged and high performance offline power supply in atiny TSOP−6 package. With a supply range up to 28 V, the controllerhosts a jittered 65 kHz or 100 kHz switching circuitry operated in peakcurrent mode control. When the power on the secondary side starts todecrease, the controller automatically folds back its switchingfrequency down to a minimum level of 26 kHz. As the power furthergoes down, the part enters skip cycle while limiting the peak current.To avoid sub harmonic oscillations in CCM operation, adjustableslope compensation is available via the series inclusion of a simpleresistor in the current sense signal.Besides the auto−recovery timer−based short−circuit protection, anOver Voltage Protection on the VCC pin protects the whole circuitry incase of optocoupler destruction or adverse open loop operation.

Features:

• Fixed−Frequency 65 kHz or 100 kHz Current−Mode ControlOperation

• Frequency Foldback Down to 26 kHz and Skip−Cycle in Light LoadConditions

• Adjustable Ramp Compensation

• Internally Fixed 4 ms soft−start

• Timer−based Auto−Recovery or Latched Short−Circuit Protection

• Frequency Jittering in Normal and Frequency Foldback Modes

• Latched OVP on VCC

• Up to 28 V VCC Operation

• Extremely Low No−load Standby Power

• These are Pb−Free Devices

Typical Applications

• Ac−dc Converters for TVs, Set−top Boxes and Printers

• Offline Adapters for Notebooks and Netbooks