1FEATURES
2• Critical Conduction Mode PFC
• Over-Voltage Protection
• Feedback Short Circuit Protection
• 70:1 PWM Decoded From Phase Dimmer
• Analog Dimming
• Programmable Dimming Range
• Digital Angle and Dimmer Detection
• Dynamic Holding Current
• Smooth Dimming Transitions
• Low Power Operation
• Start-Up Pre-Regulator Bias
• Precision Voltage Reference

APPLICATIONS
• Dimmable Downlights, Troffers, and Lowbays
• Large Form Factor Bulbs
• Indoor and Outdoor Area SSL
• Power Supply PFC

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