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The LM3450/50A is a power factor controller (PFC) with separate phase dimming decoder. The PFC regulates the output voltage while maintaining excellent power factor. The phase dimming decoder interprets the phase angle and remaps it to a 500Hz PWM output. This device is ideal for implementing a dimmable off-line LED driver for 10-100W loads.

The phase dimming decoder has several unique features. The input-output mapping is programmable for design flexibility, while a dynamic filter and variable sampling rate provide smooth uniform dimming. A dynamic hold circuit ensures that the phase dimmer angle is decoded properly while minimizing extra power loss.

The LM3450A is identical to the LM3450 with the exception of one circuit operation. The dynamic hold current is sampled in the LM3450 while it continuously operates in the LM3450A. This difference between the two devices defines the suitable applications for each. The following is a general guideline for choosing the correct device:

• Any 120V designs with P_OUT > 15W - LM3450A
• Any 230V designs with P_OUT > 25W - LM3450A
• 120V 2-Stage designs with P_OUT < 15W - LM3450
• 230V 2-Stage designs with P_OUT < 25W - LM3450